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.

Thanks to its compatibility with the current CMOS technology and its potential of seamless integration with electronics, silicon photonics has been attracting an ever-increasing interest in recent years from both the academia and industry. By applying silicon photonic technology in microwave photonics, on-chip integration of microwave photonic systems could be implemented with improved performance including a much smaller size, better stability and lower power consumption. This thesis focuses on developing silicon-based photonic integrated circuits for microwave photonic applications. Two types of silicon-based on-chip devices, waveguide Bragg gratings and optical micro-cavity resonators, are designed, developed, and characterized, and the use of the developed devices in microwave photonic applications is studied. After an introduction to silicon photonics and microwave photonics in Chapter 1 and an overview of microwave photonic signal generation and processing in Chpater2, in Chapter 3 a silicon-based on-chip phase-shifted waveguide Bragg grating (PS-WBG) is designed, fabricated and characterized, and its use for the implementation of a photonic temporal differentiator is experimentally demonstrated. To have a waveguide grating that is wavelength tunable, in Chapter 4 a tunable waveguide grating is proposed by incorporating a PN junction across the waveguide grating, to use the free-carrier plasma dispersion effect in silicon to achieve wavelength tuning. The use of a pair of wavelength-tunable waveguide gratings to form a wavelength-tunable Fabry-Perot resonator for microwave photonic signal processing is studied. Thanks to its electrical tunability, a high-speed electro-optic modulator, a tunable fractional-order photonic temporal differentiator and a tunable optical delay line are experimentally demonstrated. To increase the bandwidth of a waveguide grating, in Chapter 5 a linearly chirped waveguide Bragg grating (LC-WBG) is designed, fabricated and evaluated. By incorporating two LC-WBGs in two arms of a Mach-Zehnder interferometer (MZI) structure, an on-chip optical spectral shaper is produced, which is used in a photonic microwave waveform generation system based on spectral-shaping and wavelength-to-time (SS-WTT) mapping for linearly chirped microwave waveform (LCMW) generation. To enable the LC-WBG to be electrically tuned, in Chapter 6 a lateral PN junction is introduced in the grating and thus an electrically tunable LC-WBG is realized. By incorporating two tunable LC-WBGs in a Michelson interferometer structure, an electrically tunable optical spectral shaper is made. By applying the fabricated spectral shaper in an SS-WTT mapping system, a continuously tunable LCMW is experimentally generated. Compared with a waveguide Bragg grating device, an on-chip optical micro-cavity resonator usually has a much smaller dimension, which is of help to increase the integration density and reduce the power consumption. Different on-chip optical micro-cavity resonators are studied in this thesis. In Chapter 7, an on-chip symmetric MZI incorporating multiple cascaded microring resonators is proposed. By controlling the radii of the rings, the MZI could be designed to have a spectral response with a linearly-varying free spectral range (FSR), which could be used in photonic generation of an LCMW, and to have a multi-channel spectral response with identical channel spacing, which could be used in the implementation of an independently tunable multi-channel fractional-order temporal differentiator. To further reduce the footprint of an optical micro-cavity resonator, in Chapter 8 an ultra-compact microdisk resonator (MDR) with a single-mode operation and an ultra-high Q-factor is proposed, fabricated and evaluated, and its use for the implementation of a microwave photonic filter and an optical delay line is experimentally demonstrated. To enable the MDR to be electrically tunable, in Chapter 9 an electrically tunable MDR is realized by incorporating a lateral PN junction in the disk. The use of the fabricated MDR in microwave photonic applications such as a high-speed electro-optic modulator, a tunable photonic temporal differentiator and a tunable optical delay line is experimentally demonstrated.

