The concept of photonic crystals was born in the late 1980's when two important letters were published that showed the possibility to control light propagation by a periodic structure. A photonic crystals consists of two or more materials with different dielectric functions periodically arranged on the length scale of light. If the conditions are favorable, a gap will open in the dispersion relation, often called photonic band structure, and electromagnetic waves with frequency in the gap range cannot propagate through the photonic crystal. In this thesis, mainly two types of structures and their properties have been numerically investigated: two-dimensional structures that are either square or triangular. In the calculations, both dielectric and polaritonic materials have been used. Polaritonic materials have an interval of high reflectance in the IR range, due to strong lattice resonances. Within such an interval, the real part of the dielectric function is negative, which causes a metal-like behavior. A polaritonic material, BeO has been introduced in photonic crystals to study the coexistence of structure and polaritonic gaps. Band structures and for some cases transmission spectra have been calculated to study the existence of complete gaps, i.e. energy intervals in which an incoming electromagnetic wave is totally reflected regardless of polarization and angle of incidence. A brief discussion on signature management and thermal emission, and calculations for low-emittance coatings is included. It is shown that a 50-60µm layer of a 3D photonic crystal can be sufficient to achieve a thermal emittance of 20%.

This dissertation describes a theoretical and experimental study on coherent thermal emission from thin-film multilayer structures. A novel multilayer structure consisting of a one-dimensional photonic crystal and a polar material (or a metal) is proposed as a coherent thermal-emission source. Surface electromagnetic waves can be excited at the edge of photonic crystal, enabling coherent emission characteristics (i.e., spectral- and directional-selectivity in the emissivity). A near-infrared coherent emission source is designed and fabricated using vacuum deposition and chemical vapor deposition techniques. Measurements were performed using a Fourier-transform infrared spectrometer and a laser scatterometer. The agreement between the resonance conditions obtained from experiments and the calculated dispersion relation confirms that surface waves at the photonic crystal-metal interface can be utilized to build coherent thermal-emission sources. The second part of this dissertation focuses on the energy propagation direction in near-field thermal radiation. The energy streamline method based on the Poynting vector is applied to near-field thermal radiation by incorporating the fluctuational electrodynamics, in which thermal emission is viewed as originated from random motion of electric dipoles at temperatures above absolute zero. It is shown that the Poynting vector is decoupled for each parallel wavevector component due to the randomness of thermal emission. The spectral radiative energy travels in infinite directions along curved lines; this is a fundamental characteristic of near-field thermal radiation. The findings in this dissertation are important for the design of near-field optical sensors and energy conversion devices.

Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research. / text

Observing and controlling solid state quantum systems is an area of intense research in quantum science today. Such systems offer the natural advantage of being bound into a solid device, eliminating the need for laser cooling and trapping of atoms in free space. These solid state "atoms" can interface directly with photonic channels designed to efficiently couple into larger networks of interacting quantum systems. With all of the tools of semiconductor fabrication technology available, the idea of scalable, chip-based quantum networks is a tantalizing prospect. / Physics

This thesis establishes methods to locally and effciently detect the fluorescence from photonic crystals (PCs) in dependence on wavelength and direction. These are applied to three dimensional (3D) PCs grown by vertical deposition of polystyrene beads. The experiments allow conclusions about the local 3D structure of a sample, about defects in its volume and about spatial structural variations. They thus provide more information than typical spectroscopy measurements that average over large areas and methods that only image the surface structure like scanning electron microscopy. A focused laser is used to excite emitters in the sample only locally. The fluorescence is then collected by a microscope objective. Every point in this objective’s back focal plane (BFP) corresponds to a certain direction. This property is utilized in two ways. When observing a small spectral range of the emission in the BFP, stop bands appear as intensity minima since they hinder the emission into the corresponding directions. Thus, back focal plane imaging (BFPI) allows to visualize stop bands of many directions at the same time. The detected patterns permit to find the in-plane and out-of-plane orientation of the PC lattice and to conclude on the presence of stacking faults. Spatial variations of the structure are observed on a length scale of a few micrometers. The depth of the stop band is reduced at sample positions, where structural changes occur. In back focal plane spectroscopy (BFPS), a slit selects light from certain points in the BFP, which is spectrally dispersed subsequently. This allows to record spectra from many directions simultaneously. From them, a lattice compression along the sample normal of about 4% is found. Small deformations are also observed for other directions. Scattering at defects redistributes the emission. This increases the detected intensity compared to homogeneous media at some stop band edges in a broad spectral range for samples thicker than the scattering mean free path. Thinner samples show a narrow enhancement due to an increase in the fractional density of optical states and thus in emission. BFPI and BFPS are also used to observe the growth of PCs from drying droplets. The experiments show that the beads initially form a non-close packed lattice. This causes stress as the lattice constant decreases, which is released by cracking of the PCs.

