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Electrooptic materials, whose refractive index can be modified by external fields, can be employed to create tunable lenses with no movable parts, that result useful for many applications from spatial environment to mobile phone cameras and adaptive contact lenses. Liquid crystals are especially suitable for these applications since LC reorientation is relatively simple and low voltage driving signals are required. However, the design of tunable LC lenses is not simple. The main difficulty is to achieve optimized electrode profiles giving the right wavefront deformation to focus flat wavefronts into a single focal point without compromising the symmetry of the electrodes [1]. Regular lenses show very low power for any reasonable birefringence and cell thickness ?unless their size is reduced to microlenses; radial phase-wrapping devices like Fresnel diffractive lenses (FDL) are the best way to overcome this limitation. However, Fresnel lenses are made of a number of concentric electrodes, the larger the better, whose external electrical interconnection is extremely involved, requiring dozens of independent tracks that discontinue the circular electrodes and constrain the cell fill factor. In this work we have developed a device having independent azimuthal and radial phase-wrapping. This is a combination of a spiral phase plate and an FDL, giving a spiral diffractive lens. No internal connections are required; the fill factor is about 0.98. Divergent and convergent lenses (1? Ø, ±2.5 diopters) can be obtained from the same device (Fig. 1).

Photonic integrated circuits (PICs) have contributed to manipulation and routing of optical signals. PICs have been mainly based on silicon on insulator (SOI) technology, due to compatibility with conventional CMOS fabrication processes and also good performing in the near-infrared communication windows. Nevertheless, silicon is not convenient for other purposes that aim to exploit the visible spectrum.

When manufacturing a liquid crystal device of low or medium complexity (tens or hundreds of elements), the problem is often to find a way to address it electronically. In recent years, several families of microprocessors have appeared. These microprocessors are easily programmed at high level and can control electronic chips in a very simple way through I2C or SPI ports.

The interest in Photonic integrated circuits (PICs)is continuously increasing worldwide and nowadays it can not be dismissed that it willbecome one of the most revolutionary technologies of this century.During the last decades, integrated optics sector was mainly focused onsilicon on insulator (SOI)platform, due to compatibility with preceding CMOS industry. Nevertheless, other materials, such as silicon nitride, indium phosphide or polymers, have shown valuable features foremerging applications beyond communication.

Photonic Integrated Circuits (PICs) are the photonic equivalent to Electronic Integrated Circuits (EICs): integrated devices able to perform several optical or optoelectronic functions employing visible or near IR light rather than electrons to carry the signals.

Técnicas de fabricación en cámara limpia para la realización de guía ondas poliméricas 1-Introducci�ón Circuito fot�ónico integrado Cristal lí��quido 2-Circuitos fot�ónicos integrados Guía Ondas Dispositivos Fot�onicos 3- Diseño Simulación Integraci�on de LC en PICs 4- Fabricaci�ón 5- Logros Interruptor �óptico

Photonic integrated circuits (PICs) are devices that integrate multiple photonic functions. The visible light is guided between components by light waveguides of the same order as light wavelength, i.e. 1-5?m or even less [1]. Because of the size of connections, coupling light into PICs is a challenging task previous to characterizing them. The aim of our group is to turn a passive PIC into an active one by adding layers of electro-optics materials, either as a component within the light path, or deposited onto the waveguide affecting the evanescent field of the guided light. Testing the light behavior inside the PICs may be hampered by the arduous light coupling from external sources. This problem may be faced up from several points of view.

Microbial contamination of food, water and even air supply is a permanent threat against the health of humans and livestock. This threat is particularly serious in contexts such as hospitals (Legionella contamination of air-conditioning) and in extreme situations, such as those met in the third world and in natural crisis situations where water contamination is one of the most serious risks to human wellbeing.

The Polarization Maintaing Photonic Crystal Fiber PM-1550-01 has been employed to create intermodal interferometers by splicing short (cm) portions of PCF between two single mode fiber (SMF) pigtails and PANDA fibers. It has been shown that this setup generates a intermodal interferometer. The interferometers have been made tunable by the inclusion of liquid crystal inside the PCF portion.

A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions, being as such similar to electronic integrated circuits. The connections between components are made of light waveguides; these can be active themselves ?i.e., light paths can be externally controlled? by using electrooptic (EO) materials within or onto the light path. The likelihood of liquid crystals to become EO materials for active waveguides in PICs has been explored.

