www.sinfoton-cm.es

L

I

B

R

O

D

E

A

B

S

T

R

A

C

T

S

1ª FERIA DE OTOÑO

SINFOTÓN

Aula de Grados (Ed. Padre Soler)

Universidad Carlos III de Madrid

(Campus de Leganés)

23 Octubre 2015

Programa SINFOTÓN

S2013/MIT-2790

Comité Organizador

Juan Luis García Pomar (CSIC)

garciapomar@io.cfmac.csic.es

Gonzalo del Pozo (URJC) gonzalodpm@gmail.com

Laura Monteagudo (UAH) laura.monteagudo@depeca.uah.es

Antonio Pérez-Serrano (UPM) antonio.perez.serrano@upm.es

Pedro Contreras (UC3M) pcontrer@ing.uc3m.es

i

ii

Prólogo

Esta primera Feria de Otoño de Jóvenes investigadores del programa de

actividades Sensores e INstrumentación en tecnologías FOTÓNicas (SINFOTON)

supone un punto de encuentro entre sus investigadores y algunas empresas

interesadas en sus objetivos. Además, se celebra en 2015, el año que ha sido

declarado por la Organización de las Naciones Unidas 'Año Internacional de la Luz

y las Tecnologías Basadas en la Luz'. Dado que el programa busca desarrollar

sistemas de instrumentación y sensores a partir de tecnologías fotónicas con una

clara vocación de aplicación en diferentes sectores industriales; a través de sus

actividades, se refuerza el objetivo de esta celebración en la que se busca que la

población en general tome conciencia de la importancia de las tecnologías

basadas en la luz en nuestra vida cotidiana y de su importancia para el desarrollo

sostenible del planeta, más allá de que la luz haya sido imprescindible para el

desarrollo de la vida tal y como la conocemos.

La idea de desarrollar una Feria de Otoño organizada por los jóvenes

investigadores tiene su origen en mi experiencia en el Research Laboratory of

Electronics del Instituto Tecnológico de Massachusetts donde observé cómo

interactuaban de forma exitosa los diferentes grupos de investigación del centro

de forma distendida a través de la iniciativa de los más jóvenes que eran el eje del

encuentro. Es por ello que espero que nuestra Feria de Otoño de Jóvenes

investigadores también permita aumentar el conocimiento de los diferentes grupos

de forma que surjan potenciales colaboraciones o nuevas ideas.

Para aquellos que es la primera vez que ven sus siglas, SINFOTÓN es un Programa

de Actividades de I + D entre grupos de investigación de la Comunidad de Madrid

(CM), financiado en la convocatoria Tecnologías 2013, y cofinanciado con Fondos

Estructurales. El consorcio está formado por grupos de 4 universidades públicas (U.

Carlos III de Madrid, U. Politécnica de Madrid, U. Alcalá, U. Rey Juan Carlos), 1

grupo del Consejo Superior de Investigaciones Científicas y 3 laboratorios de la Red

de Laboratorios de la CM. En total actualmente participan 76 investigadores y

cuenta además con 25 grupos y 17 empresas externas asociadas. En cuanto a su

temática, la experiencia de los grupos participantes en el diseño de láseres de alta

potencia, los sistemas de instrumentación con fibras ópticas, la fotónica orgánica y

asistencial, la óptica integrada y las tecnologías de cristal líquido se ponen al

servicio de la sociedad para abordar los retos propuestos en Horizonte 2020,

relacionados con la salud, la seguridad alimentaria, la energía, el transporte, el

clima y la sociedad. Todo ello a través de seis objetivos específicos. Así nuestras

soluciones podrían mejorar la seguridad de infraestructuras críticas, evitando daños

como los ocasionados recientemente con el corte de fibra óptica en la red de alta

velocidad.

iii

En cuanto al formato, se ha optado por una sesión de mañana dedicada a

presentar los datos más relevantes de SINFOTON y de DIFRAGEOS-CM, otro Programa

de Actividades de CM con cierta afinidad temática. También se incluye una

conferencia invitada a cargo Prof. Joseba Zubia, investigador asociado del

consorcio y un conjunto de charlas y una mesa redonda a cargo de empresas

interesadas en el consorcio. En la sesión de tarde, se cuenta con una exhibición de

las empresas interesadas y la presentación de pósteres por parte de los jóvenes

investigadores.

Por último, este libro de resúmenes recoge las contribuciones de todos aquellos

jóvenes investigadores que presentan sus trabajos en la Feria de Otoño. Esperemos

que con ello se dinamice la colaboración entre los grupos que participan en

SINFOTON, al promover nuevas colaboraciones a través de los más jóvenes,

mejorando la productividad y el alcance de los proyectos a desarrollar.

Desde el grupo de Displays y Aplicaciones Fotónicas de la Universidad Carlos III de

Madrid, os deseamos a todos una Jornada provechosa e interesante.

Carmen Vázquez, Madrid, Octubre 2015

AGENDA

iv

Hora Actividad

10:00

Presentación de la jornada y de SINFOTÓN-CM

Carmen Vázquez

(UC3M, Coordinadora general de Consorcio SINFOTÓN-CM)

10:30

Presentaciones de empresas invitadas I

A cargo de:

Sonia Martín Lopéz - Focus S.L.

Beatriz Cerrolaza - Alise Devices S.L.

Juan Barbero - Alter Technology TÜV Nord S.A.U.

11:15 Presentación del consorcio DIFRAGEOS-CM

Daniel Segovia Vargas (UC3M)

11:45 Pausa para Café

12:15

Presentación Invitada

Plastic Optic Fiber Sensors for Aeronautical Structural Health

Monitoring

Joseba Zubia (Universidad del País Vasco)

13:00

Presentaciones de empresas invitadas II

A cargo de:

Ana Manzanares Ituarte - Greenlight Solution S.L.

Rubén Criado - Luz Wavelabs

13:30

Mesa Redonda

Diferentes perspectivas sobre carreras en las tecnologías

fotónicas, con

Mariafernanda Vilera (UPM)

Ana Manzanares Ituarte (Greenlight Solution S.L.)

José Manuel Sánchez Pena (UC3M)

Jorge Ripoll (4Dnature)

Pedro Corredera (CSIC) (Moderador)

14:15 Pausa para Comida

15:30

Sesión de posters (31 contribuciones)

a cargo de los jóvenes investigadores del consorcio

Exhibición de empresas

Café

17:30 Clausura

ÍNDICE DE ABSTRACTS

Ponente Grupo/Laboratorio Pág.

García Cámara, Braulio GDAF-UC3M 1

Sánchez Montero, David GDAF-UC3M 2

Contreras Lallana, Pedro GDAF-UC3M 3

Tapetado Moraleda, Alberto GDAF-UC3M 4

Pinzón Castillo, Plinio Jesús GDAF-UC3M 5

Algorri Genaro, Jose Francisco GDAF-UC3M 6

Torrecilla Rosell, Javier GDAF-UC3M 7

Vega Colado, César GDAF-UC3M 8

Marzal Beneyto, Vicente GDAF-UC3M 9

Poudereux Sánchez, David CEMDATIC-UPM 10

Vilera Suárez, María Fernanda CEMDATIC-UPM 11

Pérez Serrano, Antonio CEMDATIC-UPM 12

Caño García, Manuel CEMDATIC-UPM 13

García Pomar, Juan Luis DETFO-CSIC 14

Velázquez Molinero, José Luis DETFO-CSIC 15

Borreguero Martín , Elisa DETFO-CSIC 16

v

ÍNDICE DE ABSTRACTS

Ponente Grupo/Laboratorio Pág.

Villafranca Velasco, Aitor DETFO-CSIC 17

Pulido de Torres, María Concepción DETFO-CSIC 18

Galindo Santos, Juan DETFO-CSIC 19

Rosa, Pawel DETFO-CSIC 20

Nuño del Campo, Javier DETFO-CSIC 21

Nuñez Cascajero, Arántzazu GRIFO-UAH 22

Monteagudo Lerma, Laura GRIFO-UAH 23

Jiménez Rodríguez, Marco GRIFO-UAH 24

López Gil, Alexia Inés GRIFO-UAH 25

Domínguez López, Alejandro GRIFO-UAH 26

Pastor Graells, Juan GRIFO-UAH 27

Angulo Vinuesa, Xabier GRIFO-UAH 28

de Andrés Rubio, Ana GRIFO-UAH 29

Valdueza Felip, Sirona GRIFO-UAH 30

del Pozo Melero, Gonzalo LAB169-URJC 31

Bernad Gracia, Berta LAB2-CSIC 32

vi

vii

ABSTRACTS

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

An all optical nanometric switch Braulio García-Cámara1�, J. Francisco Algorri1, Alexander Cuadrado2, Virginia Urruchi1, José

Manuel Sánchez-Pena1,Rosalía Serna2 and Ricardo Vergaz1

1Displays and Photonic Applications Group (GDAF-UC3M), Carlos III University of Madrid, Leganés , Spain 2Laser Processing Group, Instituto de Óptica-CSIC, Madrid, Spain

�Corresponding author e-mail: brgarcia@ing.uc3m.es

Keywords (3): Nanoparticles, scattering, metadevices.

Abstract

Current requirements on information transfer, computation and storage demand new counterparts to the electronic components. In particular, full-optical components are currently explored. Different phenomena observed in the interaction of light with nanoparticles allow the development of this concept. In this work, we explored the possibility of creating a full optical nanometric switch to be the simplest part of the future family of components in optical nanocircuits.

In 80’s, Kerker et al [1] showed that the scattering of sub-wavelength particles can be directed under certain conditions. In fact, a nanoparticle can accomplish a zero backscattering (ZB) or minimum forward scattering (MF) depending on the relationship between its material, size and incident wavelength. We have demonstrated that the Kerker conditions can be found in the visible range for several usual semiconductor materials, as Silicon, Germanium, TiO2, GaAs, etc [2]. Playing with sizes, it is possible to obtain nanoparticles satisfying either the ZB or the MF at the same wavelength. Then, we have proposed a dimer of silicon nanoparticles [3] presenting such combination of directional scattering in the visible range. This set can produce either a maximum or a minimum of the scattered field in the area between the nanoparticles. As Kerkers’ conditions are very dependent on the wavelength, we propose that a modulation of the incident wavelength can be used as switching parameter (Fig. 1). We have searched the optimum parameters of the dimer setup, in wavelength, distance between particles and their sizes, in order to make easier the fabrication for the Research Community to get an experimental Proof of Technology of these simple designs.

Fig. 1. Scheme of the proposed nanoswitch based on a dimer of silicon nanoparticles. Switching the incident wavelength of the light, a hotspot can be modulated in the gap between them

Acknowledgements. This work has been supported by Ministerio de Economía y Competitividad of Spain (grants no. TEC2013-47342-C2-2-R, TEC2012-38901-C02-01 and no.TEC2013-50138-EXP) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid.

References

[1] M. Kerker, D.S. Wang, and C.L. Giles. “Electromagnetic Scattering by Magnetic Spheres,” J. Opt. Soc. Am. 73, 765-767(1983).[2] B.García-Cámara, J.F. Algorri, A. Cuadrado, V. Urruchi, J.M. Sánchez-Pena, and R. Vergaz, “Size Dependence of theDirectional Scattering Conditions on Semiconductor Nanoparticles,” IEEE Photonic Technol. Lett. 27, 2059-2062 (2015).[3] B. García-Cámara, J. F. Algorri, A. Cuadrado, V. Urruchi, J. M. Sánchez-Pena, R. Serna, R.Vergaz. “All-Optical NanometricSwitch based on the Directional Scattering of Semiconductor Nanoparticles,” J. Phys. Chem. C 119, 19558-19564 (2015).

Ver póster 1

Effects of elongation and impact measurements on plastic optical fibers

D.S. Montero1, J.C. Torres1, J.L. Pérez-Castellanos2 and C. Vázquez1

1Grupo de Displays y Aplicaciones Fotónicas, Dpto. Tecnología Electrónica, Universidad Carlos III de Madrid, Leganés, Madrid, Spain

2Dpto. De Mecánica de Medios Continuos y Teoría de Estructuras, Universidad Carlos III de Madrid, Leganés, Madrid, Spain

Corresponding author e-mail: dsmontero@ing.uc3m.es

Keywords (3): Plastic optical fiber, intensity-based sensor, elongation, impact measurements

Abstract

As the optical power transmitted by an optical fiber under tensile stress varies with strain, it can be used a sensor for strain/impact/vibration monitoring in structural elements (SHM). In this work quasi-static tensile tests of Step Index Plastic Optical Fibers (SI-POFs) are described. Young’s modulus, yield stress and tensile strength are derived and discussed from the experimental tests. The contribution of both elastic and plastic strain components to the optical power loss is reported. Additionally, preliminary results of impact measurements over POF specimens are introduced showing the capability of this sensing technique to detect and evaluate the impact strength suffered by a structure. It is expected in the near future to incorporate the proposed technique in aerospace vehicles to monitor possible impact on their composite materials.

The following figures show some results that have been obtained. Fig. 1 illustrates the measured stress-strain (σ-ε) curve obtained in a 0.0005s-1 strain rate test of a standard SIPOF (980μm/1mm core/cladding diameter, PMMA core material) as well as self-manufactured POF specimens to perform the strain and impact tests.

(a)

Left (b) Right

Fig. 1. (a)Measured σ-ε curve obtained in a 0.0005s-1 strain rate test. (b) POF specimen and mounting scheme(left); surface

mounted POF sensor in a composite material for impact tests (right).

Fig. 2(a) depicts the normalized received optical power versus strain in tensile tests at different strain rates. It is observed an optical power decrease around 15-20% while deformation increases up to specimen breakage. Fig. 2(b) shows the received signal (voltage) in a 20N impact force test. After a transient time, the received signal reaches its original value (prior to the impact). This fact leads us to think that the POF sensor can operate under elastic regimes, being able to recover its original shape. Both tests demonstrate the viability of performing light intensity measurements in POFs with strain (elongation) conditions for sensing purposes.

(a)

(b)

Fig. 2. (a)Normalized received optical power versus strain in tensile test at different strain rates. (b) Detected signal at

reception during impact test.

2 Ver póster

Tap and Two Split Traffic Grooming Switch based on Integrated Optics P.C.Lallana1, G. M. Fernández 2, D. Larrabeiti2 and C. Vázquez1

1Display and Photonics Applications Group, Universidad Carlos III de Madrid, Leganés, Spain 2Advanced Switching and Communication Systems, Universidad Carlos III de Madrid, Leganés, Spain

Corresponding author e-mail: pcontrer@ing.uc3m.es

Keywords (3): Configurable ring resonator, integrated optics, Mach Zehnder interferometer.