An efficient simulation technique for calculating the current distribution in a Vertical Cavity Surface Emitting Laser (VCSEL) is proposed and implemented. The technique consists of a hybrid 1D/3D approach to the problem. The 3D aspect of simulation is essential for devices like a photonic crystal VCSEL where the existing 2D simulation techniques are inadequate. The modular approach of the technique is advantageous, as it provides exibility in dealing with device simulations of varying complexity. It also provides a relatively short simulation time, beneficial for exploring a large design parameter space. The box integration technique is used for discretizing the equations and sparse matrix methods are used in solving the matrices. Simulation results and comparisons are provided for various aspects and modules of the simulator. The results for a few sample simulations indicate that the analysis has reasonable agreement with experimental results. The simulation error can be reduced using more accurate models for the active region of the laser.

In recent years, Silicon Photonics has emerged as a promising technology for cost-effective fabrication of photonic components and integrated circuits, the application of which is recently expanding in technological fields beyond tele- and data-communications, such as sensing and biophotonics. Compact, energy-efficient laser sources with precise wavelength control are crucial for the aforementioned applications. However, practical, efficient, electrically-pumped lasers on Silicon or other group IV elements are still absent, owing to the indirect bandgap of those materials. Consequently, the integration of III-V compounds on Silicon currently appears to be the most viable route to the realization of such lasers. In this thesis, I present and explore the potential of an External Cavity (EC) hybrid III-V/Silicon laser design, comprising a III-V-based Reflective Semiconductor Optical Amplifier (RSOA) and a Silicon reflector chip, based on a two-dimensional Photonic Crystal (PhC) cavity vertically coupled to a low-refractive-index dielectric waveguide. The vertically coupled system functions as a wavelength-selective reflector, determining the lasing wavelength. Based on this architecture mW-level continuous-wave (CW) lasing at room temperature was shown both in a fiber-based long cavity scheme and die-based short cavity scheme, with SMSR of > 25 dB and > 40 dB, respectively. Furthermore, by electrically modulating the refractive index of the PhC cavity in the reflector chip, tuning of the emitted wavelength was achieved in the die-based short cavity EC laser configuration. In this way, I demonstrated the suitability of the examined EC configuration for direct frequency modulation. The proposed scheme eliminates the need for wavelength matching between the laser source and a resonant modulator, and reveals the potential of employing low-power-consumption resonant modulation in practical Silicon Photonics applications.

