Diminuer l'épaisseur de la couche d'absorbeur est une solution attractive pour produire des cellules photovoltaïques à coût réduit. Cela permet également de réduire la quantité de matériau actif utilisé ainsi que d'améliorer la collection du courant dans la cellule. Cette thèse s'est focalisée sur la conception de nanostructures pour exalter l'absorption de la lumière dans des couches de semiconducteur d'épaisseur réduite et ainsi proposer des cellules ultraminces efficaces.Dans un premier temps, nous avons proposé une approche originale pour piéger la lumière dans une cellule ultra-fine (≤ 100 nm) en silicium amorphe. Un réseau métallique est placé en face avant de la cellule déposée sur un miroir métallique afin d'obtenir une absorption multi-résonante large bande pour les deux polarisations de la lumière. Nous proposons aussi d'utiliser le réseau métallique comme une électrode transparente alternative afin de réduire les pertes optiques dans le contact avant de la cellule. Une analyse numérique approfondie des mécanismes résonants en jeu a été menée ainsi que la fabrication et la caractérisation optique de démonstrateurs.Dans un deuxième temps, nous avons appliqué ce concept de contact avant multi-résonant à des couches ultra-fines en arsenure de gallium (GaAs). Nous avons montré numériquement et expérimentalement le potentiel d'une nanogrille métallique bi-dimensionnelle pour le confinement efficace de la lumière dans 25 nm de GaAs.Enfin, nous avons étudié la possibilité de réduire l'épaisseur de cellules en silicium cristallin d'un facteur 10 à 100 par rapport à l'état de l'art. Nous avons développé un procédé pour transférer des couches de silicium cristallin de quelques microns d'épaisseur épitaxiées par PECVD sur un substrat hôte bas coût. Nous avons également travaillé à la structuration contrôlée de nanopyramides en vue d'un piégeage optique efficace dans ces couches minces. / Reducing the absorber thickness is an attractive solution to decrease the production cost of solar cells. Furthermore, it allows to reduce the amount of material needed and improve the current collection in the cell. This thesis has been focused on the design of nanostructures to enhance light absorption in very small semiconductor volumes in order to achieve efficient ultra-thin solar cells. First, we have proposed an original light-trapping concept for ultra-thin amorphous silicon (a-Si:H) solar cells. A one-dimensional metallic grating is patterned on the front surface of the cell deposited on a metallic mirror. Broadband multi-resonant absorption has been demonstrated for both light polarizations. The metallic grating is also used as an alternative transparent electrode in order to reduce optical losses in the front contact. A detailed analysis of the multi-resonant absorption mechanism has been carried out through numerical calculations. The fabrication and optical characterization of ultra-thin a-Si:H solar cells with metallic gratings have validated the multi-resonant approach.Second, we have proposed a design with a two-dimensional metallic grid as a resonant front contact for very thin (25 nm) gallium arsenide (GaAs) layers. We have shown through the design and fabrication of a proof-of-concept structure the potential of metallic nanogrids to confine efficiently light absorption with an ultra-thin GaAs layer.Finally, advanced light-trapping structures could also allow a thickness reduction of crystalline silicon wafers of a factor 20 to 100 with respect to state-of-the-art cells. We have developed a process to transfer micron-thick epitaxial crystalline silicon (c-Si) layers onto a low-cost host substrate. Inverted nanopyramids have also been fabricated in crystalline silicon in order to achieve a broadband anti-reflection effect. It opens promising perspectives towards the realization of double-sided nanopatterned ultra-thin c-Si cells.