Abstract

There are a huge number of applications that require high bandwidth and multipoint delivery. The use of wavelength multiplexing division (WDM) and optical switching has allowed fulfilling their bandwidth demand. However, there is still a lack of support of multicast at the optical layer in commercial WDM products, even though there are many technological options [1].

In this contribution, we propose to enhance the structure proposed in [2] with grooming and binary packet switching capabilities. From the perspective of light-trails, this architecture can be seen as a multipoint light-trail approach. Each packet that enters in the optical switch is assumed to be labeled with a header (or signal e.g. [3]) indicating the destination(s) and its length. The incoming label is read and interpreted before the packet enters to the optical switch and according to it the packet is forwarded over one or two outputs, or simply erased if the node is the last destination for the packet in the light-trail. If the packet is erased, it is possible to add both unicast and multicast packets downstream this multipoint light-trail.

The structure of the optical switch is shown in Fig. 1. It is composed of a coupler and a delay line made in optical fiber, followed by a Mach Zehnder Interferometer and two configurable Ring Resonators implemented in integrated optics. With this structure, the proposed optical switch is capable of performing up to six functionalities (Fig. 2): Tap-and-Continue, Tap-and-Continue-and-Add, Tap-and-Two-Split, Tap-and-Erase, Tap-and-Add and Tap-and-Two-Add.

Fig. 1. Structure of the proposed Tap 2-Split Traffic Grooming Switch.

Fig. 2. Switch functionalities:

(a) Tap & Continue, (b) Tap & Continue & Add, (c) Tap & Two Split, (d) Tap & Erase,

(e) Tap & Add, (f) Tap & Two Add.

According to the simulations carried out, 4.83dB insertion losses can be achieved when the node is configured in Tap and Two split operation mode, 1.08dB or 2.58dB insertion losses can be obtained in Tap and Continue mode, depending on the output port. In the case of Only Tap operation, an attenuation of 22.22dB is provided.

Acknowledgements. This work was partially supported by the Spanish Ministry projects TEC2012-37983-C03-02 and TEC2012-38362-C03-01. Additional support from SINFOTON-CM (grant no. S2013/MIT) and TIGRE5-CM (grant no. S2013/ICE-2919).

References [1] Y. Zhou. and G-S. Poo, "Optical multicast over wavelength-routed WDM networks: A survey", Optical Switching and

Networking, vol. 2, no. 3, pp 176–197, Nov. 2005. [2] G. Fernández del Carpio, C. Vázquez, P. Contreras, D. Larrabeiti, "Tap-and-2-Split Switch Design Based on Integrated

Optics for Light-Tree Routing in WDM Networks", IEEE/OSA J. Lightwave Tech., vol. 27, no. 13, pp. 2506–2517, Jul.2009. [3] T. Koonen, T. Sulur, I. T. Monroy, J. Jennen, and H. D. Waardt, "Optical labeling of packets in IP-Over-WDM Networks", in

Proc. ECOC 2002, Paper 5.5.2.

Ver póster 3

Optical Fiber Pyrometer Positioning Accuracy during Machining

A. Tapetado1, J. Díaz-Álvarez2, E. García1, H. Miguélez3 and C. Vázquez1

1Electronics Technology Dpt., Carlos III University of Madrid, Leganés, Spain 2Aerospace Engineering Dpt., Carlos III University of Madrid, Leganés, Spain

2Mechanical Engineering Dpt., Carlos III University of Madrid, Leganés, Spain Corresponding author e-mail: atapetad@ing.uc3m.es

Keywords (3): Two-colour pyrometer, Machining process, Fiber-optic.

Abstract

An important problem using optical fiber in machining is the accurate position of the optical fiber

end below the major cutting edge. Few hundred microns distance to cutting surface and a very

difficult to access area under operating conditions limits the potential to use dedicated optics to

improve light collimation and coupling.

The system achieves good spatial resolution by placing the fiber close to the target and below

the tool insert. This can be shown in Fig. 1. The fiber is adjusted to the desired measurement position

and fixed in a notch of the shim with a nut. The maximum distance between fiber end and machined

surface is 2mm.

A set of measures are carried out to evaluate the effect of the distance between the fiber end

and the target during the machining process, see Fig. 2. Radiance emitted by the blackbody is

measured at a wavelength of 1.3 and 1.55μm by two photodetectors (PDs). The temperature of the

blackbody is fixed at 650ºC to ensure sufficient light power to avoid the PD noise at low temperatures.

Using a positioning stage, the distance between the blackbody and the fiber end is changed from

0.2 to 2mm. A total of 10 set of measurements for each distance have been carried out to perform

a statistical analysis.

The experimental results are compared with a theoretical model [1] to validate the coherence of

the measurements, see Fig. 2. The light power measured by each photodetector is calculated from

a distance of 0 to 2mm at 0.5mm intervals. The temperature is fixed at 650ºC. The pyrometer design

parameters considered in the simulation are reported in [2].

Fig. 1. Visualization of the distance between the optical

fiber end and the workpiece (tool insert is removed).

Fig. 2. Optical power measured by the PDs versus distance

for a wavelength of (circle) 1.3μm and (square) 1.55μm:

(Non-filled) Simulations, (Filled) Measurements.

Fig. 2 shows a deviation between the theoretical and experimental curves of 9.5 and 7.5pW for

filtering channels of 1.3 and 1.55μm, respectively. Thus, considering a sensor power accuracy of 1.1

and 3.4pW [2], respectively, the power deviations are within photodetector power accuracy. These

results demonstrate that the measured absolute temperature is independent of the distance

between the fiber end and the target.

Acknowledgements. This work was supported by the Spanish Ministry of Economía y

Competitividad under grant TEC2012-37983-C03-02, P2013/MIT-2790 and DPI2014-56137-C2-2.

References

[1] T. Ueda, A. Hosokawa, and A. Yamamoto, "Studies on Temperature of Abrasive Grains in Grinding-Application of Infrared

Radiation Pyrometer," Journal of Engineering for Industry 107, 127 (1985).

[2] A. Tapetado, "Fiber Optic Sensors and Self-reference Techniques for Temperature Measurements in Different Industrial

Sectors," Carlos III University of Madrid (2015).

4 Ver póster

Data transmission system based on visible wavelength division

multiplexing at 3-Gb/s over plastic optical fiber

Plinio Jesús Pinzón, Carmen Vázquez, and Isabel Pérez

Grupo de Displays y Aplicaciones Fotónicas (GDAF), Universidad Carlos III de Madrid, Leganés, España. Corresponding author e-mail: ppinzon@ing.uc3m.es

Keywords (3): Gigabit Ethernet, polymer optical fiber, Visible wavelength division multiplexing.

Abstract

After exploiting the capabilities of single channel transmission [1], visible wavelength division

multiplexing (visible WDM) is proposed as a solution to expand the transmission capacity of SI–POF

based systems. To date, there are several proposals of modulation methods [1], spectral grids [2]

and multiplexer/demultiplexer devices [3] that allow to implement transmission systems based on

visible WDM at data rates of Multi−Gb/s over SI−POF links. In this paper, the design of a real−time

visible WDM system over SI−POF for an efficient performance in terms of Ethernet Throughput ×

Length (T×L) is presented. The system performance is tested using the extremes channels of the 3–

channel available grid.

Fig. 1. Transmission scheme of the proposed SI–POF visible WDM system with 3 channels between 400 and 700 nm.

The objective is to obtain a real−time link between two points (client and server) at data rates of

3−Gb/s using 3 channels, as is shown on Fig. 1 scheme. The PCs are equipped with Gigabit Ethernet

interfaces in combination with Media Converters (MCs) used to generate and to read the

transmitted data bits, respectively. In the transmitters (Txs), the different Tx−signals modulate the

Laser Diode (LD) of the respective channel. A fiber bundle based multiplexer (Mux) transmits the 3

channels over the SI–POF link of 50 m, and a diffraction grating based demultiplexer (DeMux) splits

the different channels to their respective receivers (Rxs) at the end of the link.

The performance of the proposed visible WDM link has been evaluated using channels ch1 and

ch3. In both channels, the transmission speed of the physical layer (PHY rate) is 1035.78 Mb/s, for

1Gb/s data rate, with BER < 1×10–10, which represents an error free transmission. The system has the

potential of expanding the transmission data rate up to 3 Gb/s in longer distances, with better

Ethernet Throughput than recent proposals [4]. This represents a real improvement in the

performance of commercial and experimental SI−POF transmission systems.

Acknowledgements. This work has been sponsored by the Spanish institutions Ministerio de

Economía y Competitividad under project TEC2012–37983–C03–02, Comunidad de Madrid under

grant S2013/MIT–2790.

References

[1] C. M. Okonkwo et al., “Recent results from the EU POF−PLUS project: multi−Gigabit transmission over 1 mm core diameter

plastic optical fibers,” J. Lightwave Technol., 29, 186–193, 2011.

[2] M. Jončić et al., “Investigation on spectral grids for VIS visible WDM applicationsover SIPOF,” in Proceedings of ITG

Symposium: Photonic Networks, pp. 1-6, 2013.

[3] P. J. Pinzón et. al., ” Efficient Multiplexer/Demultiplexer for Visible WDM Transmission over SI-POF Technology,” J. Lightwave

Technol., 33, 3711–3718, 2015

[4] R. Kruglov et al., “21.4 Gb/s discrete multitone transmission over 50-m SI-POF employing 6-channel visible WDM,” in

Proceedings of OFC, pp. 1-3, 2014.

Ver póster 5

Micro-optical phase modulators based on liquid crystal technology

J.F. Algorri1, V. Urruchi1, N. Bennis2, J.M. Sánchez-Pena1 and J.M. Otón2

1GDAF, Dpto. Tecnología Electrónica, E.P.S., Universidad Carlos III, Leganés, Madrid, Spain 2CEMDATIC, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid, Madrid, Spain Country

Corresponding author e-mail: jalgorri@ing.uc3m.es

Keywords: Liquid crystals, optical phase modulator, micro-optical elements.

Abstract

Liquid crystals (LCs) have been the subject of numerous developments during the past 50 years.

In some areas have competed with other materials, but in other cases, their anisotropic properties

easily modifiable through the application of external fields (mechanical, electric or magnetic) are

unique. Therefore, now and in the future LCs will be the protagonists of a multitude of applications,

mostly non-related with displays (LCDs). Today, there are wide variety of research lines open. For

example, optical communications, microwave and terahertz, nanotechnology, medicine, biology

and biochemistry, security, sensors and optical phase modulators.

An optical phase modulator is an optical element used to control the phase of light. They have

multiple applications, for example ophthalmological applications, tunable zooms, beam steering,

correction of aberrations, astronomy, 3D vision applications, etc. The displays and photonics

application group (GDAF) of Carlos III university of Madrid (UC3M) in collaboration with CEMDATIC

of Polytechnic University of Madrid (UPM) have extended the knowledge in this field by the proposal

of several advanced micro-optical phase modulators. These, obtain with simply topologies either

common optical elements, e.g. microlenses for autostereoscopic devices [1], aberration controllers

for rectangular micro-optical elements [2] and microlenses with reduced aberrations and tunable

rotation [3], or singular optical elements, e.g. micro-axicon arrays [4], tunable prisms [5] and tunable

optical vortices [6].

Fig. 1. Focusing capabilities of the proposed devices, (a) rotary lens, (b) Bessel beams of the microaxicon array and (c)

tunable optical vortex.

The proposed devices have several advantages over classic optical elements. For example, they

are tunable, easy to fabricate and low cost. Moreover, owing to the continuous optical phase shift

of these devices, the light efficiency is improved with respect to other technologies based on spatial

light modulators (SLM). These devices can be very useful in novel applications (e.g. OAM fiber optics

communications, atom manipulation, generation of Bessel beam arrays, etc.).

Acknowledgements. TEC2013-47342-C2-2-R and SINFOTON S2013/MIT-2790.

References

[1] J. F. Algorri, V. Urruchi, J. M. Sánchez-Pena, J. M Otón, "An Autostereoscopic Device for Mobile Applications Based on a

Liquid Crystal Microlens Array and an OLED Display,” J. Disp. Technol., vol. 46, no. 4, pp. 327-336 (2014).

[2] J. F. Algorri, V. Urruchi, N. Bennis, J. M. Sánchez-Pena, and J. M. Otón, “Tunable liquid crystal cylindrical micro-optical

array for aberration compensation,” Opt. Express, vol. 23, no. 11, pp. 13899–13915 (2015). [3] J. F. Algorri, V. Urruchi, N. Bennis, and J. M. Sanchez-Pena, “Cylindrical liquid crystal microlens array with rotary axis and

tunable capability,” IEEE Electron Device Lett., vol. 36, no. 6, pp. 582-584 (2015). [4] J. F. Algorri, V. Urruchi, N. Bennis, and J. M. Sanchez-Pena, “Modal liquid crystal microaxicon array,” Opt. Lett., vol. 39, no.

12, pp. 3476–9 (2014).

[5] J. F. Algorri, G.D. Love, V. Urruchi, "Modal liquid crystal array of optical elements,” Opt. Express, vol. 21, no. 21, pp. 24809–

24818 (2013).

[6] J. F. Algorri, V. Urruchi, B. Garcia-Camara, and J. M. Sanchez-Pena, “Generation of Optical Vortices by an Ideal Liquid

Crystal Spiral Phase Plate,” IEEE Electron Device Lett., vol. 35, no. 8, pp. 856–858 (2014).

6 Ver póster

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Microstrip dual-mode patch resonators for tuning the spectral response

of liquid crystal band-pass filters filters

Javier Torrecilla1, Virginia Urruchi1, and José Manuel Sánchez-Pena1

1Grupo de Displays y Aplicaciones Fotónicas, Dpto. Tecnología Electrónica, Universidad Carlos III, C/Butarque

15, E28911 Leganés, Madrid, Spain

Corresponding author e-mail: jtorreci@ing.uc3m.es

Keywords (3): liquid crystal, microwave filters, microstrip technology.

Abstract

For more than two decades, liquid crystals (LC) have been used for designing tunable devices

at the microwave band of frequencies (300 MHz – 300 GHz) because of the dielectric anisotropy of

their molecules [1]. The ability of LC of achieving large tuning ranges with low cost and power

consumption makes them very suitable for this goal. Since band-pass filters are essential devices in

microwave telecommunications systems, there has been a growing interest in the study of LC-

based band-pass filter whose central frequency can be voltage-controlled [2].