O objetivo do presente trabalho foi o estudo e análise da resposta óptica de dispositivos de cristal fotônico uni-dimensional (1D) fabricados através do uso da tecnologia de silício poroso. Os resultados obtidos neste trabalho apresentam contribuições significativas no desenvolvimento de uma tecnologia para a fabricação de dispositivos ópticos em silício. As principais contribuições deste trabalho estão direcionadas ao aprimoramento dos processos de fabricação de cristais fotônicos 1D e processos de tratamento térmico. Os resultados da análise estrutural através de microscopia óptica de varredura (MEV) e da resposta óptica (refletância ou absorbância) mostraram que dispositivos de cristal fotônico fabricados em soluções altamente diluídas de HF apresentam melhor desempenho, tendo sido otimizado o processo de fabricação utilizando-se uma célula de duplo compartimento (célula dupla). A otimização da resposta óptica dos dispositivos foi atribuída ao efeito de minimização das rugosidades de interface e minimização de efeitos de anisotropia na taxa de corrosão durante o processo de anodização eletroquímica. O processo eletroquímico utilizado para a fabricação de cristais fotônicos 1D apresentou limitação quanto ao número máximo de camadas, sendo observado que dispositivos com número de camadas acima de 60 apresentavam degradação das suas camadas superficiais, comprometendo a resposta óptica do dispositivo. Este resultado foi atribuído a efeitos de diluição química das camadas expostas à solução por longos períodos de processo. Os dispositivos fotônicos 1D mostraram-se sensíveis a processos de recozimento térmico, deslocando suas bandas fotônicas proibidas para regiões de menor comprimento de onda devido à mudança do índice de refração das camadas e aos efeitos de expansão e compressão das camadas constitutivas do dispositivo. Os dispositivos de micocavidade Fabry-Perot mostraram-se mais sensíveis aos processos de recozimento térmico. Os resultados obtidos no presente trabalho vislumbram grandes possibilidades de aplicação dos cristais fotônicos de PS na fabricação de dispositivos ópticos na tecnologia de silício como filtros, lentes, cavidades ressonantes, guias de ondas, grades de difração e dispositivos sensores. / The aim of the present work was to study and analyze the optical response of one- dimensional (1D) photonic crystal devices obtained by using the porous silicon technology. The experimental results obtained from this work showed the significant contribution to the development of a technological process for optical device fabrication in the silicon substrate. The most important contributions of the work are pointed out to improve the electrochemical process for device fabrication and thermal annealing process in order to improve the optical response of the devices. The results obtained from Scanning electronic microscopy (SEM) and from the optical response of the devices, showed that devices fabricated in the double cell and diluted HF solution improved their optical response due to minimization of the anisotropy of corrosion rate and decreasing of the surface roughness between layers. The electrochemical process used for device fabrication showed the existence of limitation on the numbers of layers because of the existence of chemical dissolution effect that became important for long time process. The 1D photonic crystal devices in PS technology showed high sensibility to thermal annealing process, due to the refraction index change after thermal annealing the photonic band gap position shift down to low wavelength region. The Fabry-Perot devices showed higher sensibility to thermal annealing process improving their optical response after annealing process. The results obtained from the present work showed that the PS 1D photonic device could be applied to optical devices fabrication in silicon technology such as optical filters, lenses, resonant cavities, wave-guide devices, diffraction grade and optical sensor device.

Ce travail porte sur l’étude des mécanismes de conversion de fréquences dans les cristaux photoniques non linéaires bidimensionnels. En particulier, nous avons étudié la génération paramétrique optique (GPO) dans les cristaux de LiTaO3 (PPLT- 2D) à réseau carré. Nous nous sommes d’abord intéressés à l’étude théorique et numérique de structures PPLT- 2D. Une étude numérique, nous a permis de comprendre la contribution des vecteurs de réseau réciproque (kmn) pour différents types de réseaux, en particulier les réseaux carrés et rectangulaires. Par simulations numériques, nous avons également étudié l’influence de l’angle incidence du faisceau de pompe sur l’efficacité de conversion paramétrique dans ses structures. Les mesures expérimentales nous ont permis de mettre en évidence, pour la première fois, l’existence de plusieurs singularités où le signal est partagé pour générer deux idlers et vice versa. En effet, en analysant les propriétés spectrales et angulaires des faisceaux à la sortie du cristal, nous avons, expérimentalement et numériquement, identifié les contributions impliquées dans ces processus communs de GPO. De plus, nous avons étudié le management du gain paramétrique optique dans un réseau carré de PPLT-2D. Les résultats montrent que l’exploitation de la direction non colinéaire permet d’augmenter le gain suivant deux angles d’incidences de la pompe : 0.8° et 1.6°. Cela implique, une meilleure efficacité de conversion en minimisant le walk-off entre la pompe et l’idler. Dans ces conditions, le gain pourrait être proche de celui de la direction colinéaire. Un bon accord a été constaté entre les résultats expérimentaux et ceux de la simulation. / This work deals with the study of the mechanisms of frequency conversion in two-dimensional nonlinear photonic crystals. In particular, we have studied optical parametric (OPG) generation in square-lattice LiTaO3 crystals (PPLT-2D). We first focused on the theoretical and numerical study of PPLT-2D structures. A numerical study allowed us to understand the contribution of the reciprocal lattice vectors (kmn) for different types of gratting, in particular square and rectangular lattices. By numerical simulations, we also studied the influence of the incidence angle of the pump beam on the efficiency of the parametric conversion in these structures. Experimental measurements have allowed us to demonstrate, for the first time, the existence of several singularities where the signal is shared to generate two idlers and vice versa. Indeed, by analyzing the spectral and angular properties of the beams at the output of the crystal, we have experimentally and numerically identified the contributions involved in these common OPG processes. In addition, we studied the management of the optical parametric gain in a square lattice of PPLT-2D. The results show that the use of the non-collinear direction makes it possible to increase the gain according to two angles of incidence of the pump: 0.8 ° and 1.6 °. This implies, better conversion efficiency by minimizing the walk-off between the pump and the idler. Under these conditions, the gain could be close to that of the collinear direction. A good agreement was found between the experimental results and those of the simulation.