Orientador: Newton Cesário Frateschi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-02T20:57:13Z (GMT). No. of bitstreams: 1 Souza_MarioCesarMendesMachadoDe_D.pdf: 15167961 bytes, checksum: b18ee3c5c89a54254813d054e000f1d7 (MD5) Previous issue date: 2017 / Resumo: Após duas décadas de progresso contínuo, a fotônica integrada apresenta-se como uma tecnologia indispensável, exibindo soluções para importantes demandas tecnológicas atuais como o tráfego e processamento de sinais ópticos ultra-rápidos. Ao mesmo tempo, ela permite avanços substanciais em áreas emergentes como o "laboratório-no-chip" (lab-on-a-chip). No entanto, enquanto funcionalidades básicas necessárias para a maioria das aplicações (fontes de luz, moduladores, filtros, linhas de atraso, detectores, etc.) já estão disponíveis em uma variedade de dispositivos e plataformas, alguns desafios ainda permanecem. Nos últimos quatro anos, estivemos interessados em identificar alguns desses desafios e fornecer abordagens interessantes para enfrentá-los. Esta tese, que engloba uma parcela importante dessas investigações, pode ser dividida em dois tópicos. No primeiro, apresentamos microresonadores acoplados como dispositivos que permitem um controle espectral flexível e reconfigurável. Explorando as características desses dispositivos, demonstramos novas funcionalidades como o controle reconfigurável do "splitting" entre ressonâncias, fornecemos novas ferramentas de modelagem como uma teoria de modos acoplados modificada e propomos um modulador que emprega anéis acoplados, capaz de superar a limitação entre eficiência de modulação e largura de banda enfrentada por moduladores baseados em um único anel. No segundo tópico apresentamos o desenvolvimento de um espectrômetro a transformada de Fourier integrado em um chip, utilizando fotônica de silício. Os desafios para obter esse dispositivo, como a não-idealidade inerente à plataforma de silício (dispersão e não-linearidade termo-ótica) são discutidos em detalhe, além da demonstração experimental que indica como tal dispositivo pode abrir caminho para espectrômetros portáteis robustos e econômicos / Abstract: After two decades of continuous progress, integrated photonics has proven its indisputable role as an enabling technology. It addresses important technological demands of our time such as ultrafast optical data transfer and processing while allowing substantial progress in emerging areas, including lab-on-a-chip. Although the basic functionalities required for most applications (light sources, modulators, filters, delay lines, detectors, etc.) are now available in a variety of designs and platforms, a few challenges remain and room for improvement can still be found. During the last four years, we have been interested in identifying some of these challenges and in providing interesting approaches to tackle a handful. This thesis, encompassing an important share of such investigations, can be divided into two topics. First, we present coupled microresonators as devices allowing for flexible and reconfigurable spectral control. Exploiting these devices, we demonstrate novel functionalities like the reconfigurable resonance-splitting control, we provide novel modeling tools such as a modified coupled mode theory, and we propose a coupled-ring modulator that overcomes the trade-off between modulation efficiency and bandwidth faced by single microrings modulators. The second topic addresses the realization of an on-chip Fourier transform spectrometer using silicon photonics. We discuss the challenges of realizing such device due to non-idealities inherent to the silicon platform (dispersion and thermo-optic non-linearity) and we provide an experimental demonstration indicating how this device can pave the way for robust and cost-effective portable spectrometers / Doutorado / Física / Doutor em Ciências / 156281/2013-9 / 2014/04748-2, 2015/20525-6 / CNPQ / FAPESP

表面等離子體激元和熒光分子之間的電磁相互作用已因廣泛應用於量子運算中的量子信息處理和分子生物技術的分子檢測而得到相當大的關注。雖然通過把熒光分子放置在電漿系統旁來改善熒光分子的發光度和方向性已被廣泛接受，但是了解表面等離子體激元和熒光材料之間的相互作用的物理亦是很重要的。 / 在這篇論文中，我們將研究在二維納米銀洞陣列上有機染料帶方向性的發光特性。通過量度在每個角度的反射和熒光發光光譜，我們可以繪製出二維納米銀洞陣列所產生的電磁共振模式的色散關係及熒光材料發光度與方向的關係。此外，在陣列上以不同方向行走的表面等離子體激元的衰變壽命亦被找出。我們亦將反射率和熒光發光光譜進行比較，從而發現熒光發光的加強跟表面等離子體激元的光譜位置、衰變後傳播的方向、它的衰變壽命和它的耦合效率有十分密切的關係。為了解背後的物理，我們建立了一個理論模型去區分能量從有機染料轉移到表面等離子體激元的過程與表面等離子體激元衰變過程對表面等離子體激元改變熒光材料發光度的影響。因此，我們可以對能量從有機染料轉移到表面等離子體激元的過程與方向的關係進行定量分析。最後，我們的研究結果與由有限差分時域模擬計算所得的結果吻合。結論得出在二維納米銀洞陣列上所實現的表面等離子體激元増加有機染料光提取效率與三維空間中方向的關係是源於電漿帶隙的產生所引致的態密度重整及分配。 / The electromagnetic interaction between surface plasmon polaritons (SPPs) and fluorescent molecules has been capturing considerable attention for a wide variety of applications ranging from quantum information processing in quantum computing to molecule detection in biotechnology. Although it is widely accepted that the light emission efficiency and directionality are improved by placing the fluorescent molecules in close proximity to a plasmonic system, the understanding of the physics on how SPPs interact with the fluorescent materials is of importance. / In this thesis, the directional emission properties of LDS organic dyes supported on two-dimensional Ag nanohole array is studied. Angle-resolved reflectivity and photoluminescence spectroscopy have been employed to map out the dispersion relations of electromagnetic resonance modes arising from the array and the dependence of plasmonic emission on emission angle. In addition, the decay lifetimes of SPP modes in different propagation directions in array have been determined. By comparing the reflectivity and photoluminescence mappings, we find that the emission enhancement is strongly correlated with the spectral and angular positions of SPP modes together with their lifetimes and coupling efficiencies. To understand the underlying physics, we have developed an analytical model to differentiate the surface plasmon mediated emission (SPME) into energy transfer from LDS to SPPs and the radiative decay of surface plasmons. As a result, the directional dependence of the energy transfer process can then be analyzed quantitatively. Finally, our results are compared with the finite-difference-time-domain simulations with good agreement. It is concluded that the directional dependence of the surface plasmon mediated emission is attributed to the redistribution of the density of states in the periodic nanohole array due to the opening of the plasmonic gaps. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chan, Kay Fung = 表面等離子體激元改變納米金屬洞陣列上發光材料的光提取效率 / 陳其鋒. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 115-123). / Abstracts also in Chinese. / Chan, Kay Fung = Biao mian deng li zi ti ji yuan gai bian na mi jin shu dong zhen lie shang fa guang cai liao de guang ti qu xiao lu / Chen Qifeng. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Surface plasmon polaritons (SPPs) and surface plasmon mediated emission (SPME) --- p.2 / Chapter 1.2 --- Directional surface plasmon mediated emission (SPME) on metallic nanohole array --- p.5 / Chapter 1.3 --- Our analytical model of surface plasmon mediated emission --- p.8 / Chapter 1.3.1 --- Formalism of rate equations --- p.8 / Chapter 1.3.2 --- Determination of the directional dependence of the coupling efficiency from decay rates of the SPP and the fluorescent material --- p.11 / Chapter 1.4 --- Organization of the thesis --- p.12 / Chapter Chapter 2 --- Theory of surface plasmon polaritons --- p.14 / Chapter 2.1 --- The Maxwell’s equations and the boundary conditions for electromagnetic waves --- p.14 / Chapter 2.2 --- Dielectric constant of metal --- p.18 / Chapter 2.3 --- Master equation for electromagnetic waves, the Bloch form of SPPs and the dispersion relation of SPPs at the interface between dielectric and metal --- p.19 / Chapter 2.4 --- Excitation of surface plasmon polaritons by grating coupling --- p.27 / Chapter 2.5 --- Decay of surface plasmon polaritons --- p.29 / Chapter 2.5.1 --- Non-radiative decay --- p.29 / Chapter 2.5.2 --- Radiative decay --- p.31 / Chapter Chapter 3 --- Experimentation and Simulation --- p.37 / Chapter 3.1 --- Sample preparation --- p.37 / Chapter 3.1.1 --- Interference lithography [2.2, 3.7, 3.8] --- p.37 / Chapter 3.1.2 --- E-beam evaporation --- p.39 / Chapter 3.1.3 --- Spin coating of florescence material --- p.40 / Chapter 3.2 --- Measurements --- p.41 / Chapter 3.2.1 --- Angle-resolved specular reflection measurement [3.10] --- p.42 / Chapter 3.2.2 --- Angle-resolved photoluminescence (PL) spectroscopy [3.11] --- p.43 / Chapter 3.2.3 --- K-space (Fourier space) imaging [3.12, 3.13, 3.14] --- p.44 / Chapter 3.3 --- FDTD --- p.46 / Chapter 3.3.1 --- Theory of FDTD --- p.46 / Chapter 3.3.2 --- Simulation of the reflectivity of plane wave --- p.52 / Chapter 3.3.3 --- Simulation of the field pattern with a dipole source --- p.55 / Chapter 3.3.3.1 --- Near-to-far field projection --- p.59 / Chapter 3.3.3.2 --- Near field pattern in k-space --- p.60 / Chapter Chapter 4 --- Analysis --- p.62 / Chapter 4.1 --- Angle-resolved reflectivity measurement --- p.62 / Chapter 4.1.1 --- SPP mode identification --- p.62 / Chapter 4.1.2 --- Wavelength dependence of uncoupled SPPs decay rates --- p.65 / Chapter 4.1.3 --- Directional dependence of uncoupled SPPs decay rates --- p.71 / Chapter 4.2 --- Angle-resolved PL spectroscopy --- p.79 / Chapter 4.2.1 --- Comparison with the angle-resolved reflectivity --- p.79 / Chapter 4.2.2 --- Differentiation of the resonance and off-resonance positions on the PL mapping --- p.81 / Chapter 4.3 --- K-space imaging --- p.83 / Chapter 4.3.1 --- Reflectivity and the comparison with the phase - matching equation --- p.83 / Chapter 4.3.2 --- k-space imaging of the PL emission --- p.85 / Chapter 4.4 --- Directional dependence of the emission factor --- p.86 / Chapter 4.5 --- Directional dependence of the coupling rate of the LDS emission to the SPP mode --- p.94 / Chapter 4.6 --- Near field in k-space from the FDTD method --- p.97 / Chapter Chapter 5 --- Conclusions --- p.113 / Bibliography --- p.115

Silicon photonics has emerged in recent years as one of the leading technologies poised to enable penetration of optical communications deeper and more intimately into computing systems than ever before. The integration potential of power efficient WDM links at the first level package or even deeper has been a strong driver for the rapid development this field has seen in recent years. The integration of photonic communication modules with very high bandwidth densities and virtually no bandwidth-distance limitations at the short reach regime of high performance computers and data centers has the potential to alleviate many of the bandwidth bottlenecks currently faced by board, rack, and facility levels. While networks on chip for chip multiprocessors (CMP) were initially deemed the target application of silicon photonic components, it has become evident in recent years that the initial lower hanging fruit is the CMP's I/O links to memory as well as other CMPs. The first chapter of the thesis provides more detailed motivation for the integration of silicon photonic modules into compute systems and surveys some of the recent developments in the field. The second chapter then proceeds to detail a technical case study of silicon photonic microring-based WDM links' scalability and power efficiency for these chip I/O applications which could be developed in the intermediate future. The analysis, initiated originally for a workshop on optical and electrical board and rack level interconnects, looks into a detailed model of the optical power budget for such a link