Search

This work presents the application of an experimental nematic liquid crystal (LC) mixture (1929) in a large aperture lens. The LC material is composed of terphenyl and biphenyl derivatives compounds with an isothiocyanate terminal group and fluorinated lateral substituents. The substitution with a strongly polar isothiocyanate group and an aromatic rigid core provides $$\pi$$ π -electron coupling, providing high birefringence ($$\Delta n = 0.3375$$ Δ n = 0.3375 at 636 nm and 23 °C) and low viscosity ($$\eta$$ η = 17.03 mPa s). In addition, it also shows high values of birefringence at near infrared (0.318 at 1550 nm). The synthesis process is simple when comparing materials with high melting temperatures. The excellent properties of this LC mixture are demonstrated in a large aperture LC-tunable lens based on a transmission electrode structure. Thanks to the particular characteristics of this mixture, the optical power is high. The high birefringence makes this LC of specific interest for lenses and optical phase modulators and devices, both in the visible and infrared regions.

Quasi-dark resonances exhibiting antiferromagnetic order are theoretically investigated in a near-infrared metasurface composed of square slotted rings etched in a thin silicon layer on glass substrate. Access to the quasi-dark mode is achieved by reducing the symmetry of the metasurface according to the findings of a detailed group theory analysis. A thorough finite-element study reveals the key optical properties of the antiferromagnetic order quasi-dark mode, namely resonant wavelengths, quality factors, angular dispersion, and its robustness against optical extinction losses. It is demonstrated that the thickness of the silicon metasurface can adjust the asymmetry degree of the resonant Fano lineshape without affecting substantially its quality factor. Furthermore, tuning of the resonant wavelength can be achieved without significant modification of the Fano lineshape by controlling the angle of incidence of the impinging planewave. Overall, the work presents an all-dielectric, near-infrared metasurface for the excitation of sharp resonances with antiferromagnetic order, which can find use in emerging applications based on this particular configuration of artificial optical magnetism and/or strong field confinement and light-matter interaction. This work was supported by the CNR-FAPESP biennial (2022–2023) bilateral project StReAM “Strongly Resonant All-dielectric Metasurfaces based on quasi-dark and toroidal modes”. V.D. and H.E.H.F. thank the Brazilian Agency National Council of Technological and Scientifc Development (CNPq) for the fnancial support. H.E.H.F. was also funded by the São Paulo State Science Foundation (FAPESP), under the Project No 2015/24517-8, and by the Coordination for the Improvement of Higher Education Personal (CAPES)-PRINT/Institutional Internationalization Program, under Process No 88887.574915/2020-00. J.F.A. received funding from Ministerio de Ciencia, Innovación y Universidades of Spain under Juan de la Cierva-Incorporación grant and he also acknowledges the support of the projects PID2019-107270RB-C21 and PID2019-109072RB-C31 funded by MCIN/AEI/10.13039/501100011033 and FEDER “A way to make Europe”, PDC2021-121172-C21 funded by MCIN/AEI/10.13039/501100011033 and the European Union “Next generation EU”/PTR, and project S2018/ NMT-4326 funded by the Comunidad de Madrid and FEDER Program.

[Poster of]: 16th Topical Meeting on the Optics of Liquid Crystals. Sopot, 13th-18th of September, 2015, Poland. Nematic liquid crystal (LC) based beam steering have been reported for wide applications. However, for conventional nematic LC beam steering the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. The aim of this work has been focused on designing and theoretically analyzing a novel beam steering based on polymer stabilized blue phase liquid crystal (PSBPLC). This special mesophase of the chiral doped nematic LC has several advantageous characteristics. For example, a microsecond response time (approximately ten times faster than NLC) due to the double-twist cylinder diameter and short coherence length. A simulation program estimates the electrical field inside the structure solving the Gauss' law by FEM. An isotropic initial state is considered. The induced birefringence, and the ordinary and extraordinary refractive indices, are calculated in each mesh point. Orientation of the electrical field vector determines the optical axis orientation. The induced optical anisotropy of the PS-BPLC is considered. With this information and adopting the extended Jones matrix, the related electro-optical properties are estimated. Authors acknowledge funding support from the Spanish Ministerio de Economía y Competitividad (grants nº TEC2013-47342-C2-2-R and nº TEC2013-50138-EXP) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. No publicado