In this work, we consider two approaches for implementing tunable LC band-pass filters based

on microstrip dual-mode technology. The filters were designed, manufactured, and characterized,

and their spectral performance compared at microwave frequencies. The alternative designs were

derived from twin microstrip resonators in which the patch was reshaped. All filters were filled with

the same commercial nematic LC. The first approach, designed by using a conventional microstrip

dual-mode pattern [3], achieved a filter frequency tuning from 4.77 GHz to 5.11 GHz. The second

proposal demonstrated that performance of the band-pass spectral response can be refined in

terms of return loss. In those embodiments, the conventional dual-mode patch has been

strategically reshaped aiming a significant reduction of return loss by decreasing the filter

bandwidth. The comparison between the two schemes has revealed a decrease of the return loss

up to 63% for the implementation with a square cut in a corner of the patch.

References

[1] D. Dolfi , M. Labeyrie, P. Joffre and J. P. Huignard, “Liquid crystal microwave phase shifter”, Electronics Letters, Vol. 29 No.

10, pp. 926-928, (1993).

[2] F. Goelden, A. Gaebler, O. Karabey, M. Goebel, A. Manabe and R. Jakoby, "Tunable band-pass filter based in liquid

crystal" German Microwave Conference, pp. 98-101, (2010).

[3] S. Li, H. Cai, W. Wu, Y. Li and Z. Wang, “New dual-mode microstrip bandpass filter with a square notch”, IEEE ICCT, pp.

656-658, 2010.

Ver póster 7

Nuevas ayudas técnicas en rehabilitación visual

C. Vega1, R. Vergaz1, A. Viñuales2, R. Cuadrado3, R. Coco3, B. Coco3, S. Peris4, P. Artús4 1Grupo de Displays y Aplicaciones Fotónicas, Universidad Carlos III de Madrid, Madrid, Spain

2Centro de Tecnologías Electroquímicas (CIDETEC), Parque Tecnológico de San Sebastián, Spain 3Instituto de Oftalmobiología Aplicada, Universidad de Valladolid, Valladolid, Spain

4INDO Lens Group, Departamento I+D, SantCugat del Vallés, Barcelona, Spain Autor e-mail: cesar.vega@uc3m.es

Keywords (4): Cristal Electrocrómico, Baja Visión, ayuda técnica, gafas

Abstract

Dispositivos electrocrómicos han sido usados e incluso comercializados, en los últimos años, como ventanas inteligentes o como retrovisores en los coches [1-2]. Sin embargo, su uso como filtros ópticos para la visión, aunque se ha intentado desde de los años ochenta [3-6], no ha llegado nunca a comercializarse. Por otro lado, aunque no haya un total acuerdo entre los profesionales de la oftalmología [7], algunas investigaciones han mostrado que el uso de filtros, al eliminar ciertas longitudes onda, podría ser muy beneficioso para todo tipo de personas [8]. Desde aquellos que simplemente los quieran usar como gafas de sol de coloración variable, hasta personas con baja visión cuya patología los hace extremadamente sensibles a cambios bruscos de luz-oscuridad. Éstas necesitan llevar siempre consigo una serie de filtros, normalmente entre dos y cuatro con el inconveniente que esto les genera. En la actualidad sólo existe una solución comercial de funcionamiento similar, las lentes fotocromáticas, las cuales cambian de coloración al recibir radiación ultravioleta. Esto significa que cambian de color con la incidencia directa de radicación solar, pero no funcionan en lugares donde esta radiación no existe, como interiores o donde es filtrada como la mayoría de los coches. Además presentan otro inconveniente como es su baja velocidad de conmutación, siendo del orden de varios minutos [9]. Se ha desarrollado un sistema capaz de aplicar diferentes algoritmos, configurables mediante una interfaz de usuario, a un cristal electrocrómico el cual almacena automáticamente, la tensión aplicada, la transmitancia, la temperatura y la corriente consumida, en uno o varios ficheros compatibles con Microsoft Excel para su posterior procesado. De este modo, se describirán los resultados de distintos algoritmos aplicados a diferentes cristales electrocrómicos. Se mostrarán tiempos de respuesta, variación de la transmitancia y consumo eléctrico con el objetivo de aplicar el algoritmo óptimo en relación con su consumo/tiempo de conmutación sobre los cristales de un nuevo dispositivo de ayuda a la visión desarrollado por el autor del presente trabajo. Mejores tiempos de respuesta serán mostrados frente a las lentes fotocromáticas. También se mostrará cómo es posible integrar la electrónica en una montura de gafas similar a las actuales soluciones comerciales.

References [1] Harlan J. Byker, Gentex Corporation, "Single-compartment, self-erasing, solution-phase electrochromic devices, solutions for use therein, and uses thereof”, U.S. Patent No.4,902,108, (1990).

[2] [online] at https://www.gentex.com/automotive/products/driver-safety (23/09/2015)

[3] Monk, P. M. S., Mortimer, R. J., & Rosseinsky, D. R. [Electrochromism and electrochromic devices] Cambridge: Cambridge University Press (2007).

[4] Harlan J. Byker, Gentex Corporation, "Single-compartment, self-erasing, solution-phase electrochromic devices, solutions for use therein, and uses thereof”, U.S. Patent No.4,902,108, (1990).

[5] Chao Ma, Chunye Xu, "Smart goggles based on all-plastic electrochromic devices", Proceedings of SPIE Vol. 7493, 74931C (2009).

[6] Chao Ma, Minoru Taya, Chunye Xu, "Smart sunglasses with tunable shade", Proceedings of SPIE Vol. 6927, 69271J (2008)

[7] Eperjesi, F., Fowler, C. W., Evans, B. J., “Do tinted lenses or filters improve visual performance in low vision? A review of the literature,” Ophthalmic Physiol Opt., 22(1), 68-77 (2002).

[8]C. Sanchez-Ramos. Tesis doctoral “Filtros ópticos contra el efecto fototóxico del espectro visible en la retina: Experimentación animal” Universidad Europea de Madrid, 2010

[9][online] www.Zeiss.es. http://www.zeiss.es/vision-care/es_es/better-vision/mejor-vision-con-zeiss/tus-lentes-individualizadas-zeiss/oscurece-rapido-Se-aclara-rapido-Las-lentes-fotosensibles-de-ZEISS.html (23/09/2015)

8 Ver póster

Simulación de las propiedades ópticas de cristales líquidos dopados con nanopartículas resonantes

V. Marzal Beneyto*, B. García-Cámara, I. Pérez Garcilópez, J.M. Sánchez-Pena

Grupo de Displays y Aplicaciones Fotónicas (GDAF-UC3M), Dpto. Tecnología Electrónica, Universidad Carlos III de Madrid, C/Butarque 15, E28911 Leganés, España

*vmarzal@ing.uc3m.es

Keywords : cristal líquido, nanopartículas, resonancias

Abstract

Los cristales líquidos (CL) son ampliamente usados en una diversidad de dispositivos electroópticos, con lo que continuamente se está buscando mejorar sus propiedades. Mediante el dopaje de nanopartículas (NP) de diferente tamaño, forma o composición se pueden alcanzar mayores birrefringencias del cristal líquido, así como un cierto control sobre las resonancias de las nanopartículas, que aparecen en un amplio rango del espectro electromagnético.

En el presente trabajo se ha procedido a simular las propiedades ópticas del cristal líquido E7 cuando se dopa con nanopartículas esféricas metálicas y semiconductoras. Para los cálculos de la birrefringencia, se ha utilizado la Teoría de Índice Efectivo. Para las distintas simulaciones se han supuesto diferentes tamaños y cantidades de NP’s dopantes para un mismo tipo de CL.

Por su parte, para el estudio de las resonancias se ha usado la Teoría de Mie, considerando NP’s de diferentes tamaños y a distintas concentraciones. Todas las simulaciones se han efectuado con el programa de cálculo Matlab.

Ver póster 9

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Recording POLICRYPS structures inside Photonic Crystal Fibers

David Poudereux1, Domenico Alj2, Roberto Caputo2, Eva Otón1, Xabier Quintana1, Cesare Umeton2, José M. Otón2

1CEMDATIC, ETSI Telecomunicación, Universidad Politécnica de Madrid, Madrid, Spain 2Department of Physics and CNR - NANOTEC, University of Calabria, Rende, Italy

Corresponding author e-mail: d.poudereux@upm.es

Keywords (3): POLICRYPS, Liquid Crystal, Photonic Liquid Crystal

Abstract

The infiltration of photonic crystal fibers (PCF) with liquid crystals (LC) has greatly evolved since the first infiltration experiments. The combination of the passive properties of PCFs and the active optical properties of LCs has resulted in a new kind of versatile devices, the photonic liquid crystal fibers (PLCF). PLCFs have been developed and manufactured for many applications including optical communications, signal treatment, interferometers and sensors [1]. On the other hand, efforts have been paid to the development of electrically switchable holographic gratings in liquid crystalline composite materials. There are two main manufacturing procedures for recording these gratings, the holographic polymer-dispersed liquid crystal (H-PDLC) and its direct competitor POLICRYPS/POLYPHEMS gratings [2]. POLICRYPS gratings have been reported as alternative structures where no inhomogeneities are present. Recently an H-PDLC Bragg grating recorded inside all the holes of a PCF has been reported [3]. In the present work, a POLICRYPS structure has been recorded for the first time into selected holes of two different PCFs. The structure could become the basis of a new generation of electrically-controlled tunable fiber Bragg gratings.

Fig. 1. POLICRYPS in a hollow-core PCF.

The aim of the project has been to develop an electrically-tunable Bragg Grating in a PCF using an infiltrated POLICRYPS. For this purpose POLICRYPS were recorded inside the microholes of two PCFs, a Polarization Maintaining PCF and a Hollow Core PCF. The hole selected to be filled in the HC‐PCF was the hollow core. In the case of the PM-PCF, the selectively filled holes were the two wider holes near the solid core. With this particular distribution it becomes possible to switch between Total Internal Reflection and Band‐Gap waveguiding mechanisms.

Acknowledgements. Authors are grateful for financial support from Programa RETOS of the Spanish Ministerio de Economía y Competitividad, the regional R&D Program SINFOTON of the Comunidad de Madrid, and the EU COST Action IC1208.

References [1] D. Poudereux, P. Corredera, E. Otón, J. M. Otón and X.Q. Arregui, “Photonic liquid crystal fiber intermodal

interferometer,” Opt. Pura Apl. 46, 321–325 (2013). [2] R. Caputo, A.V. Sukhov, N.V. Tabirian, C. Umeton, and R.F. Ushakov, “Mass transfer processes induced by

inhomogeneous photo-polymerisation in a multicomponent medium,” Chem. Phys. 271, 323–335 (2001). [3] G. Zito, G. and S. Pissadakis, “Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core

photonic crystal fiber,” Opt. Lett. 38, 3253 (2013).

10 Ver póster

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Modulation Characteristics of a Three-Section Master Oscillator Power

Amplifier at 1.5 µm

Mariafernanda VILERA1, José Manuel G. TIJERO1, Pawel ADAMIEC2, Antonio PÉREZ-SERRANO1,

Mickael FAUGUERON3, Michel KRAKOWSKI3, Frederic VAN DIJK3, Ignacio ESQUIVIAS1

1CEMDATIC-E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid (UPM), 28040 Madrid, Spain. 2Alter Technology Tüv Nord S.A.U., 28760 Tres Cantos, Spain.

3III-V Lab. Thales Research & Technology. Campus Polytechnique 1, Avenue A. Fresnel, 91767 Palaiseau,

France. Corresponding author e-mail: mf.vilera@upm.es

Keywords: High brightness semiconductor lasers, direct modulation, master oscillator power

amplifier

Abstract

Direct optical modulation of a 1.55 µm three-section Master Oscillator Power Amplifier has been

demonstrated. The temporal response, the optical spectra and the optical modulation amplitude

have been analyzed as a function of the frequency and the modulating amplitude. For low

modulation amplitude, no spectral broadening was observed up to 1.5 GHz. However, at 12.5 MHz

an optical broadening of ~ 4 pm was observed for high modulation amplitudes. At this frequency

an extinction ratio of 40 dB has been achieved. The modulation amplitude degrades for frequency

values higher than 50 MHz. The device performance under modulation at 12.5 MHz is interesting for

its application as laser source for CO2 detection by differential absorption LIDAR operating in the

Continuous Wave Random Modulation mode.

Acknowledgements. This work has been supported by the European Commission through the

project BRITESPACE under grant agreement no. 313200. M. Vilera, J.M.G. Tijero, A. Pérez-Serrano,

and I. Esquivias also acknowledge support from the Ministerio de Economía y Competitividad of

Spain through project RANGER (TEC2012-38864-C03-02) and the Comunidad de Madrid under

program SINFOTON-CM (S2013/MIT-2790).

References

[1] I. Esquivias, et al, “High-brightness all semiconductor laser at 1.57 μm for space-borne LIDAR measurements of

atmospheric carbon dioxide: device design and analysis of requirements” Proc. SPIE 9135, Laser Sources and

Applications II, 913516 doi:10.1117/12.2052191 (2014).

[2] M. Faugeron, et al, “High Power Three-Section Integrated Master Oscillator Power Amplifier at 1.5 µm”, to appear in IEEE

Photon. Technol. Lett., 2015.

[3] M.W. Wright et al, “Temporal dynamics and facet coating requirements of monolithic MOPA semiconductor lasers,” IEEE

Photon. Technol. Lett. 10, 504-506 (1998).

[4] M. Spreemann, et al, “Measurement and Simulation of Distributted-feadback tapered master-oscillator power-

amplifiers,” IEEE J. Quantum Electron. 45, 609-616 (2009).

[5] M. Vilera, et al, “Emission characteristics of a 1.5 µm all semiconductor tapered master oscillator power amplifier”, IEEE

Photon. J. 7, 1500709, 2015.

[6] A. Pérez-Serrano, et al, “Wavelength Jumps and Multimode Instabilities in Integrated Master Oscillator Power Amplifiers at

1.5 µm: Experiments and Theory”, IEEE J. Sel. Topics Quantum Electron. 21, 1500909 (2015).

Ver póster 11

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Longitudinal Multimode Dynamics in Monolithically Integrated

Master Oscillator Power Amplifiers

A. Pérez-Serrano1, M. Vilera1, J. Javaloyes2, J.M.G. Tijero1, I. Esquivias1, S. Balle2,3 1CEMDATIC-E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid (UPM), E-28040 Madrid, Spain.