Pesquisas de desenvolvimento na área de fotônica impressa vão desde sistemas óticos de reflexão e espalhamento de luz, até moduladores e dispositivos fotônicos na escala nanométrica. Para isso, os dispositivos fabricados utilizam das propriedades de estruturas capazes de controlar a emissão e propagação luminosa a níveis elevados de confinamento e guiamento. Estas estruturas são conhecidas como cristais fotônicos. No entanto, os cristais fotônicos encontram dificuldades de aplicação, pois são produzidos por métodos intermitentes e em pequena escala. Neste sentido, este estudo contribuiu para o desenvolvimento de um método de fabricação de cristais coloidais em larga escala. O processo consistiu em depositar nanoesferas de sílica com diferentes diâmetros e em diferentes substratos através da ferramenta wire-bar via processamento Roll-to-Roll. Para o desenvolvimento do trabalho as nanoesferas de sílica foram sintetizadas seguindo o método Stöber e caracterizadas quanto a distribuição dos diâmetros. As imagens das nanoesferas obtidas por Microscopia Eletrônica de Varredura (MEV) foram analisadas pelo software ImageJ®, constatando-se a monodispersividade das esferas. Posteriormente, para a deposição das partículas sobre os substratos, os parâmetros de deposição foram ajustados a fim de produzir um filme monocamada de cristais coloidais em um arranjo hexagonal compacto. Desenvolvemos também uma equação que prediz a concentração ótima das suspensões coloidais, em função dos parâmetros de processamento e o ordenamento de rede, para produzir o filme monocamada. Assim, foram alcançadas estruturas organizadas que exibiram o efeito iridescente mediante a variação do ângulo da luz incidente. Diante das propriedades óticas e periodicidade da rede dos cristais coloidais, propusemos aplicações como adesivos reflexivos, camada anti-reflexo para células solares e superfícies melhoradas para amplificação do sinal SERS. As estruturas utilizadas em SERS apresentaram limite de detecção para a molécula de Rodamina 123 da ordem de 10-6 M. De maneira geral, este trabalho contribuiu para o desenvolvimento de um método de deposição de cristais coloidais em larga escala através do processamento Roll-to-Roll, que se mostrou bastante versátil, uma vez que permite a aplicação das estruturas fabricadas em diferentes áreas tecnológicas e fácil controle dos parâmetros de processamento. / Development research in printed photonics goes from optical systems of reflection and scattering of light, to modulators and photonic devices at the nanometer scale. For this, the devices manufactured use the properties of structures capable of controlling the emission and light propagation at high levels of confinement and guidance. These structures are known as photonic crystals. However, the photonic crystals find application difficulties because they are produced by intermittent and small scale methods. In this sense, this study contributed to the development of a large-scale method of manufacturing colloidal crystals. The process consisted in depositing silica nanospheres with different diameters and in different substrates through the wire-bar tool in Roll-to-Roll processing. For the development of this work the silica nanospheres were synthesized following the Stöber method and characterized by distribution of diameters. The images of nanospheres obtained by Scanning Electron Microscopy (SEM) were analyzed by ImageJ® software, confirming the monodispersivity of the spheres. Subsequently, for the deposition of the particles on the substrates, the deposition parameters were adjusted to produce a monolayer film of colloidal crystals in a compact hexagonal arrangement. We have also developed an equation that predicts the optimal concentration of the colloidal suspensions, as a function of the processing parameters and the network ordering, to produce the monolayer film. Thus, organized structures were achieved which exhibited the iridescent effect by varying the angle of incident light. Considering the optical properties and periodicity of the colloidal crystals arrangement, we have proposed applications such as reflective adhesives, anti-reflective layer for solar cells and improved surfaces for amplification of SERS signal. The structures used in SERS showed limit of detection for Rhodamine 123 molecule in the order of 10-6 M. In general, this work contributed to the development of a large-scale method of deposition of colloidal crystals through Roll-to-Roll processing, which proved quite versatile, since it allows the application of of fabricated structures in different technological áreas and easy control of processing parametres. In general, the Roll-to-Roll method of colloidal crystals deposition proved to be quite versatile, since it allows the application of fabricated structures in different technological areas, easy control of processing parametres and large-scale production.