[Poster presented at]: XXII Conference on Liquid Crystals: Chemistry, Physics and Applications (CLC’2018), 17-21 September, 2018, Jastrzębia Góra, Poland. The THz range has gained great attention in recentyears. Due to the long wavelength of THz rays,conventional scaling of LC devices from the visible tothe THz range results in thicker devices with theunderlying disadvantages. A further option to overcomethese drawbacks is to use metamaterials.In this study, an active fishnet metamaterial based onhigh birefringence liquid crystal materials, is proposedand theoretically analyzed. Low absorption and lowrefractive index substrates (HDPE) coated with thicklayers of ITO (acting as a reflective layer at THz) areused. Apart from providing the electromagneticresonances that lead to negative refractive index, theITO layers also serve as the electrodes for theapplication of the control voltage. The latter allows forthe tuning of the metamaterial key parameters, suchas transmittance and effective permittivity orpermeability. This work was supported by the Research and Development Program through the Comunidad de Madrid (SINFOTON S2013/MIT-2790), the funding from Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) for the Project TEC2016-77242-C3-1-R AEI/FEDER,UE. Finally, N. Bennis, thank the Polish Ministry of Science and Higher Education (Statutory Activity PBS-654 of Military University of Technology). No publicado

[Proceeding of]: META'16: The 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics: July 25-28, 2016, Málaga, Spain. In this work, we propose and design a dielectric metasurface based on Silicon (Si)subwavelength pillars. A previous study of the directional conditions of the scattering is carried out inorder to obtain the optimum sizes. The metasurface can operate as a band-stop filter to realize blocking back THz waves in the designed band range, while transparent transmission over the rest of the range. This work has been supported by Ministerio de Economía y Competitividad of Spain (grant no. TEC2013-50138-EXP & TEC2013-47342-C2-2-R) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. Publicado

[Proceeding of]: META'16: The 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics: July 25-28, 2016, Málaga, Spain. In this paper, we demonstrate that for silicon nanopillars an optimum aspect ratio can be found, at which the overlapped electric and magnetic dipole resonances provide an optimized minimum forward scattering. This optimum shape depends on the aspect ratio, wavelength and refractive index of the surrounding medium. We work in the frame of numerical simulations based on Maxwell equations solved by finite element method. These results are promising for design and create novel flat optical devices. This work has been supported by Ministerio de Economía y Competitividad of Spain (grant no. TEC2013-50138-EXP & TEC2013-47342-C2-2-R) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. Publicado

[Proceeding of]: META'16: The 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics: July 25-28, 2016, Málaga, Spain. In this work we analyze the sensitivity of the directional scattering conditions in semiconductor nanodisks with the polarization of the incident light. The possibility to reach or not this directional scattering as a function of the polarization of the incident beam could be very interesting for the design of new all-optical devices for optical communications and computing. This work has been supported by Ministerio de Economía y Competitividad of Spain (grant no. TEC2013-50138-EXP) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. Publicado