2Departament de Física, Universitat de les Illes Balears (UIB), E-07122 Palma de Mallorca, Spain. 3Institut Mediterrani d'Estudis Avançats, IMEDEA (CSIC-UIB), E-07190 Esporles, Spain.

Corresponding author e-mail: antonio.perez.serrano@upm.es

Keywords (3): Multi-section Semiconductor Lasers, Multimode Dynamics, Thermal Effects

Master Oscillator Power Amplifiers (MOPAs) are devices suitable for applications requiring high

brightness light sources. In addition, MOPAs are promising candidates to be modulated at high

speed, as required for applications such as LIDAR, free space optical communications and laser

projection displays [1]. Monolithically integrated MOPAs usually comprise two sections: an index

guided single lateral mode waveguide section that acts as a Master Oscillator (MO) (in our case a

Distributed Feedback laser (DFB)) and a gain-guided Power Amplifier (PA) section. Ideally, the

single lateral and longitudinal mode generated by the MO is injected into the PA section where it

undergoes free diffraction and amplification keeping its initial beam quality. However, MOPAs

often exhibit instabilities that have been attributed to a combination of thermal effects and the

residual reflectance at the amplifier front facet, which leads to coupling of the MO modes and the

modes of the full MOPA cavity [2].

In this contribution, we theoretically investigate the different dynamical regimes previously

observed in a MOPA emitting at 1.5 µm, in particular the jumps in emission wavelength of the

device from the Bragg wavelength to that of the gain peak [3]. The theoretical framework is a

Travelling Wave Model (TWM) [4] that naturally includes spatial effects (such as spatial hole burning

and coupled-cavity effects) and multimode dynamics. Thermal effects are included by considering

the optical response of the Quantum Well active medium within the quasi-equilibrium

approximation at finite temperature [5], with a phenomenological description of the redshift of the

gain peak and the changes in the background material refractive index by means of self- and

cross-heating coefficients for both sections [6].

Acknowledgements. This work has been supported by the Ministerio de Economía y

Competitividad of Spain through project RANGER (TEC2012-38864-C03-02 and TEC2012-38864-C03-

01). A. Pérez-Serrano, M. Vilera, J.M.G. Tijero and I. Esquivias also acknowledge support from the

European Commision through the project BRITESPACE under grant agreement no. 313200 and the

Comunidad de Madrid under program SINFOTON-CM (S2013/MIT-2790). A. Pérez-Serrano also

acknowledges support from the Ayudas Posdoctorales 2013 program. J. Javaloyes also

acknowledges support from the Ramon y Cajal fellowship.

References

[1] P. Adamiec, B. Bonilla, A. Consoli, J.M.G. Tijero, S. Aguilera, and I. Esquivias, “High-peak-power pulse generation from

monolithic master oscillator power amplifier at 1.5 µm”, Appl. Opt. 51, 7160 (2012).

[2] M. Spreemann, M. Lichtner, M. Radziunas, U. Bandelow, and H. Wenzel, “Measurement and simulation of distributed-

feedback tapered master-oscillator power amplifiers”, IEEE J. Quantum Electron. 45, 609 (2009).

[3] M. Vilera, A. Pérez-Serrano, J.M.G. Tijero, and I. Esquivias, “Emission characteristics of a 1.5 µm all semiconductor tapered

master oscillator power amplifier”, IEEE Photon. J. 7, 1500709 (2015).

[4] J. Javaloyes, and S. Balle, “Emission Directionality of Semiconductor Ring Lasers: A Traveling-Wave Description”, IEEE J.

Quantum Electron. 45, 431 (2009).

[5] J. Javaloyes, and S. Balle, “Detuning and thermal effects on the dynamics of passively mode-locked quantum-well

lasers”, IEEE J. Quantum Electron. 48, 1519 (2012).

[6] A. Pérez-Serrano, M. Vilera, J. Javaloyes, J.M.G. Tijero, I. Esquivias, and S. Balle, “Wavelength Jumps and Multimode

Instabilities in Integrated Master Oscillator Power Amplifiers at 1.5 μm: Experiments and Theory”, IEEE J. Sel. Topics Quantum

Electron. 21, 1500909 (2015).

12 Ver póster

Manufacturing arbitrarily-shaped active waveguides with liquid crystal cladding

Manuel Caño1*, Rodrigo Delgado1, Tianyi Zuo1, Morten A. Geday1, Xabier Quintana1, José M. Otón1 1 CEMDATIC, ETSI Telecomunicación, Universidad Politécnica de Madrid,

Av. Complutense 30, 28040 Madrid, Spain

*manuel.c@upm.es

Keywords (3): Waveguides manufacturing, micromaterials, electrooptic devices.

Abstract

Many photonic devices are based on waveguides (WG) whose optical properties can be externally modified. These active WGs are usually obtained with electrooptic materials in either the propagating film (core) or the substrate (cladding). In the second case, the WG tunability is based on the interaction of the active material with the evanescent field of the propagating beam. Liquid crystals (LCs) are an excellent choice as electrooptic active materials since they feature high birefringence, low switching voltage, and relatively simple manufacturing.

In this work, we have explored alternative ways to prepare WGs of arbitrary shapes avoiding photolithographic steps. To do this, we have employed a UV laser unit (Spectra Physics)attached to an xyzCNC system mounted on an optical bench. The laser power is 300mW, the spot size can be reduced slightly below 1 µm, and the electromechanical positioning is well below that number. Different photoresins have been evaluated for curing time and uniformity; the results have been compared to equivalent WGs realized by standard photolithographic procedures.

Best results have been obtained with several kinds of NOA adhesives (Norland Products Inc.) and SU8 (Microchem). NOA81 optical adhesive has been employed by several groups for the preparation of microchannels [1] and microfluidic systems[2]. In our case, several NOAs having different refractive indices have been tested in order to optimize light coupling and guiding

Figure 1: Selective curing of NOA81 with a355 nm laser. The segment widths increase with the number of sweeps done by the laser

Figure 1 shows several attempts to optimize the laser-induced waveguides. The adhesive is spinned onto a substrate, and a number of segmented WGs are written with the laser system. The laser power is attenuated 20 dB. Then the laser spot is swept a number of times (from 1 to 900) on every segment. It has been found that, for example, the optimum number of sweeps for NOA81 is 30-70 times (center of the figure) under these conditions. The WG dimensions obtained with this procedure are about 7 µm high and 12 µm wide.

Once the WGs have been prepared, a second substrate with ITO-coated surface is added up to make switchable LC cells. The performance of these optimized systems will be shown.

References [1] P. Wägli, A. Homsy, and N. F. de Rooij, “Norland optical adhesive (NOA81) microchannels with adjustable surface properties” Procedia Eng., 5, 460–463 (2010). [2] D. Andrews, “Photonics, Volume 2: Nanophotonic Structures and Materials” Wiley, Hoboken, USA (2015) p. 288.

Ver póster 13

Cloaking device based on a photonic crystal

Juan Luis Garcia-PomarInstituto de Óptica “Daza de Valdés”, Consejo Superior de Investigaciones Científicas (IO-CSIC). Madrid, Spain

Corresponding author e-mail: garciapomar@io.cfmac.csic.es

Keywords (3): cloaking, photonic crystal, self-collimation.

Abstract

In this communication I proposed a structure based on a self-collimated photonic crystal [1] in order to cover a wider range of angles of incidence, decreasing the uncloaking zone, and avoid the metallic losses from other devices [2]. For the realization of the structure I consider a 2D square photonic crystal lattice made of dielectric cylinders.

This photonic crystal has a dominant propagation along the ΓM direction due to the flat frequency equisurfaces. After penetrating, the beam is self-waveguided up to a tilted interface where it impinges at an angle of 45º perpendicular to the XM direction. In this interface all of the propagating wavevectors inside the photonic crystal do not provide a permitted propagating wavevector in the air-medium that satisfies the parallel component conservation. Due to the symmetry of the crystal, only incidence under Φ=45º provides this bending by total internal reflection.

The device is based in a truncated square form photonic crystal tilted 45º, where an internal square empty space is cloaked by multiple reflections.

As example (Fig.1) an incident Gaussian beam impinges from the bottom to the first interface of the photonic crystal propagating along the direction ΓM then occurs a total reflection in an internal square hole (where the object to be cloaked can be placed) after the first re-flection, a second and third reflections occur in the external tilted interface. Finally, another total reflection takes place in the upper part of the internal square hole, going out of the photonic crystal.

Fig. 1. Snapshot of the electric field Ez (arbitrary units) for the proposed cloaking device.

Acknowledgements. This work has been supported by the project TEC2012-37958-C02-02 and TEC2012-37958-C02-01 from Ministerio de Economía y Competitividad of Spain and by the project S2013/MIT-2790 (SINFOTON) from Comunidad Autónoma de Madrid. J.L. G-P. acknowledges European Social Fund (ESF) for partially supporting JAE-Doc program.

References [1] J.L. Garcia-Pomar and M. Nieto-Vesperinas “Imaging properties of photonic crystals” Optics Express 15, 7786-78010 (2007)[2] D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, and D. R. Smith, “Metamaterial electromagneticcloak at microwave frequencies,” Science 314, 977–980 (2006).

14 Ver póster

Evaluación de la homogeneidad de fuentes de estado sólido orgánicas (OLEDs)

J. L. Velázquez, A. Ferrero, A. Pons, J. Campos, M. L. Hernanz, E. Borreguero y B. Bernad Departamento de Imágenes, Visión e Instrumentación Óptica, Instituto de Óptica, CSIC, C/Serrano, 121 c. p.

28006, Madrid, España. Corresponding author e-mail: jl.velazquez@csic.es

Palabras clave (3): Campo Cercano, Gonioespectrofotómetro, Homogeneidad.

Resumen:

Los últimos avances en tecnología de iluminación han llevado a desarrollar y construir nuevas fuentes de radiación basadas en fuentes de estado sólido orgánicas (OLEDs). Este tema ha suscitado en nuestro laboratorio el desarrollo de un sistema de medida capaz de analizar la superficie de radiación de estas nuevas fuentes.

Para el estudio de estas fuentes el IO-CSIC ha diseñado y construido un Goniofotómetro de campo cercano [1] compuesto por dos motores paso a paso dispuestos perpendicularmente sobre un banco óptico. Los motores dotan al sistema de movimiento, de varios grados de libertad angulares. Estos grados de libertad permiten seleccionar diferentes direcciones de emisión de la fuente, que son registradas por el sistema de detección. El sistema de detección está compuesto por una cámara CCD de 12 bits con un objetivo de 50 mm que es capaz de medir la distribución espacial de luminancia [2] en distintos intervalos del espectro electromagnético. Estas medidas son posibles porque a la cámara CCD se le ha acoplado un filtro sintonizable que es sensible en un rango espectral comprendido entre los 400 nm y los 700 nm.

El estudio ha sido realizado en base a un conjunto formado por 10 OLEDs, de diferentes formas y tamaños (figura 1), fabricados por varias empresas. El procedimiento consiste en realizar un análisis de la distribución espacial de radiancia en cada una de las superficies. Esto permite examinar la homogeneidad de radiancia en la superficie debida a un cambio en el ángulo azimutal de observación. Las diferencias de homogeneidad serán también comprobadas en relación con la longitud de onda examinada.

Fig. 1. Distribución de luminancia de los OLEDs medidos en el Gonioespectrofotómetro del IO-CSIC.

Los resultados obtenidos por este procedimiento revelan la importancia de modificar el ángulo de visión así como la diferencia de homogeneidad colorimétrica cuando es observado en distintas geometrías.

Agradecimientos. Los autores agradecen al programa EMRP por el proyecto subvencionado ENG62 MESAIL “Metrology for efficient and safe innovative lighting”. Los autores también agradecen a la Comunidad de Madrid por subvencionar el proyecto SINFOTON-CM: S2013/MIT-2790.

Bibliografía [1] J. L. Velázquez, A. Ferrero, M. López, A. Pons, A. Villamarín, J. Campos, and A. Sperling, “Angular distribution of the averaged luminous intensity of low power leds transfer standards”. Proceeding SPIE, 8785:87858W–87858W–8 (2013). [2] A. Ferrero, M. López, J. Campos, and A. Sperling, “Spatial characterization of cameras for low-uncertainty radiometric measurements”, Metrologia, 51(3):316 (2014).

Ver póster 15

Construcción y caracterización de un dispositivo basado en sensores de temperatura para autocalibrado de fotodiodos

E. Borreguero1, C.K. Tang2, J. Gran2, A. Pons1, J. Campos1, M.L. Hernanz1, J.L. Velázquez1 and B. Bernad1

1Departamento Imágenes, Visión e Instrumentación Óptica, Instituto de Óptica-CSIC, Madrid, España 2 Radiometri Laboratorium, Justervesenet, Kjeller, Noruega

e-mail: elisa.borreguero@io.cfmac.csic.es

Palabras clave: fotodiodos, autocalibración, termistores.

Resumen

La calibración de fotodiodos se realiza determinando su responsividad, magnitud definida como el cociente entre la respuesta eléctrica y la potencia óptica incidente, frente a un patrón de flujo radiante. Este trabajo estudia la viabilidad para autocalibrar fotodiodos, a temperatura ambiente, determinando experimentalmente su responsividad mediante un único dispositivo que funciona en dos modos, como fotodetector y como radiómetro de sustitución eléctrica.

El dispositivo se construyó empleando un fotodiodo de silicio como detector y dos termistores, de coeficiente de temperatura negativa, como sensores de temperatura. Con él, se determina la responsividad del fotodiodo comparando su incremento de temperatura bajo iluminación con el producido por calentamiento eléctrico. La respuesta generada como fotodetector, la fotocorriente medida, es proporcional a la radiación óptica incidente. Por otro lado, si se emplea la radiometría de sustitución eléctrica para determinar la potencia óptica incidente, se conocerá la responsividad. La idea es calentar el fotodiodo, por efecto Joule con una polarización eléctrica directa [1], suministrando una potencia equivalente a la óptica incidente, cuyo valor se calcula estimando el incremento de temperatura debido a la absorción del flujo radiante por parte del material del fotodiodo.

El objetivo de esta comunicación es determinar el rango óptimo de trabajo de ambos modos. Midiendo la fotocorriente correspondiente a distintos niveles de potencia óptica, se encontró una relación lineal entre ambas magnitudes entre 300 µW y 1000 µW, figura 1, donde el calentamiento inducido en el fotodiodo de forma óptica y eléctrica puede considerarse equivalente.

Fig. 1. Correspondencia de las respuestas de los dos modos de funcionamiento del sistema bajo iluminación.