capturing both single-channel aspects as well as WDM-operation-related considerations which are unique for a microring physical characteristics. The holistic analysis for the full link captures the wavelength-channel-spacing dependent characteristics, provides some methodologies for device design in the WDM-operation context, and provides performance predictions based on current best-of-class silicon photonic devices. The key results of the analysis are the determination of upper bounds on the aggregate achievable communication bandwidth per link, identifying design trade-offs for bandwidth versus power efficiency, and highlighting the need for continued technological improvements in both laser as well as photodetector technologies to allow acceptable power efficiency operation of such systems.The third chapter, while continuing on the theme silicon photonic high bandwidth density links, proceeds to detail the first experimental demonstration and characterization of an on-chip spatial division multiplexing (SDM) scheme based on microrings for the multiplexing and demultiplexing functionalities. In the context of more forward looking optical network-on-chip environments, SDM-enabled WDM photonic interconnects can potentially achieve superior bandwidth densities per waveguide compared to WDM-only photonic interconnects. The microring-based implementation allows dynamic tuning of the multiplexing and demultiplexing characteristic of the system which allows operation on WDM grid as well device tuning to combat intra-channel crosstalk. The characterization focuses on the first reported power penalty measurements for on-chip silicon photonic SDM link showing minimal penalties achievable with 3 spatial modes concurrently operating on a single waveguide with 10-Gb/s data carried by each mode. The chapter also details the first demonstration of WDM combined with SDM operation with six separate wavelength-and-spatial 10-Gb/s channels with error free operation and low power penalties. The fourth, fifth, and sixth chapters shift in topic from the application of silicon photonics to communication links to the evolving use of silicon waveguides for nonlinear all-optical processing. The unique tight mode confinement in sub-micron cross-sections combined with the high response of silicon have motivated the development of four-wave mixing (FWM)-based processing silicon devices. The key feature of the silicon platform for these nonlinear processing platforms is the ability to finely and uniformly control the dispersive properties of the optical structures in a way that enables completely offsetting the material dispersion and achieve dispersion profiles required for effective parametric interaction of waves in the optical structures. Chapter four primarily introduces and motivates nonlinear processing in communication applications and focuses on recent achievements in non-silicon and silicon FWM platforms. Chapter five describes some of the author's contributions on parametric processing of high speed data in silicon nonlinear devices, with first of a kind demonstrations of wavelength conversion of 160-Gb/s optically time division multiplexed (OTDM) data as well as the wavelength-multicasting of a 320-Gb/s OTDM stream. The chapter then details a methodical characterization and demonstration of several record wavelength conversion experiments of data in silicon with 40-Gb/s data wavelength-converted across more than 100 nm with only 1.4-dB of power penalties as well as the wavelength and format conversion of 10-Gb/s data across up to 168 nm with sensitivity gains stemming from the format conversion of about 2 dB and a residual conversion penalty of only 0.1 dB, achieved by implementing an improved experimental setup. Both experiments highlight the performance uniformity of the conversion process for a wide range of probe-idler detuning settings, showcasing the silicon platform's unique broadband phase matching properties. The sixth chapter presents a slight shift in motivation for parametric processing from traditional telecom-wavelength applications to functionalities developed targeting mid-IR operation. Parametric-processing in the silicon platform at long wavelengths holds large potential for performance improvements due to the elimination of two-photon absorption in silicon at long wavelengths as well as silicon's dispersion engineering capabilities which uniquely position the silicon platform for effective phase matching of significantly wavelength detuned waves. Four-wave mixing signal generation and reception at mid-IR wavelengths are attractive candidates for tunable flexible operation with modulation and detection speeds which are currently only available at telecom wavelengths. With this vision in mind, several contributions detailing extension of FWM functionalities in silicon to operate at wavelengths close to 2 μm with performance equivalent to much smaller detuning setting measurements. The contributions detail the experimental demonstration of the first silicon optical processing functionalities achieved at such long wavelengths including the wavelength conversion and unicast of 10-Gb/s signals with up to 700 nm of probe-idler detuning, the combined two-stage 10-Gb/s FWM-link in which both data generation and detection at 1900 nm is facilitated by parametric processing in silicon with only 2.1-dB overall penalty, the first ever 40-Gb/s receiver at 1900 nm based on a FWM stage for simultaneous temporal demultiplexing and wavelength conversion, and lastly, the demonstration of a 40-Gb/s FWM-link operation with only 3.6 dB of penalty. The chapter concludes with a short discussion on possible extensions to enable silicon parametric processing at even longer wavelengths targeting the mid-IR spectral transmission window of 3-5 μm.