Mención Internacional en el título de doctor, This thesis began with the project “Advanced Devices of Liquid Crystal and Electroluminescent Organic Diodes. Hybrid Applications for 3D Vision” funded by the Spanish government. The goal of this project was the development of optical devices to achieve 3D vision in portable devices without glasses or external elements. In order to achieve the goals of this project, solutions based on liquid crystal are considered. Specifically, adaptive micro-optical phase modulators based on liquid crystal technology are researched in depth. The gradient of the refractive index varies spatially the phase delay experienced by an impinging wavefront of a light beam. By using this effect, any refractive optical element may be reproduced with the proper voltage gradient applied to the sample. This is the main operating principle of the micro-optical phase modulators proposed in this thesis. As original contribution of this thesis, a novel algorithm to solve the position of a nematic liquid crystal molecular director is proposed. Once the liquid crystal is completely characterized, the developing of a specific model to know the electro-optic response of the micro-optical phase modulators is also relevant. Another original contribution is a novel equivalent electric circuit for modeling liquid crystal microlenses. An interesting feature of the model is that it provides an analytical solution for microlenses with modal and hole-patterned electrode schemes, by using a simple software tool. The required driving scheme (modal or hole-patterned) can be predicted. These theories have been validated by experimental results. For more complex devices, the equations are solved by Finite Element Method. A new manufacturing protocol is proposed to make the first set of modal microlens arrays. As a first step simple devices (monopixel cells) are fabricated in order to do a complete study of the liquid crystal electro-optical behavior. The characterization of the liquid crystal electro-optical parameters is determinant in order to design more complex devices. Refractive index and permittivity are the most important features considered. These parameters have been characterized to validate the proposed theoretical modelling of the liquid crystal molecular position. These devices have required special fabrication processes as well as a special characterization set-up especially in terms of size resolution or arrangement complexity. A custom micropositioner is developed and control software is programmed in relation to these tasks. The software automates the characterization process giving directly measured results of: phase modulation, focal distance, thickness or aberrations. These results have made it possible to validate experimentally the proposed electrical modeling for micro-optical devices. Demonstration of the viability of the liquid crystal lenticular technology has been carried out for an autostereoscopic application. This scheme provides the observer with the option of changing between horizontal and vertical views through his portable autostereoscopic display. Finally, last research contributions of this work of thesis have taken advantage of the deep knowledge of the electro-optical properties of lenticular devices for autostereoscopic applications, to guide the design of refined micro-optical phase modulators. Adaptive axicons and optical vortices are specially emphasized because their relevance from both, the scientific and technological point of view., Esta tesis se inició con el proyecto de investigación “Dispositivos avanzados de cristal líquido y diodos orgánicos electroluminiscentes. Aplicaciones híbridas para visión 3D”, financiado por el gobierno español. El objetivo de este proyecto consistía en el desarrollo de dispositivos ópticos para lograr visión 3D en dispositivos portátiles sin necesidad de gafas o elementos externos. Con el fin de alcanzar los objetivos de este proyecto, se consideran soluciones basadas en cristal líquido. En concreto, moduladores adaptativos de fase micro-ópticos basados en tecnología de cristal líquido. El gradiente del índice de refracción varía espacialmente el retardo de fase experimentado por un frente de onda incidente. Mediante el uso de este efecto, cualquier elemento óptico refractivo puede ser reproducido mediante un gradiente de tensión adecuado aplicado a la muestra. Este es el principio de funcionamiento de los moduladores de fase micro-ópticos propuestos en esta tesis. Como aportación original de esta tesis, se propone un nuevo algoritmo para resolver el director molecular de un cristal líquido nemático. Una vez que el cristal líquido está completamente caracterizado, es necesario el desarrollo de un modelo específico para saber la respuesta electro-óptica de los moduladores de fase micro-ópticos. Otra contribución original, consiste en un circuito eléctrico equivalente para el modelado de microlentes de cristal líquido. Una característica interesante del modelo es que proporciona una solución analítica para microlentes con esquemas de electrodos modales y “hole patterned”. Se puede predecir la topología necesaria en función de los parámetros de construcción. Estas teorías han sido validadas por resultados experimentales. Para los dispositivos más complejos, las ecuaciones se resuelven por el método de elementos finitos. Se propone un nuevo protocolo de fabricación para hacer microlentes modales. Como primer paso se fabrican dispositivos sencillos (células monopixel) con el fin de hacer un estudio completo del comportamiento electro-óptico del cristal líquido. La caracterización de los parámetros electro-ópticos de cristal líquido es determinante para diseñar dispositivos más complejos. El índice de refracción y la permitividad son las características más importantes. Estos parámetros se han caracterizado para validar el modelo teórico de la posición molecular de cristal líquido. Estos dispositivos han requerido procesos de fabricación complejos, así como montajes de caracterización determinados. Se ha desarrollado un microposicionador y un software de control. El software automatiza el proceso de caracterización dando resultados de: modulación de fase, distancia focal, grosor o aberraciones. Estos resultados han permitido validar experimentalmente el modelado eléctrico propuesto para dispositivos micro-ópticos. La demostración de la viabilidad de la tecnología propuesta se ha llevado a cabo mediante un dispositivo autoestereoscópico. Este dispositivo ofrece al observador la opción de cambiar entre vistas horizontal y vertical a través de su pantalla autoestereoscópica portátil. Finalmente, los últimos aportes de investigación de este trabajo de tesis se han aprovechado del profundo conocimiento de las propiedades electro-ópticas de los dispositivos lenticulares para aplicaciones autoestereoscópicas. Se pueden destacar los axicones adaptativos y vórtices ópticos por su relevancia tanto desde el punto de vista científico como tecnológico., Este trabajo ha sido desarrollado en el marco de los proyectos TEC2009-13991-C02-01 financiado por el Ministerio de Ciencia e Innovación y FACTOTEM2 S2009/ESP-1781 financiado por la Comunidad de Madrid., Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y Automática, Presidente: Ignacio Raúl Matías Maestro.- Secretario: Antonia Isabel Pérez Garcilópez.- Vocal: Dimitrios C. Zografopoulos