Este método haría posible predecir, experimental e independientemente, la responsividad de los nuevos radiómetros PQED [2, 3], que han demostrado su potencial para ser patrones primarios.

Agradecimientos. A la Comunidad de Madrid, por la financiación del proyecto S2013/MIT-2790-SINFOTON-CM, y EMRP, financiado conjuntamente por los países de EURAMET participantes y la Unión Europea, por la concesión de su ESRMG dentro del proyecto europeo JRP SIB57-NEWSTAR.

Referencias [1] M. White, J. Gran, N. Tomlin and J. Lehman, “A detector combining quantum and thermal primary radiometric standards in the same artefact”, Metrologia 51, 245-251 (2014) [2] M. Sildoja, F. Manoocheri, M. Merimaa, E. Ikonen, I. Müller, L. Werner, J. Gran, T. Kübarsepp, M. Smîd and M.L. Rastello, “Predictable quantum efficient detector: I. Photodiodes and predicted responsivity”, Metrologia 50, 385-394 (2013) [3] I. Müller, U. Johannsen, U. Linke, L. Socaciu-Siebert, M. Smîd, G. Porrovecchio, M. Sildoja, F. Manoocheri, E. Ikonen, J. Gran, T. Kübarsepp, G. Brida and L. Werner, “Predictable quantum efficient detector: II. Characterization and confirmed responsivity”, Metrologia 50, 395-401 (2013)

16 Ver póster

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Temperature drift compensation in high-resolution Fourier-transform micro-spectrometers

Aitor V. Velasco1*, Juan Galindo-Santos1, Pavel Cheben2, María L. Calvo3, Jens Schmid2, André Delâge2, Dan-Xia Xu2, Siegfried Janz2, Pedro Corredera1

1 Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain 2 National Research Council Canada, Ottawa, Ontario, Canada

3 Departamento de Óptica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Spain

*Corresponding author e-mail: a.villafranca@csic.es

Keywords: Fourier spectroscopy, Silicon on Insulator, temperature drift

Abstract

In this work, we analyze and compensate the effect of environmental changes during the operation of a spatial heterodyne Fourier-transform micro-spectrometer fabricated in a Silicon-on-insulator chip [1]. The device comprises an array of 32 Mach-Zehnder interferometers implemented with microphotonic spirals of linearly increasing length [2], as shown in Fig. 1. This configuration provides a resolution of 42 pm in a footprint under 12 mm2. However, this remarkable resolution comes at the cost of a greater sensitivity to temperature variations during the spectrometer operation. Fig. 2 showcases the effects of retrieving the spectrum of a monochromatic signal with several temperature mismatches between calibration and operation. Central frequency drifts and sidelobe artifacts are observed. To mitigate this issue, compensation techniques based on multiple calibration matrices are presented.

Fig. 1. Optical micrograph of the fabricated

spectrometer. Fig. 2. Spectral retrieval of a monochromatic signal as a

function of the temperature mismatch between calibration and operation.

Acknowledgements. This work was supported by the Spanish Ministry of Economy through projects TEC2012-37958-C02-02 and TEC2012-37958-C02-01, Community of Madrid through project S2013/MIT-2790, and EURAMET through project JRP-i22 IND22 Photind.

References

[1] A. V. Velasco, P. Cheben, M. Florjańczyk, M. L. Calvo, “Spatial heterodyne Fourier-transform waveguide spectrometers”, in Progress in Optics 59, Elsevier, Oxford, 2014. [2] A. V. Velasco, P. Cheben, P. J. Bock, A. Delage, J. H. Schmid, J. Lapointe, S. Janz, M. L. Calvo, D.-X. Xu, M. Florjańczyk, M. Vachon, “High-resolution Fourier-transform spectrometer chip with microphotonic silicon spiral waveguides”, Opt. Lett. 38, 706-708 (2013).

Ver póster 17

POF fiber coupler fabrication through chemical degradation with acetone

Conchi Pulido, Pedro Corredera and Juan Diego Ania Castañón Instituto de Óptica “Daza de Valdés”, CSIC, Madrid, Spain

Corresponding author e-mail: c.pulido@csic.es

Keywords (3): Polymer Optical Fibers, fiber-optic couplers, chemical degradation

Abstract

In spite of their higher attenuations and shorter operational temperature range, polymer optical fibers present a number of advantages in terms of low cost, easy handling and robustness that makes them particularly interesting for a range of applications in short-distance transmission and sensing. A critical component in many of these applications is the optical fiber coupler. In the case of POF, different technologies can be applied to the development of optical fiber couplers, including direct molding, side-polishing and fusing, fiber twisting, mixing rods, waveguide coupling, and wave front division, among others[1][2]. These methods present some limitations, such as undesired Fresnel reflections in the case of couplers with intermediate media, or the need for time-consuming processing, in the case of side polishing and fusing. Moreover, several sensing applications can benefit from a long interaction length between the evanescent fields of neighbouring fibers, which are not achievable through standard techniques. Here we present a fast and low-cost process to achieve coupling between two or more neighbouring fibers, based on the direct chemical degradation of the fiber surface with acetone.

Coupling and losses measured after each treatment are shown (for Raytela™ Toray Industries´ POF PGR-FB500 using a laser source at 632 nm). In the case of identical treatments for two fibers there is an increase in the coupling up to the 8th treatment. The losses increase abruptly up to the 2nd treatment and decrease afterwards, reaching a plateau close to the 8th treatment. This behavior can be related to the changes of surface morphology that take place after successive treatments. An example of this is shown in the second figure where we show the surface of the fiber after two and eight treatments. A diffuse scattering of the light is present after the first treatment, whereas identifiable scattering points are present after 8 treatments. Interestingly, and due to this noticeable variation in the scattering mechanism, the optimal number of treatments for maximum coupling does not coincide with that for maximum losses.

Fig. 1. Left: Coupling between two chemically degraded POFs. Right: Losses measured in one fiber after each treatment

Fig. 2. POF surface after two chemical treatments (left) and eight treatments (right)

Acknowledgements. This work was supported by MINECO through projects TEC2012-37958-C02-02, TEC2012-37958-C02-01 and TEC2011-27314, and CAM through project S2013/MIT-2790.

References [1] A. Annuar Ehsan et al., “Low cost 1x2 acrylic-based plastic optical fiber coupler with hollow taper waveguide”, PiersOnline, 5, 129-132 (2009)[2] K. Imoto et al. “Plastic optical fiber star coupler”, Applied optics, 25, 3443-3447, (1986)

18 Ver póster

Síntesis de referencias ópticas mediante filtrado Brillouin de un peine de frecuencias

Juan GALINDO-SANTOS(1), Aitor V. VELASCO(1), Ana CARRASCO-SANZ(2), y Pedro CORREDERA(1). 1Instituto de Óptica IO-CSIC, c/Serrano 121, 28006 Madrid

2Facultad de Ciencias, Universidad de Granada, Campus Universitario de Fuentenueva, 18071 Granada Persona de contacto: Juan Galindo-Santos (j.galindo@csic.es).

Keywords (3): Peine de frecuencias ópticas, Scattering estimulado Brillouin, Metrología

RESUMEN:

Los peines de frecuencias son trenes de pulsos ópticos periódicos generados por un láser en modo anclado (“mode-locked”), que en el dominio de la frecuencia resulta en una estructura compuesta por un gran número de líneas equi-espaciadas [1]. La gran estabilidad de los peines de frecuencia ha impulsado su aplicación a diversos campos de la ciencia y la tecnología, como la metrología, la espectroscopía o las comunicaciones ópticas. En este trabajo se propone un sistema para la generación de frecuencias ópticas basado en el filtrado mediante scattering Brillouin estimulado (SBS) [2] de un peine de frecuencias auto-referenciado. Este esquema permite ajustar de forma muy precisa la frecuencia a sintetizar dentro del espectro del OFC, alcanzándose una resolución de sintonización por debajo de los 20 Hz en la banda C de comunicaciones ópticas. El esquema ha sido demostrado experimentalmente utilizando como fuente de bombeo del SBS dos láseres distintos en banda C estabilizados en dos absorciones moleculares del acetileno 12C2H2. La caracterización de las frecuencias sintetizadas muestran una estabilidad por debajo de 4×10–11 para tiempos de medida de 1 s y una anchura de línea de 75 kHz. Esto supone una mejora respecto al bombeo de casi dos órdenes de magnitud en estabilidad y diez veces en ancho de línea. El análisis de la estabilidad a largo plazo demuestra que la señal sintetizada hereda las tendencias del bombeo, transmitidas a través del ruido de fase de la amplificación Brillouin, pero manteniendo el rango de mejora inicial.

Fig. 1. Desviación de Allan modificada del láser de bombeo Brillouin (línea discontinua), del modo óptico del OFC (negro) y

la frecuencia sintetizada (línea continua). Las curvas de color rojo y azul, corresponden con los láseres de bombeo anclados en las líneas P11 y P25 respectivamente.

Agradecimientos. Este trabajo ha sido financiado en parte por el Ministerio de Economía de España a través de los proyectos TEC2012-37958-C02-02 y TEC2012-37958-C02-01, la Comunidad de Madrid a través del proyecto S2013/MIT-2790, y EURAMET a través de los proyectos EMRP: JRP IND14 FREQUENCY y JRP-i22 IND22 Photind.

References [1] S. T. CUNDIFF, J. YE, “Femtosecond optical frequency comb technology”, (Springer, 2005). [2] G. P. AGRAWAL, “Nonlinear Fibre Optics”, (Academic Press, 2007).

Ver póster 19

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Nonlinear compensation with advanced Raman amplification and optical phase conjugation

Pawel Rosa1!, Giuseppe Rizzelli1, and Juan Diego Ania-Castañón1

11Instituto de Óptica, Consejo Superior de Investigaciones Cientificas, Madrid 28006, Spain !Corresponding author e-mail: p.g.rosa@icloud.com

Keywords (3): Optical phase conjugation, Raman amplification, Coherent communication

Abstract

The nonlinear-Shannon limit sets a cap to maximum capacity in single mode optical fibres [1]. To combat fibre nonlinear effects, using mid-link or transmitter-based optical phase conjugation (OPC) enables real time compensation of all deterministic (signal×signal) nonlinear impairments. However, the degree of nonlinear compensation using mid-link OPC is related to the symmetry match of the conjugated and transmitted signal power evolution in the fibre. Meaningful performance improvement has only been demonstrated in Raman-based amplification optical links [2], thanks to the better control over signal symmetry provided by distributed amplification, as well as its improved noise performance. The key to maximise performance in OPC-assisted systems, lies in reducing signal power asymmetry within the periodic spans while ensuring a low impact of noise and non-deterministic nonlinear impairments in the over- all transmission link.

Fig. 1. Schematic design of 1st order Raman (a), 2nd order URFL (b) and random DFB Raman laser amplifier (c).

In this letter, we demonstrate, using proven numerical models, that almost ideally symmetrical signal power evolution can be achieved in advanced distributed amplification schemes, with the best results obtained for half- open-cavity random distributed feedback (DFB) Raman laser amplifier with bidirectional 2nd order pumping. This setup allows to potentially reduce signal power evolution asymmetry inside the span with respect to its middle point to a mere 3% over a realistic span of length- 62 km SMF, which constitutes the highest level of symmetry achieved up to date on such a long span.

Fig. 1. Lowest signal power asymmetry for a given length and amplification setup. Insets show the corresponding best OSNR

(a) and the accumulated Residual Phase Shift (product of nonlinear phase shift and asymmetry)(b).

Acknowledgements. We acknowledge the MSC IF ‘CHAOS’, FP7 ITN ICONE, and MICINN RAMAS.

References

[1] A. D. Ellis, J. Zhao, and D. Cotter “Approaching the Non-Linear Shannon Limit,” J. Lightw. Technol. 28(4), (2010). [2] I.D.Phillips et al., “Exceeding the nonlinear Shannon limit using Raman fibre based amplification and optical phase conjugation,” in Proc. OFC, (2014), paper M3C.1.

FBG FBG

FBG

Raman Pump 1366 nm

Raman Pump 1455 nm

Raman Pump 1366 nm

Raman Pump 1455 nm

TX

TX

TX RX

RX

RX Raman Pump 1366 nm

Raman Pump 1366 nm

a)

b)

c)

20 Ver póster

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Single FBG, Open-Cavity Spun Fibre Raman Lasers with aPolarised Output

J. Nuño1, G. Rizzelli1, C. Pulido-De-Torres1, F. Gallazzi1, F. Prieto2, P. Corredera1, S. Wabnitz3, J. D. Ania-Castañón1

1.Instituto de Óptica “Daza de Valdés”, CSIC (IO-CSIC). C/ Serrano 121 28006 Madrid (Spain).

2.Saint Louis University - Madrid Campus, Avenida del Valle 34, 28003 Madrid (Spain).

3.Dipartimento di Ingegneria dell'Informazione, Università di Brescia, via Branze 38, 25123 Brescia (Italy).

Corresponding author e-mail: c.pulido@csic.es

Keywords (3): Optical Fibre, Raman scattering, Polarisation.

Abstract

Polarization dependent gain (PDG) and polarization mode dispersion (PMD) pose importantlimitations both to the performance of next-generation optical communication systems relying ondistributed amplification and to the design of low-noise fibre lasers. In this context, nonlinear effectshave been recently demonstrated as potential key technologies to develop polarisation controldevices. Some examples of this approach are the Raman polariser [1, 2] and the omnipolariser [3].

Here, we experimentally study the performance and behaviour of two open-cavity lasers basedon spun fibre with a Fibre Bragg Grating (FBG) a highly polarised 1366 nm pump. The schemes aredepicted in fig. 1(a). In both configurations, we observe a 1453 nm lasing signal co-propagatingwith the pump, corresponding to the maximum Raman Stokes peak. Fig. 1 (b) shows the outputspectrum for Scheme 2. The lasing wavelength does not correspond to that of the FBG, suggestingdistributed Rayleigh backscattering as the dominant mechanism on the co-propagatingcomponent. Parametric effects become dominant when the pump is not polarised, leading tosupercontinuum generation and, consequently no lasing is achieved in such case. The 1453 nmsignal is slightly polarized (The degree of polarisation, DOP, is between 65% and 95% for the Scheme1 and between 75% and 100% for the Scheme 2). The state of polarisation (SOP) of this signal movesalong the complete Poincaré sphere following the SOP of the pump.

Fig. 1. (a) Studied configurations. (b) Output spectrums for the scheme 2. (c) Poincaré sphere for the counter-propagatingsignal at 1454.5 nm with scheme 2.