This thesis presents the synthesis methods and the characterizations of magnetic Fe3O4 nanoparticles, silica spheres with Fe3O4 nanoparticles embedded, and three dimensional magnetic photonic crystals (MPCs) prepared from the spheres. The structure, material composition, magnetic and optical properties, photonic band gaps (PBGs), as well as how these properties depend on the concentration of the magnetic nanoparticles, are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), superconducting quantum interference device (SQUID), Faraday rotation (FR) and optical spectrophotometers. Well-organized, face center cubic (fcc)-structured, super-paramagnetic 3D MPCs have been obtained and their PBGs are investigated through optical spectra. Fe3O4 nanoparticles are synthesized by standard co-precipitation method and a rapid mixing co-precipitation method with particle size varied from 6.6 nm to 15.0 nm at different synthesis temperature (0°C ~ 100°C). The obtained Fe3O4 nanoparticles, which show crystalline structure with superparamagnetic property, are embedded into silica spheres prepared at room temperature through a sol-gel method using the hydrolysis of tetraethyl orthosilicate (TEOS) in a base solution with different concentrations. By controlling the synthesis conditions (e.g., chemicals, the ratio of chemicals and stirring time), different size of MPC spheres in range of 75 nm to 680 nm has been obtained in a narrow distribution. The sphere suspensions in ethanol are dropped on glass substrate in the permanent magnetic field to achieve well organized 3D MPCs with (111) triangular close packed crystal plane of fcc structure parallel to the surface of substrate. From the transmission & forward scattering spectra (TF), five PBGs have been distinguished for these MPCs and they are defined as 1st, 2nd, 3rd, 4th and 5th PBGs according to the order of peaks that appear in mathematic fitting analysis. The positions (peak wavelengths) of PBGs show sphere size dependence: with the increase of the sphere size, they increase linearly. Comparing with pure SiO2 PCs at certain sphere size, the positions of PBGs for MPCs containing moderate Fe3O4 conc. (4.3 wt. %) are at longer wavelengths. On increasing the Fe3O4 conc., however, the PBGs shift back to shorter wavelength. The PBGs shift to longer or shorter wavelength is due to the combined effect of refractive index n increasing, as well as the increase of refractive index difference Δn, which are caused by the embedded Fe3O4 nanoparticles. The transmission spectra (T) with varied incidence angle of p- and s- polarized light are studied, obtaining angular dependent and polarization sensitive PBGs. It is found that with the increase of the incidence angle, the 1st PBGs shift to shorter wavelength while the 3rd ones shift to longer wavelength. High Fe3O4 conc. MPCs (6.4 wt. %) show enhancement of this angular dependence. It is also found that the PBGs show dependence on the polarize direction of incident light. Normally, at a certain incidence angle the PBGs sift more for p- polarized incident light than for s-polarized light with respect to normal incidence. This polarized dependence can also be enhanced for high Fe3O4 conc. MPCs. With a high concentration of Fe3O4 nanoparticles, the polarization sensitivity of p- and s- increased. These PBG properties indicate applications of 3D MPCs as functional optical materials, coatings, wavelength and polarization fibers for fiber optical communications devices and dielectric sensors of magnetic field, etc.. / QC 20110224

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Cette thèse apporte une contribution théorique et expérimentale à l'exploration des propriétés de dispersion et de polarisation de structures à cristaux photoniques à gradient (GPhCs). Nous explorons pour commencer la relation qui existe entre les déformations des surfaces équi-fréquences (EFS) de différents cristaux photoniques et les paramètres de maille des configurations envisagées. Compte tenu de la complexité des structures possibles obtenues à partir d'un chirp spatial bidimensionnel d'au moins un paramètre de maille, nous avons limité notre étude à un type particulier de structure basé sur un réseau carré de silicium sur isolant (SOI) planaire constitué de trous d'air de facteur de