Animals have evolved diverse strategies to control solar and thermal radiations so that they can better adapt to their natural habitats. Structured materials utilized by these animals to control electromagnetic waves often surpass analogous man-made optical materials in both sophistication and efficiency. Understanding the physical mechanism behind these structured materials of nature inspires one to create novel materials and technologies. Our optical and thermodynamic measurements of insects (Saharan silver ants and cocoons of the Madagascar comet moth) living in harsh thermal environments showed their unique ability to simultaneously enhance solar reflectivity and thermal emissivity, and to maintain a cool body temperature. Saharan silver ants, Cataglyphis bombycina, forage on the desert surface during the middle of the day. The ants’ conspicuous silvery glance is caused by a coating of hairs with unique triangular cross-sections. The hair coating enhances not only the reflectivity of the ant’s body surface in the visible and near-infrared range of the spectrum, where solar radiation culminates, but also the emissivity of the ant in the mid-infrared. The latter effect enables the animals to efficiently dissipate heat back to the surroundings via blackbody radiation under full daylight conditions. The fibers produced by the wild comet moth, Argema mittrei, are populated with a high density of air voids that have a random distribution in the fiber cross-section but are invariant along the fiber. These filamentary air voids strongly back-scatter light in the solar spectrum, which, in combination with the fibers’ intrinsic high emissivity in the mid-infrared, enables the cocoon to function as an efficient radiative-cooling device, preventing the pupa inside from overheating. The reduced dimensionality of the random voids leads to strong optical scattering in the transverse direction of the cocoon fibers. This enables tightly confined optical modes to propagate along the fibers via transverse Anderson localization. We made the first observation of transverse Anderson localization in a natural fiber and further demonstrated light focusing and image transport in the fibers. This discovery opens up the possibility to use wild silk fibers as a biocompatible and bioresorbable material for transporting optical signals and images. Drawing inspirations from these discoveries, we designed and developed high-throughput fabrication processes to create coatings and fibers with passive radiative-cooling properties. The radiative-cooling coatings consist of various nanoparticles imbedded within a silicone thin film. The sizes and materials of the nanoparticles were chosen to provide simultaneously high solar reflectivity and thermal emissivity. The coating has been implemented in two site studies on real roofs and has demonstrated reduced roof temperature by up to 30oC in the summer and associated reduction of electricity usage by up to 30%. We also made biomimetic fibers from regenerated silk fibroin and a thermoplastic using wet spinning. Spectroscopic measurements showed that these man-made fibers exhibit exceptional optical properties for radiative-cooling applications.

This research addresses challenges in two major applications, both related to photonic cognitive sensing. The first part, “Implantable Photonic Nano-Probe Detectors for Neural Imaging”, focuses on imaging system in the neural sciences field. The second part, “Advanced Control System for Optical Data Communications”, covers embedded low power control systems for optical communications. Implantable Photonic Nano-Probe Detectors for Neural Imaging This first part address the problem of simultaneous and real-time monitoring of dense brain neural activity, with the capability of cellular resolution and cell-type specificity included. For decades, electrophysiology has been the “gold standard” for the recording of neural activity. Despite recent advances, electrophysiology techniques can typically monitor fewer than 100 neurons simultaneously, due to the practical limits of electrode density. Additionally, the ability of direct monitoring specific cell types is not possible here. With the introduction of a growing panel of fluorescent optical reporters for brain function mapping, optical microscopy techniques have demonstrated the ability to track the activity of hundreds of neurons simultaneously in a much less invasive manner but with high spatial resolution, low-to-moderate temporal resolution and cell-type specificity. Unfortunately, only superficial layers of the brain can be imaged by free-space microscopy, due to the intrinsic light scattering and absorption limitation in brain tissue. To allow optical fluorescence imaging of deeper layers of the brain with proper a signal-to-noise ratio, a dense and scalable 3-D lattice of photo emitter and detector pixels (E-Pixels and D-Pixels, respectively) must be distributed on shanks for possible insertion into the brain. The 3-D lattice (combined fluorescent optical reporters) is expected to give an activity image of a very large neural population at an arbitrary depth in the brain. This work presents the design and implementation of the aforementioned 3-D photo- detectors (D-Pixels), associated with data processing and readout circuitries, for the future assembly of a probe-based system for functional imaging of neural activity. One of the main challenges of producing a probed-based version of a fluorescence microscope is the rejection of the light used to excite the fluorescent reporters. This is commonly done in the spectral domain with band-pass filters