At the other end of the fibre, we observe two peaks (see subplot in fig. 1 (b)). One weak peak issituated at 1453 nm due to Rayleigh backscattering and another peak is located at 1454.5 nm, theFBG wavelength. In this case (see fig. 1(c)) its polarisation is attracted to a small region of thePoincaré sphere with a DOP close to 100%.

Finally, the same setup has been explored for comparison using a 3 km SMF. Although losses arelower and the fiber core smaller, the laser threshold is similar to the spun fibre case, showcasing thereduced Raman gain efficiency of the SMF configuration. Most of the pump energy has been usedfor generating the supercontinuum at 1390 nm. As expected, repolarisation performance is worsefor all configurations based on SMF.

Acknowledgements. This work has been supported by the projects: TEC2011-27314, TEC2012-37958-C02-02, S2013/MIT-2790 (SINFOTON) and by the FP7-PEOPLE-2013-ITN 608099 (ICONE).

References

[1] M. Martinelli et al., Opt. Express 17, 947-955, 2009.[2] V. V. Kozlov et al., Opt. Lett. 35, 3970-3972, 2010.[3] J. Fatome et al., Scientific Reports 2, 938, 2012.

Ver póster 21

Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015. 23 de Octubre

Sputtered AlInN for sensing and photovoltaics

A. Núñez-Cascajero1, L. Monteagudo-Lerma1, S. Valdueza-Felip1, M. Jiménez-Rodríguez1,

Ó. Esteban1, M. González-Herráez1, F.B. Naranjo1 1Grupo de Ingeniería Fotónica, Departamento de Electrónica, Universidad de Alcalá, Ctra. Madrid-

Barcelona km. 33.6, 28871 Alcalá de Henares, Madrid, Spain Corresponding author e-mail: arantzazu.nunez@depeca.uah.es

Keywords (3): AlInN, sputtering, applications

Abstract

The high mechanical robustness and radiation hardness of III nitrides makes them interesting for

devices operating in harsh environments. In particular, the AlInN alloy offers the possibility of tuning

its refractive index and direct band gap energy by changing the Al content, both properties useful

for biosensing and photovoltaic applications. Moreover, the low cost sputtering technique allows

low temperature deposition enabling their integration with other material systems.

In this work, we investigate the use of AlInN layers with different compositions for biosensing and

photovoltaic applications. Particularly, for the use of AlInN as a biosensor we study the effect of:

sensor rotation during the ternary growth, the Al content of the dielectric overlay and the thickness

of metal layer on the SPR sensor properties. On thje other hand, for it use in photovoltaics we study

the influence of the deposition conditions (Al RF power, PAl, and deposition temperature, Tsubs) on

the structural and morphological properties of AlInN thin films deposited on p-doped Si(111)

substrates.

In the case of biosensing, the metallic (Al) and dielectric (AlInN) layers are grown over a uniform

waist tapered fiber using a reactive sputtering. The characterization of the developed Surface

Plasmon Resonance (SPR) sensors is based on the measurement of the spectral transmittance of

the device for different refractive indices of the outer medium. Sensors grown rotating the sample

are more homogenous leading to narrower peaks and higher sensitivities. The average sensitivity of

the devices calculated with the measured data increases when increasing the Al content of the

dielectric layer being 5780 nm/RIU, 7300 nm/RIU and 7600 nm/RIU for 0 %, 35 % and 100 %

respectively. Thus it is demonstrated the use of AlInN compounds as dielectric layers in SPR sensors.

If we focus on the effect of the metal layer thickness, when increasing it the sensitivity increases

although the peaks are wider.

In the case of photovoltaics, when increasing the PAl from 75 to 150 W and at Tsubs =300 °C, a

change in the morphology from closely packed columnar to compact is observed, with a two-fold

increase of the growth rate and a decrease of the RMS surface roughness from 6.7 to 3.1 nm.

Besides, the Al mole fraction linearly increases from 0.18 to 0.36 with PAl. On the contrary, the

compact structure, smooth surface morphology and Al content does not remarkably change

when varying Tsubs from 300 to 550 °C at a constant PAl of 150 W. The use of a buffer layer would

promote the film nucleation for improving the layer quality. Compact samples with 39 % of Al

content exhibit a strong photoluminescence (PL) emitting at 700 nm (1.77 eV) at low temperature.

The PL peak evolution from 5 to 300 K, shows a reduced redshift of 30 meV while keeping a high

luminescence efficiency, with an emission intensity decrease of only a factor of 1.6, which is

tentatively attributed to carrier localization. The layers present a residual carrier concentration in

the order of low-1020 cm-3, related to the presence of oxygen and carbon impurities

homogeneously distributed within the layer.

Acknowledgements: Partial financial support was provided by the Spanish Government projects

TEC2012 37958 C02 01 and TEC2014-58843-R, the Community of Madrid project S2013/MIT 2790, the

project CCG2014/EXP 051 and the FPI Grant from the Alcalá University and by the Marie Curie IEF

grant “SolarIn” (#331745).

22 Ver póster

Sputtered InN- and AlN-based optical waveguides for III-nitride all-optical integrated circuits at 1.55 µm

Laura Monteagudo-Lerma1, Arántzazu Núñez-Cascajero1, Sirona Valdueza-Felip1, Fernando B. Naranjo1, Marco Jiménez-Rodríguez1, Pablo A. Postigo2, Pedro Corredera3, and Miguel González-

Herráez1

1GRIFO, DEPECA, EPS, Universidad de Alcalá, 28871 Alcalá de Henares, Spain 2Instituto de Microelectrónica de Madrid, 28760 Tres Cantos, Madrid, Spain

3Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid, Spain Corresponding author e-mail: laura.monteagudo@depeca.uah.es

Keywords: III-nitrides, nonlinear optics, all-optical devices.

Abstract

Photonic integrated circuits (PICs) for working at the C-band of telecommunications require from active and passive all-optical devices. In a III-nitride technology, there are several approaches to cope with this specification. Among them, we demonstrated the nonlinear optical behavior of waveguides (WGs) based on GaN/AlN quantum heterostructures grown by molecular beam epitaxy, to operate as ultrafast saturable absorbers at 1.55 µm [1]. In the present work, we report the linear and nonlinear optical characterization of WGs based on InN [2] and AlN guiding layers deposited by the low-cost and thermally-harmless sputtering technique for ultrafast all-optical limitation and passive interconnection at 1.55 µm, respectively.

Compact- and columnar-InN guiding layers optimized for the fabrication of the WGs were

deposited by RF sputtering. These films present a RT direct optical band gap at ~1.7 eV (~730 nm), enabling a nonlinear two-photon absorption (TPA) process at 1.55 μm with a recovery time of 380 fs [3]. Optical design of the WGs was carried out by optical simulations using a commercial mode solver to obtain single mode propagation. The WGs were patterned by UV lithography and etched by sputtering. The nonlinear reverse saturable absorption effect at 1.55 µm was confirmed in both types of devices and for TE and TM polarizations of light. A nonlinear absorption coefficient as high as 114 cm/GW for TE-light is obtained, in agreement with values obtained for InN material [3], and larger than those of Si(111) and GaAs, being 0.88 and 10.2 cm/GW, respectively [4].

Passive WG interconnectors between active devices within III-nitride PICs can be implemented

by using AlN material, since it is transparent in the visible/near-infrared range. AlN WGs were based on optimized AlN layers deposited by RF sputtering following the two-step deposition method [5]. They were patterned by UV lithography and etched by reactive ion etching. These devices show a constant optical transmittance at 1.55 µm at linear and nonlinear regimes for both polarizations. Propagation losses of 7.1 dB/mm (TE-light) and 4.1 dB/mm (TM-light) were estimated via the cut-back method.

Acknowledgements. This work was supported by the Spanish Government project TEC2012-37958-C02-01 and the Comunidad de Madrid project S2013/MIT-2790.

References [1] L. Monteagudo-Lerma et al. Opt. Express 21(23), 27578 (2013). [2] L. Monteagudo-Lerma et al. IEEE Photon. Technol. Lett. 27(17), 1857 (2015). [3] S. Valdueza-Felip et al. IEEE Photon. Technol. Lett. 24(22), 1998 (2012). [4] M. Dinu et al. Appl. Phys. Lett. 82(18), 2954 (2003). [5] L. Monteagudo-Lerma et al. Thin Solid Films 545, 149 (2013).

Ver póster 23

Z-Scan measurements at 1.55 µm of saturable absorbers based on InN/InGaN MQWs grown by molecular beam epitaxy

M. Jiménez-Rodríguez1, S. Valdueza-Felip1,2,3, L. Monteagudo-Lerma1, A. Núñez-Cascajero1, E. Monroy2,3, S. Fernández4, P. Corredera5, M. González-Herráez1,

and F. B. Naranjo1 1University of Alcalá (GRIFO), Madrid-Barcelona Road km 33.6, 28871, Alcalá de Henares, Spain

2University Grenoble-Alpes, 38000 Grenoble, France 3CEA, INAC-SP2M, 17 av. des Martyrs, 38000 Grenoble, France

4CIEMAT, Avda. Complutense 22, 28040 Madrid, Spain 5Instituto de Óptica, CSIC, c/Serrano 144, 28006 Madrid, Spain

Corresponding author e-mail: marco.jimenez@depeca.uah.es

Keywords: III-nitride heterostructures, nonlinear optics, saturable absorbers.

Abstract

There is a recent growing demand from industry and research fields to develop pulsed lasers with short pulses and high power levels at telecommunication wavelengths to cover a broad range of applications. One common way to achieve this goal is taking advantage of the optical nonlinearity of saturable absorbers, to passively modulate the optical losses in a laser cavity [1]. InN-based structures grant these specifications due to their high thermal stability, high nonlinear optical response, and fast recovery time at 1.55 µm [2]. We report the nonlinear optical characterization of high In content InN/InGaN multiple-quantum wells (QW) through Z-Scan measurements at 1.55 µm.

The sample consists of 5-periods of InN/In0.9Ga0.1N (4.5 nm/7 nm) QWs grown by molecular beam

epitaxy on AlN on sapphire, designed to resonantly absorb at ~0.8 eV. A 110-nm-thick capping layer of GaN is grown to ensure the maximum overlapping of the electric field intensity with the active region. The nonlinear absorption coefficient, α2, and Kerr coefficient, n2, were estimated using open and close configurations for the Z-Scan technique, respectively [3]. The light source is a 280-fs-pulse laser with a 10 MHz repetition rate and an average power of 1.4 mW. A 3-cm-focal-length achromatic lens is used to focus the beam on the sample, leading to a beam waist of ω0 ~10 μm with a Rayleigh length of z0 ~500 μm and a maximum input optical power of 0.2 GW/cm2. Measurements in both configurations have been carried out leading to values of α2 ~ -4.2×104 cm/GW and n2 ~ 4.0 cm2/GW, estimated from the fitting of the Z-Scan experimental results to Sheik-Bahae equations [3].

Acknowledgements. This work was supported by the Spanish Government project TEC2012-37958-C02-01 and the Comunidad de Madrid project S2013/MIT-2790.

References [1] U. Keller, Nature. 424, 6950 (2003) [2] S. Valdueza-Felip et al., Appl. Phys. Lett. 101, 062109 (2012) [3] M. Sheik-Bahae et al., IEEE J. Quantum Electron. 26, 760 (1990)

24 Ver póster

Sensor BOTDA interferométrico basado en medidas distribuidas del desplazamiento de fase Brillouin

Alexia LOPEZ-GIL1, Xabier ANGULO-VINUESA1, Alejandro DOMINGUEZ-LOPEZ1, Sonia MARTIN-LOPEZ1, Miguel GONZALEZ-HERRAEZ1

1Departamento de Electrónica, Escuela Politécnica, Universidad de Alcalá, 28805, España Persona de contacto: alexia.lopez@uah.es

Palabras Clave (3): Scattering Brillouin, Sensor de fibra óptica distribuido, Interferometría

Resumen

En los últimos años, los sistemas de Análisis Óptico en el dominio del tiempo basado en Brillouin (BOTDA-Brillouin Optical Time Domain Analysis) [1], se ha convertido en una tecnología consolidada que se emplea para monitorizar temperatura y deformación sobre grandes distancias con resolución espacial del orden del metro.

El fenómeno físico en el que se basa un sensor BOTDA es el efecto óptico Scattering Brillouin estimulado (SBS-Stimulated Brillouin Scattering) [2]. Este efecto consiste en la transferencia de luz entre dos ondas contra-propagantes por medio de una onda acústica inducida. Por la naturaleza de esta onda, los fotones son dispersados sólo en una dirección, por tanto el SBS es un proceso no recíproco. El SBS se manifiesta como una curva de amplificación y una de atenuación contra-propagantes a la onda incidente, cuando una onda de luz de bombeo (ν0) intensa y coherente se introduce por el otro extremo de la fibra. El espectro de ganancia Brillouin (BGS-Brillouin Gain Spectrum) presenta una distribución de ganancia Lorentziana y tiene un perfil de fase Brillouin, conocido como espectro de desplazamiento de fase Brillouin (BPS-Brillouin Phase-shift Spectrum). Aunque los sistemas BOTDA miden normalmente las curvas de ganancia y atenuación del SBS, ya que estas se obtienen de la detección de forma directa, el BPS también puede ser usado para medir temperatura o deformación con una buena sensibilidad. Por ello, se ha demostrado que el BPS puede emplearse para realizar medidas dinámicas de vibraciones [3]. Además, también, se ha demostrado que este esquema es inmune a efectos no locales (agotamiento de bombeo) [4].

En este trabajo, proponemos una técnica BOTDA sencilla y novedosa que mide cambios de temperatura a partir de la medida del BPS distribuido beneficiándose de la sensibilidad de un Interferómetro de Sagnac (SI-Sagnac Interferometer) [5,6] a efectos no recíprocos. Este método simplifica los ya existentes para obtener medidas de BPS ya que no se necesita realizar modulación de fase ni emplear un detector de alto ancho de banda.

Agradecimientos. Este trabajo ha sido financiado en parte por el Ministerio de Ciencia i Innovación a través de los proyectos TEC2012-37958-C02-01, TEC2012-37958-C02-02 y TEC2013-45265-R, por la Comunidad de Madrid a través de los proyectos FACTOTEM2, SINFOTOM CM: S2013/MIT-2790, por el programa INTERREG SUDUE ECOAL-MGT, por el Consejo Europeo de Investigación a través de la Starting Grant U-FINE (Grant no. 307441) y EU-FP7 ITN ICONE. Sonia Martín-López le agradece al Ministerio de Economía y Competitividad a través de un contrato “Ramón y Cajal”.