remplissage variable. Une expression analytique des EFS connexes en fonction du rayon des motifs a d’abord été extraite, et une structure GPhC de "référence" a ensuite été proposé pour l'exploration des propriétés de dispersion et de polarisation des GPhCs utilisant à la fois une approche consistant à propager un ou plusieurs rayons optiques dont les trajectoires sont données par les équations de l’optique Hamiltonienne et une approche tout numérique basée sur des simulations FDTD. Nous décrivons ensuite les processus de fabrication de salle blanche des structures à cristaux photoniques graduels, obtenues à partir de substrats semiconducteurs par lithographie par faisceau d'électrons et gravure ionique réactive. Les échantillons fabriqués sont étudiés expérimentalement par des techniques de mesure en champ lointain et en champ proche (SNOM) en s'appuyant sur une collaboration avec un autre groupe du CNRS. Les résultats expérimentaux montrent une relation dispersive quasi-linéaire de 0.25μm/nm dans la gamme de longueur d’onde allant de 1470nm à 1600nm. Les premiers dispositifs fabriqués présentent aussi la possibilité de séparer des couples de deux longueurs d'onde (démultiplexage) avec des pertes d'insertion faibles (inférieures à 2 dB) et un niveau de diaphonie faible (de l'ordre de -20 dB). Ils présentent également un effet très net de séparation des polarisations de la lumière avec une diaphonie inter-polarisations TE/TM de -27dB dans une bande spectrale de l’ordre de 70 nm. Au-delà de ces mesures optiques obtenus dans une configuration particulière de cristal photonique graduel, les travaux présentés dans cette thèse ont permis l'observation directe de la transition entre les régimes d’homogénéisation et de diffraction de propagation de la lumière dans un matériau optique artificiel tout diélectrique. Globalement, la méthodologie présentée et adoptée pour l'étude de la propagation de la lumière dans les structures étudiées a ouvert des perspectives pour la réalisation de fonctions optiques plus complexes. / This PhD thesis brings a theoretical and experimental contribution to the exploration of dispersive and polarization properties of graded photonic crystal (GPhC) structures. We first present a quantitative relationship between the deformations of the equi-frequency surfaces (EFSs) of different photonic crystals and the lattice parameters of the considered configurations. Considering the complexity of the possible GPhC structures made of a two-dimensional spatial chirp of at least one lattice parameter, we limit in this thesis our study to one particular type of GPhC structure based on a square lattice silicon on insulator (SOI) planar photonic crystal with a variable air hole filling factor profile. An analytical expression of the related EFSs as a function of the varied lattice parameter is extracted, and a GPhC “reference” structure is then proposed for the exploration of the dispersive and polarization properties of GPhCs using both Hamiltonian optic-assisted ray tracing as well as FDTD simulations. The clean room fabrication process of this GPhC structure family, which is based on electron beam lithography and reactive ion etching technologies, is reported. Fabricated samples are experimentally studied by far-field and near-field (SNOM) measurement techniques relying on a collaboration with a CNRS group of the Bourgogne university. Experimental results show an almost linear dispersive relationship of 0.25µm/nm in the 1470nm-1600nm spectral range. The fabricated samples also present the possibility for two-wavelength demultiplexing with low insertion loss (below 2dB) and low crosstalk level (around -20dB), and a polarization beam splitting effect with a crosstalk of -27dB in a 70nm bandwidth. Beyond these optical metrics obtained in one particular GPhC configuration, the works presented in this thesis have allowed the direct observation of the transition between the homogeneous and diffraction regimes of light propagation in an artificial optical all-dielectric material, and the presented and adopted methodology for the study of light propagation in GPhC structures has raised open perspectives for the realization of more complex optical functions in forthcoming works using low loss and flexible metamaterial-like photonic crystals.