for free-space microscopy. However, these filters are not implementable with the proper optical density at the probe scale. The probe-based photo-detectors must be capable of rejecting the excitation light and capturing only the fluorescent response without the use of optical filters. Integrated Geiger-mode single-photon avalanche diodes (SPADs) are used as the sensing devices, which provide the ability to capture low fluorescence signals, fast response in the time domain, and direct digital readout. By engineering narrow E-Pixels angular-excitation fields and overlapping them with the narrow D-Pixels detection fields, fluorescent sources can be spatially localized. The detectors are embedded into four ultra-thin implantable shanks, associated with data processing units and readout circuits, all forming the photonic nano-probe detectors (also referred to as “D-Pixels Camera Chip (DCC)”). The shanks have dimensions of 110um×50um each, with 100 pixels along a shank (a total number of 400 pixels), distributed over 3mm length. The data generated by the photonic nano-probe detectors, is serially streamed out at a rate of 640Mbps, for offline analysis and image reconstruction. The photonic nano-probe detectors are fabricated in a conventional CMOS 0.13um technology. This part of the thesis first proposes and develops the architecture of the photonic nano-probe detectors. The challenges of designing high density, ultra-thin probes with the aforementioned form factor, fabricated in CMOS 0.13um technology is also discussed. Secondly, the design and implementation of testability and debugging options are mentioned, as playing an important role in achieving research goals. Last the design of lab experimental setups is presented and as well as the measurement results of the photonic nano-probe detectors. Experimental results indicate on achieving the crucial key features of the research work, the capability of rejecting the excitation light and capturing only the fluorescent decay response without the use of optical filters. Additionally, the results show that the photonic nano-probe detectors can precisely localize and map into a 2-D image, a light source within a pixel resolution.   Advanced Control System for Optical Data Communications The second part of the thesis focuses on the problem of initialization and temperature stabilization of silicon photonic (SiP) devices, with focus on dramatic power reduction of the power consumption. While microelectronics technology continues growing in scale, bandwidth, and integration of multiple systems on a single silicon die, the traditional electrical interconnects become the speed bottleneck in high-performance data communication systems. On the other hand, silicon photonics offers a promising platform for integration and manufacturing of photonics devices for high speed data transfer applications, such as access networks, supercomputers, chip-to-chip interconnects, and data centers. Additionally, the high index contrast of silicon platform and its compatibility with CMOS technologies, gives rise to integration of high speed, power efficient silicon photonic interconnects and most innovative CMOS technologies. Micro-ring resonators (MMRs), which are important building blocks is many silicon photonics applications, became attractive devices in many optical communication systems. This is due to their wavelength tuning ability, low power consumption and small footprint. However, temperature changes in their environment will shift their resonance from the desired point (due to high thermo-optical coupling in silicon), leading to performance degradation of the optical link. Compensating the degradation in performance can be directly translated to an excess in overall power consumption of the link, which will be critical in high-speed optical data communication systems. This work develops and demonstrates an ultra-low power control system, for initialization and temperature stabilization of MMRs. It utilizes an integrated heater, to thermally tune and lock the resonator to the desired wavelength. Traditional feedback loops rely on tapping a portion of the optical signal with the use of integrated photodiodes. They lock on the desired wavelength by sensing the maximum signal intensity, observed by the photodiode. The suggested control system in this work is based on an analog control system and utilizes the photo-conductance effect of doped-resistive heaters, to sense the optical power through the micro-ring. This part of the thesis first develops a VERILOG-A model for the photo-conductance effect of the doped-resistive heater. This enables the integration of the heater’s model with the proposed control circuits, into a circuit design simulator. Secondly, an architecture for the control system is proposed and developed, which includes fundamental electronic circuits with the aforementioned heater’s model. For the purpose of circuit level simulations, a design methodology is developed, which is based on semi-ideal models for the electronic building blocks. Then a circuit level simulator is used to simulate and evaluate the performance of the control system. Last, the proposed system is implemented with the use of commercial discrete electronic components, all connected on a custom designed printed circuit board (PCB). Simulations of the control system indicate an initialization time less than 160us, and maximum locking voltage error of 1.8%. The obtained dynamic energy consumption is ED=85 fJ/bit/oC for bit rate of 20Gbps. Though the control system is targeted for MRRs, it can be easily expanded to control other PIC devices.