Reunión de Jóvenes Investigadores SINFOTON: 2ª Feria de Otoño 2016 In this work we analyze the sensitivity of the directional scattering conditions in semiconductor nanodisks with the polarizationof the incident light. The possibility to reach or not this directional scattering as a function of the polarization of the incidentbeam could be very interesting for the design of new all-optical devices for optical communications and circuitry. This work has been supported by Ministerio de Economía, Industria y Competitividad of Spain through projects TEC2013-47342-C2-2-R, TEC2012-38901-C02-01 and TEC2013-50138-EXP and the Comunidad de Madrid under program SINFOTON-CM (S2013/MIT-2790). B. García-Cámara, J.F. Algorri, J.M. Sánchez-Pena and R. Vergaz also acknowledge support from European Commision through EU Cost Action IC1208. Publicado

[Poster of]: Reunión de Jóvenes Investigadores SINFOTON: 2ª Feria de Otoño 2016. Three-diqensional vision has acquired great importance in audiovisual industry in the past ten years. Despite this, the first generation of autostereoscopic displays failed to generate enough consumer excictement. Sime reasons are few 3D content and performance issues... This work was supported by the Research and Development Programa through the Comunidad de Madrid (SINFOTON S2013/MIT 2790), the Ministerio de Economía y Competitividad of Spain (TEC2013-47342-C2-2-R). Publicado

[Poster of]: ¿SINFOTONes en el Año de la Luz?: Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015, 23 de Octubre. 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 [3] and tunable optical vortices [5]. TEC2013-47342-C2-2-R and SINFOTON S2013/MIT-2790 Publicado

[Proceeding of]: META'15: The 6th International Conference on Metamaterials, Photonic Crystals and Plasmonics: August 4-7, 2015, New York, USA Magneto-dielectric response of semiconductor nanoparticles has been recently shown asa useful phenomenon for several applications, e.g. sensors. The enhancement and spectral tuning ofthis behavior is a keynote aspect for some of these approaches. In this work, we show that the Mieresonances of nanoparticles composed of AlxGa1-xAs can be enhanced and tuning in a fine way bycontrolling the relation between the particle size and the concentration of Al atoms (x). This work has been supported by Ministerio de Economía y Competitividad of Spain under project TEC2013-50138-EXP. Publicado