Photonic crystals (PhCs) are structures periodic in thedielectric constant. They exhibit a photonic bandgap, i.e., arange of wavelengths for which light propagation is forbidden.Engineering of defects in the PhC lattice offers new ways toconfine and guide light. PhCs have been manufactured usingsemiconductors and other material technologies. This thesisfocuses on two-dimensional PhCs etched in InP-based materials.Only recently, such structures were identified as promisingcandidates for the realization of novel and advanced functionsfor optical communication applications. The primary focus was on fabrication and characterization ofPhC structures in the InP/GaInAsP/InP material system. Thedemands on fabrication are very high: holes as small as100-300nm in diameter have to be etched at least as deep as 2µm. Thus, different etch processes had to be explored andspecifically developed for InP. We have implemented an etchingprocess based on Ar/Cl2chemically assisted ion beam etching (CAIBE), thatrepresents the state of the art PhC etching in InP. Different building blocks were manufactured using thisprocess. A transmission loss of 10dB/mm for a PhC waveguide, areflection of 96.5% for a 4-row mirror and a record qualityfactor of 310 for a 1D cavity were achieved for this materialsystem. With an etch depth of 4.5 µm, optical loss wasfound to be close to the intrinsic limit. PhC-based opticalfilters were demonstrated using (a) a Fabry-Pérot cavityinserted in a PhC waveguide and (b) a contra-directionalcoupler. Lag effect in CAIBE was utilized positively to realizehigh quality PhC taper sections. Using a PhC taper, a couplingefficiency of 70% was demonstrated from a standard ridgewaveguide to a single line defect PhC waveguide. During the course of this work, InP membrane technology wasdeveloped and a Fabry-Pérot cavity with a quality factorof 3200 was demonstrated. Keywords:photonic crystals, photonic bandgap materials,indium phosphide, dry etching, chemically assisted ion beametching, reactive ion etching, electron beam lithography,photonic integrated circuits, optical waveguides, resonantcavities, optical filtering, finite difference time domain,plane wave expansion.

Photonic crystals (PhCs) are periodic dielectric structures that exhibit a photonic bandgap, i.e., a range of wavelength for which light propagation is forbidden. The special band structure related dispersion properties offer a realm of novel functionalities and interesting physical phenomena. PhCs have been manufactured using semiconductors and other material technologies. However, InP-based materials are the main choice for active devices at optical communication wavelengths. This thesis focuses on two-dimensional PhCs in the InP/GaInAsP/InP material system and addresses their fabrication technology and their physical properties covering both material issues and light propagation aspects. Ar/Cl2 chemically assisted ion beam etching was used to etch the photonic crystals. The etching characteristics including feature size dependent etching phenomena were experimentally determined and the underlying etching mechanisms are explained. For the etched PhC holes, aspect ratios around 20 were achieved, with a maximum etch depth of 5 microns for a hole diameter of 300 nm. Optical losses in photonic crystal devices were addressed both in terms of vertical confinement and hole shape and depth. The work also demonstrated that dry etching has a major impact on the properties of the photonic crystal material. The surface Fermi level at the etched hole sidewalls was found to be pinned at 0.12 eV below the conduction band minimum. This is shown to have important consequences on carrier transport. It is also found that, for an InGaAsP quantum well, the surface recombination velocity increases (non-linearly) by more than one order of magnitude as the etch duration is increased, providing evidence for accumulation of sidewall damage. A model based on sputtering theory is developed to qualitatively explain the development of damage. The physics of dispersive phenomena in PhC structures is investigated experimentally and theoretically. Negative refraction was experimentally demonstrated at optical wavelengths, and applied for light focusing. Fourier optics was used to experimentally explore the issue of coupling to Bloch modes inside the PhC slab and to experimentally determine the curvature of the band structure. Finally, dispersive phenomena were used in coupled-cavity waveguides to achieve a slow light regime with a group index of more than 180 and a group velocity dispersion up to 10^7 times that of a conventional fiber. / QC 20100712