The quantum description of light offers a unique set of optical effects that has led to promising applications beyond those described by classical physics. Although well-defined quantum states of light do not persist in typical classical environments, phenomena such as entanglement often enhance optical approaches to communication, measurement, and sensing. With the emergence of new tasks in classical and quantum optical technology, new tools are required that must be specifically engineered including the generation of quantum states. This thesis is concerned with three principle tasks in engineering and implementing entangled photonic states. First, the use of frequency anti-correlated and polarization entangled two-photon states generated during spontaneous parametric down conversion (SPDC) to precisely evaluate optical delays with quantum interferometry is demonstrated in a realistic commercially available optical telecommunication device. Second, the study of correlated orbital angular momentum (OAM) states for efficient object identification is presented. Finally, experimental efforts towards the development of sources for entangled weak coherent states are discussed. The generation of broadband entangled states leading to well-defined second order interference patterns is a necessary step for the application of low coherence quantum interferometry as a metrological device. The flexibility of non-uniformly chirped periodically poled nonlinear crystals offers a rich set of tools for precise state engineering. The experimental evaluation of a broadband source of polarization entanglement is presented. In addition, design considerations for applications that require optimized quantum interference features are discussed along with a numerical investigation of the limits of quantum interferometry with even order dispersion cancellation. We present an experimental demonstration of correlated OAM sensing exploiting the two-dimensional and correlated nature of states produced during SPDC projected onto the OAM basis. Efficient object recognition through the identification of azimuthal symmetries of arbitrary objects is achieved by observing the full two-photon joint OAM spectrum and focusing on non-conserved OAM components not found in the natural OAM spectrum of SPDC. Finally, quantum key distribution (QKD) is currently the most successful quantum optical application; however, a limiting trade off between the achievable rates and distances confines the approach to niche applications. The generation of entangled coherent states has been proposed to transition QKD into a new regime that would set aside single photons and two-photon entangled states for higher intensity coherent pulses. The key technical limitation that has prohibited the demonstration of such states is a reliable source of single-photon cross phase modulation. The plausibility and experimental efforts towards creating such an environment in a solid state device is presented.

Afin d’adresser la problématique liée aux limitations des interconnections métalliques en termes de débits notamment, la photonique Si s’est imposée comme une technologie de choix. Un des composants de base des circuits photonique Si est le photodétecteur : Il permet de convertir un signal optique en signal électrique. Les photodétecteurs à base de Ge sur Si ont montré leur potentiel et offrent la meilleure alternative aux photodétecteurs III-V, pour une intégration dans les circuits photoniques Si.Dans ce contexte, les photodiodes à base de Ge su Si ont été étudiées. L’optimisation des photodiodes p-i-n a permis l’obtention de résultats à l’état de l’art. Une nouvelle approche utilisant une double hétéro-jonction latérale Si/Ge/Si a été proposée afin d’augmenter la responsivité mais aussi afin de proposer une meilleure solution d’intégration, avec les modulateurs Si notamment. Pour augmenter encore la sensibilité des récepteurs, l’utilisation de photodiodes à avalanche est cependant nécessaire. La structure SACM (Separate Absorption Charge Multiplication), combinant le faible bruit de multiplication du Si et l’absorption du Ge aux longueurs d’onde télécom, a d’abord été étudiée. Des modèles ont été développées afin d’optimiser le fonctionnement, et ces photodiodes ont été fabriquées et caractérisées. Les résultats obtenus sur des photodiodes éclairées par la surface (produit Gain-Bande passante de 560GHz à seulement -11V) sont très encourageant pour une intégration avec un guide d’onde. D’autre part, les photodiodes p-i-n en Ge sur Si, ont été étudiées en avalanche. La faible largeur de la zone intrinsèque a permis de diminuer le bruit de multiplication par effet « dead space », et le fonctionnement à 10Gbits/s pour un gain de 20 et une puissance optique de seulement -26dBm, pour une tension de -7V, sans utilisation d’amplificateur (TIA), a pu être démontré. Ces développements ouvrent ainsi la voie vers des récepteurs rapides, à faible consommation électrique et grande sensibilité. / To address the issue related to the limitations of metallic interconnects especially in terms of bitrate, Si photonics has become the technology of choice. One of the basic components of photonic circuits is the photodetector: It allows to convert an optical signal into an electrical signal. Photodetectors based on Ge on Si have shown their potential and offer the best alternative to III-V photodetectors, for integration into Si photonic circuits. In this context, the Ge on Si photodiodes have been studied. The optimization of pin photodiodes enabled the achievement of state of the art results. A new approach using a double lateral Si/Ge/Si heterojunction was proposed to increase the responsivity but also to provide a better integration solution, especially with Si modulators. To further increase the sensitivity of the receivers, the use of avalanche photodiodes, is however necessary. SACM (Separate Absorption Charge Multiplication) structure, combining Si low multiplication noise and Ge absorption at telecom wavelengths was first studied. Models have been developed to optimize the devices, and the photodiodes have been fabricated and characterized. The results obtained on the surface illuminated photodiodes (Gain-bandwidth product of 560GHz only -11V) are very encouraging for waveguide integration. On the other hand, Ge on Si pin photodiodes have been studied in avalanche. The small width of the intrinsic region contributed to the multiplication noise reduction thanks to "dead space" effect, and operation at 10Gbps for a gain of 20 and an optical power of -26dBm at only-7V, without using amplifier (TIA), have been demonstrated. These developments open the way to fast, low power consumption and high sensitivity receivers.