A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions, being as such similar to electronic integrated circuits. The connections between components are made of light waveguides; these can be active themselves -i.e., light paths can be externally controlled- by using electrooptic (EO) materials within or onto the light path. The likelihood of liquid crystals to become EO materials for active waveguides in PICs has been explored. A number of multimode interference coupler (MMI), Mach-Zehnder interferometers (MZI) and rings resonators (RRs) have been simulated, designed and manufactured [1]. PICs have been fabricated on silicon and glass. Waveguides have been arranged in the same wafer having widths 1.5-2 μm and lengths of active regions of 8-700 μm. In all cases, waveguides are made of SiO 2 (substrate) and SU8 (film), the cover being SiO 2 , so that an LC structure can be eventually adapted onto the waveguide set. Several LCs materials are being tested, with and without 3D-stabilization by a reactive mesogen. Reorientation of the LC mixture modifies the evanescent field of the guided light, effectively affecting the underneath light path. As a result, the MMI pattern, the MZI transfer function, and the RR resonant wavelength can be externally controlled.

Coupling light into a photonic integrated circuit (PIC) is usually the most challenging task to characterize these circuits. PIC connections between components are made of light waveguides whose section is often of the same order as light wavelength, i.e., 1-5 ?m or even less. Waveguides may become active by inserting additional layers of electrooptic materials [1], either as a component within the light path, or deposited onto the waveguide affecting the evanescent field of the guided light. Testing the light behavior inside the PIC and comparing the experimental results with those predicted in modeled circuits may be hampered by the tiny cross-section of the waveguides ?especially monomode guides? and the arduous light coupling from external sources.

An experimental results on birefringent photonic crystal fiber (PCF) selectively infiltrated with metallic nanoparticles (NPs) dispersed in polydimethylsiloxane (PDMS) are presented. In general, PCFs are structures consisting of periodic matrix of microholes surrounding core region, that can be either solid or hollow.

Liquid crystal devices are increasingly being used in non-display applications to manufacture small devices that can be driven by low voltage electronics. LCs are low cost, light weight and avoid using mechanical components. A wide number of interesting applications involve the use of LCs for phase modulation of light. This can be done with light propagating through the LC itself or rather with light propagating in a waveguide (WG) where sections of its cladding are filled with LC that interacts with the light?s evanescent field. Several device families based on this general outline are being tested in our group. The devices can be roughly classified into two categories. The first group consists of WGs having a width much larger than the light wavelength (Fig. 1), therefore behaving as 1D waveguides. In these structures, effective beam steering can be achieved using pixelated electrodes having specific shapes. Beam steering has been demonstrated in IR beams [1] using silicon substrates. In our laboratory, steering of visible light is tested employing, besides silicon substrates, ITO-coated glass substrates with a high-index guiding layer of SU-8.