<p>Photonic crystals (PhCs) are structures periodic in thedielectric constant. They exhibit a photonic bandgap, i.e., arange of wavelengths for which light propagation is forbidden.Engineering of defects in the PhC lattice offers new ways toconfine and guide light. PhCs have been manufactured usingsemiconductors and other material technologies. This thesisfocuses on two-dimensional PhCs etched in InP-based materials.Only recently, such structures were identified as promisingcandidates for the realization of novel and advanced functionsfor optical communication applications.</p><p>The primary focus was on fabrication and characterization ofPhC structures in the InP/GaInAsP/InP material system. Thedemands on fabrication are very high: holes as small as100-300nm in diameter have to be etched at least as deep as 2µm. Thus, different etch processes had to be explored andspecifically developed for InP. We have implemented an etchingprocess based on Ar/Cl₂chemically assisted ion beam etching (CAIBE), thatrepresents the state of the art PhC etching in InP.</p><p>Different building blocks were manufactured using thisprocess. A transmission loss of 10dB/mm for a PhC waveguide, areflection of 96.5% for a 4-row mirror and a record qualityfactor of 310 for a 1D cavity were achieved for this materialsystem. With an etch depth of 4.5 µm, optical loss wasfound to be close to the intrinsic limit. PhC-based opticalfilters were demonstrated using (a) a Fabry-Pérot cavityinserted in a PhC waveguide and (b) a contra-directionalcoupler. Lag effect in CAIBE was utilized positively to realizehigh quality PhC taper sections. Using a PhC taper, a couplingefficiency of 70% was demonstrated from a standard ridgewaveguide to a single line defect PhC waveguide.</p><p>During the course of this work, InP membrane technology wasdeveloped and a Fabry-Pérot cavity with a quality factorof 3200 was demonstrated.</p><p><b>Keywords:</b>photonic crystals, photonic bandgap materials,indium phosphide, dry etching, chemically assisted ion beametching, reactive ion etching, electron beam lithography,photonic integrated circuits, optical waveguides, resonantcavities, optical filtering, finite difference time domain,plane wave expansion.</p>

Optical properties of nanoscopic materials have been intensively pursued over last couple of decades due to their tunable optical properties. Recent interests in this field have been mainly focused on the preparation of ordered arrays of nano materials and study of their optical properties. These interests have been motivated by the applications of such systems for nano photonic devices. Theoretical predictions from such systems reveal complex absorption and emission properties, different from individual ones mainly because of energy transfer between them. These properties can be controlled further by preparing hybrid arrays of nanostructures, including nano crystals of different types. Hybrid arrays with semiconductor quantum dots and metallic nanoparticles are an example of such system. Optical properties of such a system can be tuned by controlling the interaction between excitons and plasmons. This thesis presents the experimental studies on optical properties of polymer capped nanoparticles, quantum dot arrays and hybrid arrays with semi conducting quantum dot and metal nanoparticles. A brief summary of the experimental methods and results have been highlighted below. In this thesis, we study the controlling decay dynamics of CdSe quantum dots by 2D photonic-plasmonic and metamaterial templates. In Chapter 1 we provide a detailed background on the theoretical methods of Light-Matter interaction at nano scale. We also have given the detailed information on both weak and strong coupling region in the light-matter interaction. This chapter includes the discussion controlling light-matter interaction with both photonic crystals and plasmonic materials with some appropriate examples from the literature. In this chapter we have also explained the relevance of our work in this area and organization of the chapters and there importance has given. In chapter 2 we provide details about various experimental methods used in this thesis. A brief introduction is given on the materials used, their synthesis and the preparation of different type of self assembled plasmonic-photonic templates. This chapter starts with an explanation of the materials used along with the justification; moves on to the preparation of different 2D wire metamaterial. The characterization techniques for these different types of templates like spectroscopic ellipsometer, atomic force spectroscopy, scanning electron microscopy and transmission electron microscopy are discussed. We also discussed optical spectroscopic techniques like confocal optical microscopy and near field optical microscopy techniques. The first two chapters form the basis of all the experiments discussed in the forth coming chapters. In chapter 3 Finite difference time domain (FDTD) simulations were performed on two different