An apodized grating coupler with the best coupling efficiency hitherto reported for shallow-etched waveguide grating couplers is described. By appropriate choice of waveguide/grating thicknesses and varying the coupling strength of the grating coupler via tailoring its fill factor to optimize the mode matching, a coupling loss of only 1.2dB was obtained for each fiber/silicon waveguide interface with a slightly titled optical fiber. / Photonic integrated circuits (PICs) based on Silicon-on-insulator (SOI) substrate were proposed to make miniaturized photonic devices on chip, so that low-cost and compact devices for applications including sensing, inter/intra-chip communications and optical fiber communications could be made. One of the key challenges in the development of highly integrated PICs is efficient coupling of light between a submicron-sized nanophotonic wire and an optical fiber due to the large loss inherent from the mismatch in mode field size between the optical fibers and the nanophotonic wire waveguides. An attractive approach for efficient coupling is to use diffractive grating couplers which show many advantages over alternative approaches. However the angled alignment of the optical fiber to the grating as reported in the previous work is not desirable for a low-cost optical packaging process. / The 2D grating couplers could be used as polarization splitter. Polarization insensitive coupling and polarization-diversity circuits are realized by the 2D grating couplers. We also demonstrated a novel silicon waveguide grating which serves dual functions: as a 1x2 variable integrated beam splitter/combiner and as an out-of plane diffractive element for coupling light. The split ratio can be tuned by changing the launch position of the optical fiber without introducing much excess loss. An integrated Mach-Zehnder interferometer (MZI) is implemented with this novel functional element. This MZI was demonstrated as a demodulator for differential phase-shift-keying (DPSK) signal. / We demonstrated a simple technique to realize vertical fiber coupling with linearly chirped grating periods. No additional fabrication process is required yet a comparable coupling efficiency is achieved with the proposed chirped grating couplers with vertical optical fibers. Design and experimental results of onedimensional (lD) gratings, two-dimensional (2D) gratings, focusing gratings and fully-etched nanoholes gratings are described in the thesis. We also describe the waveguides and grating couplers fabricated on silicon-on-sapphire for mid-infrared applications. / Chen, Xia. / Adviser: H.K. Tsang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Ultrawideband (UWB) technology has received considerable attention in recent years as it is regarded to be able to revolutionise a wide range of applications. UWB imaging for breast cancer detection is particularly promising due to its appealing capabilities and advantages over existing techniques, which can serve as an early-stage screening tool, thereby saving millions of lives. Although a lot of progress has been made, several challenges still need to be overcome before it can be applied in practice. These challenges include accurate signal propagation modelling and breast phantom construction, artefact resistant imaging algorithms in realistic breast models, and low-complexity implementations. Under this context, novel solutions are proposed in this thesis to address these key bottlenecks. The thesis first proposes a versatile electromagnetic computational engine (VECE) for simulating the interaction between UWB signals and breast tissues. VECE provides the first implementation of its kind combining auxiliary differential equations (ADE) and convolutional perfectly matched layer (CPML) for describing Debye dispersive medium, and truncating computational domain, respectively. High accuracy and improved computational and memory storage efficiency are offered by VECE, which are validated via extensive analysis and simulations. VECE integrates the state-of-the-art realistic breast phantoms, enabling the modelling of signal propagation and evaluation of imaging algorithms. To mitigate the severe interference of artefacts in UWB breast cancer imaging, a robust and artefact resistant (RAR) algorithm based on neighbourhood pairwise correlation is proposed. RAR is fully investigated and evaluated in a variety of scenarios, and compared with four well-known algorithms. It has been shown to achieve improved tumour detection and robust artefact resistance over its counterparts in most cases, while maintaining high computational efficiency. Simulated tumours in both homogeneous and heterogeneous breast phantoms with mild to moderate densities, combined with an entropy-based artefact removal algorithm, are successfully identified and localised. To further improve the performance of algorithms, diverse and dynamic correlation weighting factors are investigated. Two new algorithms, local coherence exploration (LCE) and dynamic neighbourhood pairwise correlation (DNPC), are presented, which offer improved clutter suppression and image resolution. Moreover, a multiple spatial diversity (MSD) algorithm, which explores and exploits the richness of signals among different transmitter and receiver pairs, is proposed. It is shown to achieve enhanced tumour detection even in severely dense breasts. Finally, two accelerated image reconstruction mechanisms referred to as redundancy elimination (RE) and annulus predication (AP) are proposed. RE removes a huge number of repetitive operations, whereas AP employs a novel annulus prediction to calculate millions of time delays in a highly efficient batch mode. Their efficacy is demonstrated by extensive analysis and simulations. Compared with the non-accelerated method, RE increases the computation speed by two-fold without any performance loss, whereas AP can be 45 times faster with negligible performance degradation.