This PhD work is focused on the development of polymer-based waveguides and devices and waveguides for integrated photonic circuits and sensing. The work covers all aspects of the device development starting with the initial device functionality concept followed by the simulation of the optical properties, then the lithographic design and the subsequent fabrication to the final device testing. Prior to the manufacture, the geometry and physical dimension of devices have been studied by simulating electromagnetic 2D modes as well as finite element methods for optical beam propagation. The devices have been designed using various CAD tools compatible with photomask manufacturing and CNC machining systems. The script generators are collected in an ad-hoc process design kit (PDK) for photonic chips. Existing manufacturing processes have been optimized and the technique of direct laser writing (DLW) has been improved. Devices have been manufactured not only by DLW, but also by conventional UV photolithography and e-beam lithography. Protocols for the depositing of controlled thin polymer layers by spinning have been established for various materials. Exposure dose tests have been performed reaching optimal dose for each material independently of lithography techniques employed. A photonic embedded device characterization setup for the visible light spectrum has been redesigned and optimized. The positioning accuracy of each part of the setup was greatly improved by adding motorized micrometric actuators. Liquid crystal (LC) as an active medium changing the optical properties of a waveguide and an integrated photonic device has been employed. A LC cell has been used as top cladding on a silicon nitride photonic chip. A Mach-Zehnder interferometer (MZI) was designed, in which one interferometric arm is exposed to the action of LC. By applying an electromagnetic field to the cell, LC molecules are reoriented, and hence the top cladding refractive index is modulated. It has been shown the variation of the MZI optical output intensity by applying an electric voltage to the LC cell. The entire production process flow has been validated by manufacturing a multimode interferometer (MMI) based on the polymers EpoCore and EpoClad. The device was fully designed, manufactured and characterized within this thesis. The chip layout was directly patterned into the polymer by e-beam lithography showing the adaptability of this material from UV- to electron-stimulated polymerization. Fabricated MMIs output power splitting ratio was characterized for an operating wavelength of 635 nm. Various device designs were manufactured and characterized to establish a PDK to be used to manufacture other MMIs on the same platform in the future. A very good correlation between the simulated and experimental measurements was revealed. This work aims to confirm polymer materials as a valid alternative to existing platforms for photonic integrated circuits (PICs) manufacture. Polymers are inexpensive compared with inorganic materials and the production process presented here can be potentially adapted to fast and cost-effective microfabrication methods, such as roll-to-roll or nanoimprint lithography. The compatibility of polymer-based integrated waveguides and devices with operation in the visible range and combination with flexible thin-film substrates, makes them a promising option to consider for the next PICs generation. Its impact will be superior in non-traditional fields, such as biosensing, in which inorganic materials have predominated so far and devices are designed to operate in the same wavelength bands historically used in telecommunications. Considering all of this, polymer PICs properties would be essential for Point-of-Care (PoC) applications and Lab-on-Chip development. RESUMEN Esta tesis doctoral se centra en el desarrollo de guías de onda y dispositivos para circuitos integrados fotónicos (PICs) basados en polímero. El trabajo engloba todos los aspectos del desarrollo de PICs, comenzando con el concepto inicial y la funcionalidad del dispositivo, seguido de la simulación de las propiedades ópticas y su diseño, su posterior fabricación y finalmente la validación. Antes de la fabricación, se ha estudiado la geometría y las dimensiones físicas de los dispositivos mediante la simulación de modos de propagación en 2D para guías de onda monomodo, y también mediante la simulación de elementos finitos de la propagación óptica en los dispositivos integrados. Los dispositivos han sido diseñados en varios lenguajes CAD tanto para la fabricación de máscaras de litografía, como para herramientas de mecanizado CNC. Los programas generadores de texto usados en los diseños se han recopilado en un kit de diseño de procesos (PDK) creado para chips fotónicos poliméricos. Se han optimizado los equipos de fabricación existentes y se ha mejorado la técnica de escritura láser directa (DLW). Los dispositivos se han fabricado utilizando DLW, y también fotolitografía ultravioleta y litografía por e-beam. Se han establecido protocolos para la creación de capas delgadas de polímero por el método de spin-coating en diversos materiales. Se han realizado pruebas para determinar la dosis óptima de exposición en cada técnica de litografía y para cada material estudiado. Se ha rediseñado y optimizado un montaje de caracterización de dispositivos fotónicos integrados para el espectro de luz visible. La precisión de posicionamiento del chip se mejoró notablemente mediante actuadores motorizados micrométricos. Se ha empleado el cristal líquido (LC) como medio activo que cambia las propiedades ópticas de la guía de onda y del dispositivo fotónico integrado. Para ello, se ha utilizado una célula de LC como capa superior en un chip fotónico de nitruro de silicio. El diseño del chip es un interferómetro de Mach-Zehnder (MZI), en el que la guía de onda de sensado está expuesta a la acción del LC. Se ha demostrado que la aplicación de un campo electromagnético a la celda de LC varía la intensidad de salida óptica del circuito fotónico. El proceso de producción en su totalidad ha sido finalmente validado mediante la fabricación de un dispositivo de interferencia multimodo (MMI), basado en los polímeros EpoCore y EpoClad. El dispositivo fue completamente diseñado, fabricado y caracterizado durante este proyecto. La fabricación se realizó mediante la técnica de litografía por e-beam que muestra la adaptabilidad de este material a la polimerización estimulada por electrones. La relación de potencia de salida óptica del MMI se caracterizó para una longitud de onda de 635 nm. Se fabricaron y caracterizaron varios diseños de MMIs para establecer un kit de diseño de procesos (PDK) que se utilizará para fabricar otros dispositivos integrados en la misma plataforma en el futuro. Se determinó que las medidas experimentales de la relación de potencias de salida óptica confirmaban los resultados de las simulaciones. Este trabajo pretende confirmar que los materiales poliméricos son una alternativa válida para la fabricación de circuitos integrados fotónicos (PICs). El método de producción mostrado puede fácilmente adaptarse para incluir métodos de fabricación más rápidos y rentables como el roll-to-roll y la nanoimpresión. Los dispositivos integrados hechos en polímero son compatibles con el funcionamiento en el espectro de luz visible y también con la integración en sustratos flexibles. Esto los convierte en una prometedora opción a considerar para la próxima generación de PICs. Su repercusión será mayor en campos no tradicionales, como los biosensores, en los que hasta ahora han predominado las plataformas basadas en materiales inorgánicos y los dispositivos son diseñados para operar en las bandas históricamente usadas en telecomunicaciones. De esta manera las propiedades de los PICs poliméricos serán esenciales para el desarrollo de aplicaciones de (PoC) o el Lab-on-Chip.