Referencias [1] T.Horiguchi, and M.Tatela, “BOTDA-nondestructive measurements of single-mode optical fiber attenuation characteristics using Brillouin interaction: theory”, J. Lightwave Technol. 07, 1170-1176 (1989) [2] G. P. Agrawal, “Nonlinear Fiber optics”, Academic (2007) [3] J. Urricelqui, A. Zornoza, M. Sagües, A. Loayssa,”Dynamic BOTDA measurements based on Brillouin phase-shift and RF demodulation”, Opt. Express. 20, 26942-26949 (2012) [4] J. Urricelqui, M. Sagües, A. Loayssa,”BOTDA measurements tolerant to non-local effects by using a phase-modulated probe wave and RF demodulation”, Opt. Express. 21, 17186-17194 (2013) [5] B. H. Lee, Y.H. Kim, K.S. Park, J. B. Eom, M. J. Kim, B.S. Rho, H.Y. Chol., “Interferometric Fiber Optic Sensors”, Sensors 12, 2467-2486 (2012) [6] B. Culshaw, “The optical fibre Sagnac interferometer: an overview of its principles and applications”, Meas. Sci. Technol 17, R1-R16 (2006)

Ver póster 25

Efectos no locales en sistemas BOTDA con señal de sonda modulada en doble banda lateral

Alejandro Dominguez-Lopez, Xabier Angulo-Vinuesa, Alexia Lopez-Gil, Sonia Martin-Lopez y Miguel Gonzalez-Herraez

Departamento de Electrónica, Universidad de Alcalá, Alcalá de Henares, España E-mail: alejandro.dominguezl@uah.es

Palabras clave(3): Scattering Brillouin, óptica no lineal, sensores de fibra óptica.

Resumen

Las prestaciones de los sistemas basados en el análisis en el dominio del tiempo del scattering Brillouin (BOTDA, Brillouin Optical Time Domain Analysis) se han visto tradicionalmente limitadas por la aparición de efectos no locales en los mismos. De acuerdo con modelos recientemente propuestos [1], el uso de modulación de doble banda lateral (DSB, Dual sideband modulation) en la señal de sonda, mitiga eficazmente dichos efectos no locales, haciéndolos prácticamente despreciables, siempre y cuando la potencia de la señal de sonda no sobrepase el umbral del scattering Brillouin estimulado (SBS, Stimulated Brillouin Scattering). Sin bien dicha suposición es correcta en la mayoría de los casos, no consigue dar una explicación completa de los efectos no locales en la situación estudiada en el presente trabajo. En este trabajo mostramos la aparición de efectos no locales incluso para potencias de sonda notablemente inferiores al umbral SBS. Se ha observado que el espectro del pulso de bombeo se ve deformado y espectralmente desplazado dependiendo de la frecuencia de la modulación de la sonda [Fig. 1(a)], lo cual afecta a las curvas de ganancia y atenuación Brillouin recuperadas, principalmente hacia el tramo final de la fibra. Dicho fenómeno se intensifica cuando aumentamos la potencia de la señal de sonda. Asimismo, hemos comprobado que las medidas obtenidas en configuración de ganancia Brillouin son consistentemente más robustas a dichos efectos no locales que las de atenuación [Fig. 1(b-d)]. Del mismo modo, prevemos que dicha distorsión del espectro del pulso de bombeo acarreará severas consecuencias para la resolución espacial del sistema Creemos que todos estos resultados son de especial interés para desarrolladores de sistemas BOTDA de largo alcance.

Fig. 1: Resultados obtenidos para ~50 km de fibra SMF. a) Espectros eléctricos (75 kHz de Res. BW) del pulso de bombeo a la salida de la fibra, (Psonda ~500 μW en cada banda lateral), para distintas frecuencias de modulación de la señal de sonda. b) Evolución teórica y experimental de la anchura FWHM de los perfiles de ganancia y atenuación Brillouin a lo largo de la fibra. c) Representación teórica y experimental de las curvas de ganancia y atenuación Brillouin en el km 49.768 de la fibra. d) Evolución del desplazamiento Brillouin en frecuencia (BFS) para distintas potencias de sonda.

Agradecimientos: El presente trabajo ha sido financiado, en parte por el Consejo Europeo de Investigación a través del proyecto U-FINE (Grant 307441); a su vez por el Ministerio de Ciencia e Innovación a través de los proyectos TEC2012-37958-C02-01, TEC2012-37958-C02-02 and TEC2013-45265-R; el programa INTERREG SUDOE – ECOAL-MGT; y en parte por la Comunidad de Madrid bajo los proyectos EDISON (CCG2014/EXP-072) y SINFOTON-CM:S2013/MIT-2790. El trabajo de Sonia Martín López está avalado por el Ministerio de Economía y Competitividad a través de un contrato “Ramón y Cajal”.

Referencias [1] L. Thévenaz,S. F. Mafang y J. Lin, “Effect of pulse depletion in a Brillouin optical time-domain analysis system” Opt. Express 21(12), 14017-14035 (2013)

10.80 10.84 10.88 10.92 10.960.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50

10.868

10.870

10.872

0 10 20 30 40 50

10.868

10.870

10.872

0 10 20 30 40 50

10.868

10.870

10.872

0 10 20 30 40 5025

30

35

40

45

50

55

10.48 10.49 10.50 10.51 10.52

-88

-86

-84

-82

-80

d)c)b)

Gai

n (%

)

Frequency (GHz)

Gain - Exp. Gain - Theor. Loss - Exp. Loss - Theor.

275 µW 500 µW

Gain

a)

Loss

275 µW 500 µW

Freq

uenc

y (G

Hz)

500 µW

Gain Loss

Distance (km)

Wid

th (M

Hz)

Distance (km)

Gain - Exp. Loss - Exp. Gain - Theor. Loss - Theor.

Pow

er (d

B)

Frequency (GHz)

νB-10 MHz νB-15 MHz νB

νB+10 MHz νB+15 MHz

26 Ver póster

Estudio y caracterización de la dispersión cromática y SPM inducida en flujos de datos NRZ empleando técnicas PROUD

Juan Pastor-Graells1, Hugo F. Martins2, Luis Romero Cortés3, Daniel Piote2, Sonia Martin-Lopez1, José Azaña3, y Miguel Gonzalez-Herraez1

1Dep. Electrónica, Universidad de Alcalá, Alcalá de Henares, España 2FOCUS S.L., C/ Orellana, 1, 1º izquierda, 28004, Madrid, España

3Institut National de la Recherche Scientifique (INRS-EMT), Québec, Canada Corresponding author e-mail: juan.pastor@depeca.uah.es

Palabras clave (3): Recuperación de fase, fibra óptica, PROUD

Resumen

En este artículo se ha caracterizado en tiempo real la dispersión cromática y SPM inducida [1] en señales ópticas NRZ de 10 Gbps transmitidas a través de fibra óptica mediante un método en línea y sencillo.

Dicho método se basa en técnicas de reconstrucción de fase empleando diferenciación óptica ultrarrápida (PROUD) [2,3], una técnica lineal y autoreferenciada que no requiere de un oscilador local y su esquema de detección puede ser implementado con componentes estándar de comunicaciones ópticas y es completamente compatible con las redes ópticas convencionales.

En la Fig. 1 se observa la distorsión que sufre un pulso cuadrado al ser transmitido por una fibra óptica, tanto en amplitud como en fase. Variando la duración de dichos pulso, su potencia y la longitud de fibra que recorre, se ha podido caracterizar las situaciones en las que predomina la SPM o la dispersión cromática. A partir de las medidas experimentales, han podido ser estimados los coeficientes GVD (β2≈-20 ps2km-1) y no lineal (γ≈1.4 W-1km-1) de la fibra, ajustándose a los valores esperados [1].

-140 0 1400,0

0,2

0,4

0,6

0,8

1,0a)

FWHM=470ps

Pote

ncia

Ópt

ica

(ref.

a P 0)

tiempo (ps)

P0

10Km 8dBm 10Km 14dBm 50Km 8dBm 50Km 14dBm

-140 0 140-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

0,1 b) L=50km

Fase

(rad

)

tiempo (ps)

14dBm 12dBm 10dBm 8dBm 6dBm

-140 0 140-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0 c) P=14dBm

Fase

(rad

)

tiempo (ps)

10km 25km 50km

-140 0 140-0,09

-0,06

-0,03

0,00

0,03

0,06 d) P=8dBm

Fase

(rad

)

tiempo (ps)

10km 25km 50km

-60 -30 0 30 600,0

0,2

0,4

0,6

0,8

1,0 e) L=10km

Pote

ncia

Ópt

ica

(ref.

a P 0)

tiempo (ps)

P0

14dBm 12dBm 10dBm 8dBm 6dBm

FWHM=70ps

-60 -30 0 30 60-0,12

-0,08

-0,04

0,00

0,04 f) L=10kmFa

se (r

ad)

tiempo (ps)

14dBm 12dBm 10dBm 8dBm 6dBm

Fig. 1. Resultados experimentales. (a-d) 5 bits “1” en una secuencia de flujo de datos NRZ de 10 Gbps (Pulso cuadrado con una FWHM de 470 ps) (a) perfil de potencia, y perfil de fase para (b) variando la potencia de pico de entrada tras 50 km, (c) potencia de pico de entrada de 14 dBm tras 10/25/50 km (d) potencia de pico de entrada de 8 dBm tras 10/25/50 km. (e-f) “1” único en un flujo de datos NRZ a 10 Gbps (Pulso Gaussiano con una FWHM de 70 ps) (e) potencia y (f) perfil de fase bajo diferentes potencias de pico de entrada tras 10 km.

Agradecimientos. El trabajo ha sido apoyado en parte por fondos del Consejo Europeo de Investigación a través de Starting Grant UFINE (Grant no. 307441), EU-FP7 ITN ICONE, Plan Nacional de I+d+i” a través de los proyectos TEC2012-37958-C02-01, TEC2012-37958-C02-02, TEC2011-27314, TEC2013-45265-R, TIN2013-47630-C2-1-R, el programa regional SINFOTONCM: S2013/MIT-2790 financiado por la Comunidad de Madrid y el programa INTERREG SUDOE ECOAL-MGT. El trabajo de Sonia Martin-Lopez ha sido financiado por el Ministerio de Economía y Competitividad a través de un contrato “Ramón y Cajal”. El trabajo de Juan Pastor-Graells ha sido financiado por el Ministerio de Economía y Competitividad a través de un contrato FPI.

Referencias [1] Govind P. Agrawall, “Nonlinear Fiber Optics”, (2002) [2] Hamed P. Bazargani, Jean-Baptiste Quélène, Patrick Dumais, Antonio Malacarne, Matteo Clerici, Roberto Morandotty, Claire L. Callender, y José Azaña, “On-Chip, Single-Shot Characterization of Ghz-Rate Complex Optical Signals,” Photon. Technol. Lett. 26, 2345-2348 (2014) [3] José Azaña, Yongwoo Park, y Fangxin Li, “Linear self-referenced complex-field characterization of fast optical signals using photonic differentiation,” Optics Communications 284, 3772-3784 (2011)

Ver póster 27

Determinación simultánea de los perfiles de ganancia y fase en un BOTDA interferométrico

Xabier Angulo-Vinuesa1, Alexia Lopez-Gil1, Alejandro Dominguez-Lopez1, Jose L. Cruz2, Miguel V. Andres2, Sonia Martin-Lopez1, y Miguel Gonzalez-Herraez1

1aDepartamento de Electrónica, Universidad de Alcalá, C. Universitario, 28805, Alcalá de Henares 2Departamento de Física Aplicada, ICMUV, Universidad de Valencia, 46100, Burjassot

e-mail de contacto: xabier.angulo@uah.es

Palabras clave: scattering Brillouin, sensor distribuido de fibra óptica, interferometría

Resumen

Hasta ahora, las medidas complejas (intensidad y fase) en sistemas BOTDA (Brillouin Optical Time Domain Analysis) [1] requerían de complejos métodos de modulación de fase y de detección de alto ancho de banda (decenas de GHz) [2]. En este trabajo, proponemos una novedosa técnica que es capaz de obtener simultáneamente los perfiles de ganancia/atenuación y fase de la interacción Brillouin con tan sólo introducir un Interferómetro Sagnac (SI - Sagnac Interferometer) [3] en un esquema de sensado Brillouin estándar (ver Fig. 1a). A través del uso del SI es posible aprovechar la no-reciprocidad natural del sistema, por lo que la intensidad de la señal detectada será la combinación de la ganancia o atenuación junto con la diferencia de fase entre las señales que viajan en sentido contra-propagante dentro del SI. Realizando un filtrado adecuado y combinando linealmente las señales obtenidas, es posible obtener reconstruir los perfiles de ganancia/atenuación y sus respectivas fases, tal y como se muestra en la Fig. 1b para el caso particular de la ganancia Brillouin.

(a) (b)

Fig. 1. (a) Esquema de sensado SI-BOTDA. (b) Ganancia y fase Brillouin obtenidas al sumar y restar las señales medidas.

Además de ser capaz de obtener el perfil de fase con componentes BOTDA estándar, el sistema es capaz de realizar medidas redundantes de temperatura y/o deformación, lo que incrementa la eficiencia del sistema. Además, esta metodología abre la puerta a aprovechar la forma lineal del perfil de fase en la región del BFS para una determinación más efectiva de posibles inhomogeneidades.

Agradecimientos. Este trabajo ha sido financiado por el ERC a través de la Starting Grant U-FINE (307441), el Plan Nacional de I+D+i a través de los proyectos TEC2012-37958-C02-01/02 y TEC2013-45265-R, el programa INTERREG SUDOE con el pro-yecto ECOAL-MGT y la Comunidad de Madrid a través de los proyectos EDISON y SINFOTON. S. Martin-Lopez agradece el apoyo del Ministerio de Economía y Competitividad a través de un contrato “Ramón y Cajal”. J. L. Cruz y M. V. Andrés agradecen el apoyo económico del Ministerio de Economía y Competitividad y los fondos FEDER (proyecto TEC2013-46643-C2-1-R), y la Generalitat Valenciana (proyecto PROMETEOII/2014/072).