plasmonic sub wavelength photonic templates embedded with CdSe quantum dots. Tunable loading of these templates with plasmonic nano antenna allowed control of the emission from the embedded quantum dots. We discuss how large loading of nano antenna can effectively control the optical density of states for the quantum dots leading to enhancement of their radiative decay rates as observed in experiments. On the other hand, at low level of loading, while FDTD fails to capture the observed enhancement of decay rates in experiment, an alternative mechanism is suggested to exist in such cases. Thus, subtle interplay of multiple mechanisms engineered by appropriate placement and loading of plasmonic nano antenna in such templates is demonstrated as an effective method to control optical density of states and hence spontaneous emission of embedded quantum dots. In Chapter 4 we report results of controlled tuning of the local density of states (LDOS) in versatile, flexible and hierarchical self assembled plasmonic templates. Using 5 nm diameter gold (Au) spherical nano antenna within a polymer template randomly dispersed with quantum dots, we show how the photo-luminescence intensity and lifetime anisotropy of these dots can be significantly enhanced through LDOS tuning. Finite difference time domain simulations corroborate the experimental observations and extend the regime of enhancement to a wider range of geometric and spectral parameters bringing out the versatility of these functional plasmonic templates. It is also demonstrated how the templates act as plasmonic resonators for effectively engineer giant enhancement of the scattering efficiency of these nano antenna embedded in the templates. Our work provides an alternative method to achieve spontaneous emission intensity and anisotropy enhancement with true nanoscale plasmon resonators. In chapter 5 we reported enhancement optical properties of quantum dot monolayers on top of the functional, flexible and hierarchical self-assembled plasmonic template using extremely small gold (Au) nanoparticles of diameter 5 nm. We reported how the LODS changes with different polarizations for CdSe quantum dot present on top of the template. We observed the enhanced radiative LDOS from the nano antenna filled pores indicating plasmonic enhanced emission from these templates. The difference in spectral and spatial profile of LDOS and Pur-cells with polarization of quantum dot emission results in the anisotropic emission in these templates. In chapter 6 we reported the emergence of strong coupling between quantum emitters and 2D hyperbolic metamaterials (HMM). We studied both spectral dependence and effect of filling fraction of the HMM on strong interaction. We also show the controlling of the transition from weak coupling region to strong coupling region by changing the distance between QD monolayer and HMM. By using FDTD simulation we are able to calculate both spectral function S(!) and coupling efficiency. In chapter 7 as a conclusion we concluded the work done in this thesis. We also indicated the future directions in this field and possible application.

Nano-emitters are the new generation of laser devices. A photonic-crystal cavity, which highly confines light in small volumes, in combination with quantum-dots can enhance the efficiency and lower the threshold of this device. The practical realisation of a reliable, electrically pumped photonic-crystal laser at room-temperature is, however, challenging. In this project, a design for such a laser was established. Its properties are split up into electrical, optical and thermal tasks that are individually investigated via various device simulations. The resulting device performance showed that with our design the quantum-dots can be pumped in order to provide gain and to overcome the loss of the system. Threshold currents can be as low as 10’s of μA and Q-factors in the range of 1000’s. Gallium arsenide wafers were grown according to our specifications and their diode behaviour confirmed. Photonic-crystal cavities were fabricated through a newly developed process based on a TiOₓ hard-mask. Beside membraned cavities, also cavities on oxidised AlGaAs were fabricated with help to a unique hard-mask removal method. The cavities were measured with a self-made micro-photoluminescence setup with the highest Q-factor of 4000 for the membrane cavity and a remarkable 2200 for the oxide cavity. The fabrication steps, regarding the electrically pumped photonic-crystal laser, were developed and it was shown that this device can be fabricated. During this project, a novel type of gentle confinement cavity was developed, based on the adaption of the dispersion curve (DA cavity) of a photonic-crystal waveguide. Q-factors of as high as 600.000 were measured for these cavities made in Silicon.