Las células de cristal líquido están normalmente formadas dos sustratos de cristal, recubiertos en su cara interna por electrodos de óxido de estaño e indio (ITO) u óxido de estaño fluorado (FTO). Sobre estos metales se deposita una capa de alineamiento, estando finalmente el cristal líquido contenido entre estos dos sustratos. Para el correcto funcionamiento de las células, es crítico verificar un correcto aislamiento entre electrodos antes de continuar con la fabricación. Para que, en caso de detectar errores, estos puedan ser corregidos durante la etapa inicial. Existen diferentes técnicas para la fabricación de estos electrodos siendo las más comunes la fotolitografía y la ablación láser. Una mala configuración de los parámetros de fabricación, como por ejemplo falta de potencia en el caso de la ablación laser, puede suponer que no se elimine correctamente el material obteniendo un aislamiento insuficiente entre electrodos. Para realizar estas comprobaciones es necesario medir la resistividad entre un gran número de electrodos. El objetivo de este proyecto es el desarrollo de un sistema automatizado capaz de medir la conductividad entre electrodos, permitiendo la detección de posibles errores de forma temprana. Con este fin, se ha realizado el diseño del circuito para la medición de la resistividad entre electrodos de una célula de cristal líquido. Posteriormente, se ha llevado a cabo un estudio sobre los componentes necesarios para implementar dicho circuito en una placa de circuito impreso (PCB). Finalmente, se ha diseñado la PCB mediante un programa de diseño electrónico, importando las huellas de los componentes necesarios y realizando el diseño de los esquemáticos. Por otro lado, se ha realizado la distribución de los componentes dentro de la placa y se ha llevado a cabo el enrutado. Con el fin de verificar el funcionamiento del circuito diseñado se ha realizado una prueba de concepto del mismo, detectando correctamente cortocircuitos y circuitos abiertos.

The last century was characterized by the extreme developing of the technology, being an essential part in our modern society. This evolution couldn’t be possible without the support of the electronics, resulting in the creation of the microelectronics. This field needs a high-resolution microscopy to verify the manufacturing processes. Advances in microscopy technology, resulted in, amongst many other inventions, the atomic force microscope (AFM). The atomic force microscope is a kind of scanning probe microscope. It is a high precision device capable of making topographies with nanometer resolution, by detecting the deflection caused by atomic interactions. This project aims at the developing of a low-cost AFM with a performance comparable to a commercial AFM, based in an optical pick-up unit (OPU) being the head of the microscope. This project covers the software and hardware design. The nano-positioners which drive the sample movement, are replaced with piezoelectric buzzers. In order to achieve that, a study of the implied electronics and the needed control is made. A 3D printed stage with nanometer resolution displacements is manufactured and the printed circuit boards (PCB’s) are mounted. After assembling it, their proper functioning is proved. The mechanical parts of the microscopes were made using a 3D printer. The OPU proved to be a suitable device for high precision measurements. The developed electronics control the AFM with nanometer resolution. The designed low-cost AFM has a performance close to a commercial one, although control software was not implemented.

In this project we aim at addressing the study of the full manufacturing process of a photonic integrated circuit, from the initial stage of components design to the tests required to ensure its proper functioning. Its most innovative aspect compared to the existing technology is that the wavelength used belongs to the visible light spectrum. Thus the dimensions of the waveguides have to be significantly reduced. For this reason, the analysis of new manufacturing protocols, using new materials and new techniques, is required. In addition, the current methods will be also modified in order to be optimized for our scenario. In a first step, design and simulation of the desired devices were conducted so that a set of different configurations can be approached. After that, the integration of the maximum number of these configurations was settled in a chromium mask design. This mask was then used in the photolithography process to harden SU-8 photoresist over a silicon substrate. Good fabrication results were obtained, being able to reach waveguides structures of 0.5 μm thick and 1.5 μm wide. The final chips were characterized in a dark room with two different laser input and proper light guidance was demonstrated as well as output switching.