Referencias [1] T. Horiguchi, and M. Tateda, “BOTDA - Nondestructive measurement of single-mode optical fiber attenuation characteristics using Brillouin interaction: Theory,” IEEE J. Lightwave Technol. 7, 1170-1176 (1989) [2] A. Zornoza, M. Sagües, and A. Loayssa, “Self-heterodyne detection for SNR improvement and distributed phase-shift measurements in BOTDA,” IEEE J. Lightwave Technol. 30, 1066-1072 (2012) [3] B. H. Lee, Y. H. Kim, K. S. Park, J. B. Eom, M. J. Kim, B. S. Rho, and H. Y. Choi, “Interferometric fiber optic sensors,” Sensors 12, 2467-2486 (2012)

28 Ver póster

Viabilidad del empleo de sensores para radiación gamma basados en fibra óptica de plástico

Ana I. DE ANDRÉS1, Óscar ESTEBAN1, Miguel EMBID2

1Grupo de Ingeniería Fotónica de la UAH (GRIFO), Departamento de Electrónica, Escuela Politécnica

Superior, Universidad de Alcalá, Campus Universitario 28871 Alcalá de Henares, Madrid 2Laboratorio de Metrología de Radiaciones Ionizantes (LMRI), CIEMAT, Avda. Complutense 40, 28040

Madrid Persona de contacto: a_andres@depeca.uah.es

Palabras clave: Fibra íptica de plástico, radiación gamma, GADOX Resumen

En este trabajo, se ha desarrollado y medido un sensor para Rγ basado en fibra óptica de polímero sobre la que se deposita un medio centelleador. El material empleado es un Óxido de Gadolinio, comercialmente conocido como GADOX, dopado con Europio (Gd2O2S:Eu). El comportamiento de este material bajo irradiación [1,2,3], unido a su emisión a una longitud de onda de 625nm, lo hacen especialmente atractivo para su uso con detectores optoelectrónicos convencionales de silicio. El detector ha sido irradiado con una fuente de 137Cs, con dosis de Kerma de 2.5 Gy/h a una distancia de 0.915m.

El esquema básico de los sensores incluye el medio centelleador en formato polvo

rodeando a una fibra óptica estrechada, tal y como se muestra en la Fig. 1. GADOX polvo

POF estrechada

pintura reflectante

recubrimiento opaco

resina epoxy

Fig. 1. Esquema detector fabricado. Fig. 2. Espectro registrado para las muestras C1 (a) y C3 (b) Se han evaluado dos configuraciones de cabezal sensor diferentes. La muestra C1 de 1.5 cm de longitud de fibra estrechada, y la muestra C3 de 3cm de longitud sin estrechar. En la fig. 2, se pueden ver los resultados obtenidos, medidos en un espectrómetro. Si se comparan los dos espectros obtenidos puede observarse cómo el pico principal de emisión localizado a 625nm es ligeramente superior en el caso de C1, a pesar de que la longitud recubierta es la mitad. Se observa además un pico secundario a 545nm con una mayor intensidad en el segundo caso (C3) que en el primero (C1), lo que apunta a la influencia del método de fabricación y la configuración geométrica del cabezal sensor sobre la respuesta del mismo. Agradecimientos: Este trabajo ha sido parcialmente financiado por el programa SINFOTON de la Comunidad de Madrid, ref. S2013/MIT-2790 y el Laboratorio de metrología de radiaciones ionizante (LMRI) del CIEMAT. Referencias: [1] Bongsoo LEE, Young Mook HWANG, Hyo Sung CHO, Sin KIM, Seunghyun CHO. “Fabrication of fiber-optic radiation

sensor tips with inorganic scintillator for remote sensing of X or γ – ray” Nuclear Science Symposium Coneference Record, IEEE, Vol 2, 865-968 ,0-7803-8700-7/04/ 2004.

[2] Denis MCCARTHY, Sinead O’KEEFFE, G. LEEN, E. LEWIS. “Optical Fibre Radiation Dosimetry for Low Dose Applications”. IEEE SENSORS 2010 Conference. 978-1-4244-8168-2/10, 2010.

[3] Christos MICHAIL, George FOUNTOS, Panagiotis LIAPARINOS, Nektarios KALYVAS, Ioannis VALAIS, Ioannis KANDARAKIS, George PANAYIOTAKIS. “Light emission efficiency and imaging performance of Gd2O2S:Eu poder scintillator under x-ray radiography conditions”.Med. Phys. 37 (7), 2010.

400 450 500 550 600 650 700 750 8000

0.5

1

1.5

2

x 104

λ (nm)

Inte

nsid

ad (

u.a)

400 450 500 550 600 650 700 750 8000

0.5

1

1.5

2

x 104

λ (nm)

Inte

nsid

ad (

u.a)

(a) (b)

Ver póster 29

Tuning the In content in InGaN homojunctions synthesized by plasma-assisted molecular beam epitaxy

S. Valdueza-Felip1,2,3, , L. Redaelli1,2, A. Ajay1,2, Q. Li4, M. P. Chauvat4, P. Ruterana4, T. Cremel1,2, K. Kheng1,2, and E. Monroy1,2

1 University Grenoble-Alpes, 38000 Grenoble, France 2 CEA, INAC-SP2M, 17 av. des Martyrs, 38000 Grenoble, France

3 University of Alcalá (GRIFO), Mdr-Bcn Road, km 33.6, 28871 Alcalá de Henares, Spain 4 CIMAP, CNRS-ENSICAEN-CEA-UCBN, 6 Blvd. Maréchal Juin, 14050 Caen, France

Corresponding author e-mail: sirona.valduezafelip@uah.es

Keywords (3): InGaN, molecular beam epitaxy, solar cells

Abstract

InGaN junctions with 30% In have been proposed as a potential candidate for efficient double-junction solar cells, in combination with a Si junction. For such high In mole fractions, plasma-assisted molecular beam epitaxy emerges as a suitable technique for the growth of InGaN. We have recently reported on the interplay between In incorporation and strain relaxation in thick In0.3Ga0.7N layers on GaN-on-sapphire [1], with thickness and composition of the alloy depending not only on the growth conditions, but also on the strain state imposed by the underlayers.

Regarding the p-doping of the InGaN upper layer, we have explored Mg incorporation in In0.3Ga0.7N grown on insulating GaN:Fe-on-sapphire. The evaluation of the doping levels by Hall Effect measurements confirms a p-type conductivity with a hole concentration of 3.2×1018 cm-3 for low Mg fluxes (Mg cell temperature TMg ~ 250°C). As shown by transmission electron microscopy, the structural quality of the layers improves significantly with the Mg incorporation, since the density of stacking faults and dislocations decreases. However, an inversion of polarity from metal-polar to nitrogen-polar and an inversion of doping type from p to n occur for high Mg levels (TMg > 300°C).

P-i-n InGaN homojunctions were grown with different In contents (~10−40%). Higher In mole fraction (lower growth temperature) requires reducing the Mg flux to achieve efficient p-type doping. Secondary ion mass spectroscopy points to an increasingly (decreasingly) gradient of In (Ga) incorporation along the growth due to the already observed gradual relaxation, and verifies that the homogenously-distributed presence of Mg is not inhibiting this In incorporation. Mg concentrations of 6–15×1018 cm-3 were obtained.

Samples were processed into solar cell with mesa sizes of 0.5×0.5 and 1×1 mm2, and contacted a double p-layer based on Ni/Au, and n-contact (Ti/Al/Ni/Au) [2]. All junctions show rectifying current density vs. voltage behavior. The devices present a flat spectral response in the blue-green spectral region with a sharp cut-off which redshifts from 465 nm (blue) to 595 nm (orange), consistent with the In content of the samples. The photocurrent spectra correlate to the absorption band edge, as expected from the band diagram alignment. The spectral shift of the devices within one sample is in the range of 5−25 nm; this variation is attributed to the In content inhomogeneity on the wafer. The peak responsivity (external quantum efficiency) is 65.6 mA/W (17%) at 480 nm, 57.6 mA/W (14%) at 510 nm and 49.6 mA/W (12%) at 525 nm for samples with an indium mole fraction x~0.20, 0.30 and 0.35 (±0.01), respectively [3].

Acknowledgements. Partial financial support was provided by the Marie Curie IEF grant “SolarIn” (#331745), and by the French National Research Agency via the GANEX program (ANR-11-LABX-0014).

References [1] S. Valdueza-Felip et al. J. Appl. Phys 116, 233504 (2014) [2] S. Valdueza-Felip et al. Appl. Phys. Express 7, 032301(2014) [3] S. Valdueza-Felip et al. Submitted to Appl. Phys. Exp. (2015)

Fig. 1. External quantum efficiency spectral dependence of InGaN homojunctions with different In contents. Inset: device optical microscope top view.

30 Ver póster

Degradation of organic solar cells characterized by Impedance Spectroscopy

G. del Pozo1, B. Arredondo1, G. Susanna2, F. Brunetti2, and B. Romero1

1 Dpto. Tecnología Electrónica, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, C\ Tulipán s\n, 28933, Móstoles, Madrid, Spain

2 CHOSE (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, via del Politecnico 1, 00133 Rome, Italy

Keywords: Organic solar cells, impedance spectroscopy

Abstract

Organic solar cells have experimented a great improvement in terms of efficiency in the last decade [1]. Nevertheless, in order to make this technology ready for its commercialization, device lifetime has to be increased. The main cause of short lifetime is the degradation of the organic materials in presence of air and humidity. Impedance spectroscopy (IS) is a powerful technique that gives information about the dynamic processes that take place inside the active layer and at the different interfaces of the device [2], and thus it can be useful to understand the degradation processes occurring in the device. In this work the degradation of organic solar cells has been characterized by means of IS. The solar cells were based on a blend of the polymer PTB7 and the fullerene PC70BM. Using these materials we have fabricated devices with efficiencies around 9%, according to the state of the art reported values [3].

The use of an electric circuit is crucial to analyze the IS measurements. In this work we have used the circuit of Fig 1, similar to that proposed by Guerrero et al. [4], but including an inductance in series with the RS and the main circuit. The evolution of the circuit parameters has been studied in order to understand the physical processes involved in device degradation.

Figure 1. Electric Circuit used to simulate the OSC behavior.

Reference

[1] M. A. Green, K. Emery, Y. Hishikawa, W. Warta and E. D. Dunlop, “Solar cell efficiency tables (version 46)”, Progress in Photovoltaics: Research and Applications 23, (7), 805-812 (2015). [2] G. García-Belmonte, P.P. Boix, J. Bisquert, M. Sesolo, H.J. Bolink, “Simultaneous determination of carrier lifetime and electron density-of-states in P3HT:PCBM organic solar cells under illumination by impedance spectroscopy”, Sol. Energy Mater. Sol. Cells 94, 366–375 (2010). [3] Z. He, C. Zhong, S. Su, M. Xu, H. Wu, Y. Cao, “Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure”, Nat. Photon. 6 591–595 (2012). [4]A. Guerrero, T. Ripolles-Sanchis, P. P. Boix, and G. Garcia-Belmonte, “Series resistance in organic bulk-heterojunction solar devices: Modulating carrier transport with fullerene electron traps”. Organic Electronics, 13(11), 2326–2332 (2012).

Ver póster 31

Gonio-fluorescencia de patrones luminiscentes B. Bernad1, A. Ferrero1, J. L. Velázquez1, A. Pons1, M.L. Hernanz1, E. Chorro2, E. Perales2, F.M.

Martínez-Verdú2, E. Borreguero1 y J. Campos1 1Instituto de Óptica, Agencia Estatal Consejo Superior de Investigaciones Científicas, Madrid, Spain

2Dpto de Óptica, Farmacología y Anatomía, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain berta.bernad@csic.es

Palabras clave (3): goniofluorescencia, BRDF, luminiscente.

Resumen

El objetivo de este trabajo es la medida de la variación del espectro de excitación de la fluorescencia, en función de las direcciones de irradiación y detección, lo que puede ser denominado como “goniofluorescencia”. Para ello, se ha medido la función de distribución de la luminiscencia bidireccional (BLDF) de cinco patrones de fluorescencia de diferentes colores Spectralon a diferentes geometrías.

Estas medidas se han realizado con el gonioespectrofotómetro GEFE, un dispositivo desarrollado en el IO-CSIC para la medida de la función de distribución del scattering bidireccional (BSDF) a cualquier geometría. Se utilizó iluminación monocromática y un espectrorradiómetro como detector, permitiendo una evaluación de la BLDF en función de las longitudes de onda de excitación y emisión1.

La medida de la BLDF fue tomada en las geometrías resultantes de la combinación de las siguientes direcciones de irradiación (subíndice “i”) y detección (subíndice “d”): ángulo polar: θi = 0º, 8º, 15º, 30º, 45º, 60º; θd = 0º - 80º (en pasos de 5º); ángulo azimutal: φi = 0º; φd = 0º, 180º.

Al representar el espectro de excitación de fluorescencia para cada muestra en función de la dirección de observación, encontramos una simetría para la incidencia normal, que se va perdiendo a medida que aumentamos el ángulo de irradiación. Además, este espectro decae con el ángulo de observación y con pendientes más pronunciadas para los ángulos de irradiación más altos. La Fig. 1. representa este espectro para la muestra USFS-200-020 (Azul/Blanco). La goniofluorescencia no presentó diferencias significativas entre las cinco muestras, lo que sugiere que es independiente del color.

Fig. 1. Dependencia del espectro de excitación con el ángulo de irradiación y detección.

Agradecimientos: A la comunidad de Madrid por la financiación del proyecto SINFOTON-CM: S2013/MIT-2790, así como al proyecto EMRP IND52 xD-Reflect, financiado por los países participantes de EURAMET y la Unión Europea.

Referencias: [1] Bernad, B., Ferrero, A., Pons, A., Hernanz, M. L., Campos, J., “Upgrade of goniospectrophtometer GEFE for near-field scattering and fluorescence radiance measurements”, Proc. SPIE 9398, Measuring, Modeling, and Reproducing Material Appearance 2015, 93980E (2015); doi:10.1117/12.2077084.

32 Ver póster

VER TODOS LOS PÓSTERES

Institución organizadora

Grupo de Displays y Aplicaciones Fotónicas (GDAF)

Universidad Carlos III de Madrid c/o Dra. Carmen Vázquez García

Avda. de la Universidad, 30

E-28911, Leganés, Madrid (España)

Phone: +34 91 624 9191

E-mail: cvazquez@ing.uc3m.es

El consorcio de SINFOTÓN-CM está formado por grupos de investigación de la Universidad Carlos III de Madrid, Universidad Politécnica de Madrid, Universidad de Alcalá de Henares, Universidad Rey Juan Carlos, Consejo Superior de Investigaciones Científicas y tres laboratorios de la Red de Laboratorios de la Comunidad de Madrid. Para más información visite http://www.sinfoton-cm.es/