Los nanotubos de carbono (NTC) y sus propiedades anisótropas presentan un gran interés en la investigación científica actual. Asociados a cristales líquidos (CLs), poseen propiedades eléctricas y electroópticas de gran interés. Mediante la aplicación de un campo eléctrico, las moléculas que forman los CLs se reorientan debido a su anisotropía dieléctrica, lo cual conlleva cambios en la permitividad dieléctrica y en el índice de refracción en la dirección del campo eléctrico. Debido a esta propiedad, los CLs pueden usarse en la elaboración de multitud de dispositivos electroópticos, tanto displays como dispositivos fotónicos capaces de manipular haces luminosos. El dopado del CL con NTC altera las propiedades dieléctricas de los CLs dependiendo de la orientación de estas nanopartículas. La capacidad de controlar la orientación de los NTC cuando están inmersos en estos materiales, abriría la posibilidad a variar las propiedades de los CL a voluntad y con ello desarrollar nuevos avances en los dispositivos fotónicos de CL. Teniendo en cuenta que los NTC presentan propiedades eléctricas anisótropas, se ha estudiado su reorientación dentro del medio CL empleando espectroscopía de impedancia. Los resultados muestran una clara dependencia de la posición de los NTC en el medio con el campo eléctrico, llegando incluso a cambiar el comportamiento eléctrico equivalente del dispositivo de capacitivo (célula de cristal líquido sin dopar) a uno resistivo (célula dopada con NTCs).

[Poster of]: 16th Topical Meeting on the Optics of Liquid Crystals. Sopot, 13th-18th of September, 2015, Poland. An ideal spiral phase plate based on liquid crystal and high resistivity layers is proposed and theoretically analyzed. The proposed structures generates a spiral-like voltage with simple voltage control... Authors acknowledge funding support from the Spanish Ministerio de Economía y Competitividad (grants nº TEC2013-47342-C2-2-R and nº TEC2013-50138-EXP) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. No publicado

[Poster of]: ¿SINFOTONes en el Año de la Luz?: Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015, 23 de Octubre. 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. 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. Publicado

[Proceeding of]: META'15: The 6th International Conference on Metamaterials, Photonic Crystals and Plasmonics: August 4-7, 2015, New York, USA The thermo-optical response of polydimethylsiloxane (PDMS) doped with metallic nanoparticles is theoretically studied. The temperature dependence of the effective refractive index of the mixture has been analyzed through the spectral evolution of the output power ratio of a beam crossing a sample. Both the nanoparticle size and the concentration effects have been analyzed to design a potential temperature sensor. Authors acknowledge funding support from the Spanish Ministerio de Economía y Competitividad (grants no. TEC2013-47342-C2-2-R and no. TEC2013-50138-EXP) and the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid. Publicado

El presente proyecto consiste en caracterizar un conmutador basado en fibra óptica de plástico y cristal líquido a través de la caracterización individual de sus componentes (cristales líquidos, polarizadores, PBS, etc.) para distintas longitudes de onda. Para poder desarrollar satisfactoriamente este proyecto se plantean una serie de objetivos. Los objetivos planteados en este trabajo son: Determinar el tipo de montaje necesario para caracterizar los diferentes elementos ópticos. Realización del montaje necesario para caracterizar polarizadores, PBS y cristales líquidos. Estudiar la respuesta de estos elementos para distintas longitudes de onda: rojo, verde e infrarrojo. Establecer que elementos son más adecuados para unas longitudes de onda concretas, las potencias alcanzables, las pérdidas de inserción y el crosstalk para cada uno de ellos. Usando los datos anteriores, se pretende diseñar un conmutador óptico multifunción basado en cristal líquido, capaz de trabajar en un amplio rango de longitudes de onda y adecuado tanto para redes POF como GI-POF. Ingeniería Técnica en Sistemas de Telecomunicación