表面電漿是由貴金屬表面電荷密度漲落引起的沿著金屬表面傳播的電磁波。在過去十年裡，表面電漿效應因其在光子器件，傳感，表面增強螢光，尤其是表面增強拉曼散射(SERS) 方面的應用而引起了廣泛的關注.許多著作中的結論已經證實了的預期的SERS 強度，因此使得基於各種不同納米結構中的熱點的SERS變成一種下一代超敏感生物傳感平臺。因為表面電漿的波長和材料介電性質密切相闕，受f於此，難以進一步減小，所以對於進一步的各種應用來說，保證產生高強度的表面電漿使至關重要。同時，用電漿實現納米光子器件已經引起了研完者長久的興趣。例如，基於等問距規則排列的密置金屬納米顆粒之間突破衍射極限的的近場耕合已經被用於傳輸光信號。但是，輻射和吸收損耗在此類波導中是很嚴重的。因此，設計新概念的電漿器件是急需的。 / 有鑒於上述種種問題，本論文集中于總結構和材料兩方面剪裁表面電漿以期達到下面的要點和目的: / (1)基於傳播電漿(PSPs) ，或者傳播電漿同局域電漿(LPRs) 的結合而發展新的簡單的器件，由此提供顯著的聚焦、電磁場和場強增強。這種器件可以應用於很多方面，包括依賴強場的生物分子傳感探測，以及非線性光學效應。 / (2) 設計基於增益介臂的低損耗的納米光子學器件，這種器件能夠為納米光子器件提供切實的可行性。針對表面電漿共振和電漿結構植于的介電環境之間聯繫，獲得其理論闡釋。這一工作將可以為傳感和器件設計提供深入的理解。 / 本論文中我們已經得到了如下的成果: / (1)一種基於將表面電漿聚焦到金屬盤中心孔而實現級聯放大增強的SERS 激勵源被提出和理論研究。這種器件提供了準均勻，水平偏振，較大面積的強SERS 激勵源。如時域有限差分(FDTD) 方法所揭試，強度譜線和波長範圍在650-1000 nm的近場性質展混出了一系列增強模式。在最佳的增強模式下，孔洞中的電場可以使得SERS 信號獲得四次方的進一步增強。同時一種解析模型也被提出來給FDTD結果以精確的解釋。我們的模型同時揭示了通過侵化金屬盤尺度而得到八次方場增強的可能性。我們的結果表明極強的電場增強，並且聚焦的電場是平行于金屬盤平面的效果，只能在中間包含一個孔洞的中空金屬盤(HMDs) 中才可能實現。這是因為金屬盤中間絶悸的問時的存在使得孔洞邊棒的電子不能流通間隙，進進而使得高強度的電場可以存在。另一方面，在實心的金屬盤的情形下，電子流會傾向於抑制到達中心的表面電漿的強度。除了產生高度優化的SERS 熱點，這種大面積的活性孔洞在螢光增強和非線性光學中也提供了一些潛在的應用。 / 除了中空金屬盤，基於經由增孟輔助下PSPs 的LPRs 之間的衍射共掠，我們開發了另一種一種高度侵化的熱點。由此得到的器件被理論上分析。衍射共振的過程是經由下述過程實現的:由LPRs 實現的光場局域化， LPRs 和PSPs 相互作用，以及通過PSPs 的能量傳遞。我們的研究表明通過給PSPs 引入光學增孟，可以從一種激光過程中的到LPRs 非常強的電磁場增強。我們發現通過現實的增豆豆水平，局域電場的增強引子可以達到10⁷。因此，我們為實現依賴強電場的單分子SERS提供了一種理想的方案，並且這種方案也是一種納米激光的新機制。 / (2) 基於增孟輔助的電漿共振金屬納米顆粒鏈，我們提出了一種低損耗納米尺度的波導。我們證明通過引入增孟材料或者引入適當的介電材料作為周圍環境，波導的損耗可以顯著減小。為了得到低損耗傳翰的復介電譜，我們開發了一種高效的膺正交基展開(POBE) 方法。本徵模式分析揭示了低損耗模式的物理源頭，同時給出了除了基於單體偶極共振傳輸之外能量傳輸的可能性。我們提出一種基於電子書刻蝕和化學合成納米顆粒的一種製備方案。這種電漿波導可以構成納米光學器件的基石，尤其是用於集成納米光子學線路。同時，我們原創的揭示表面電漿的物理機理的POBE 方法可以用於進一步研究優化增豆豆輔助的電漿結構，進而設計良好的納米光子器件。 / 本論文始於一個古老問題:宏觀尺度下基於傳統介電材料光聚焦和傳導，并最後終結於納米尺度內經由增益材料和電漿結構的表面電漿的聚焦、和引導。論文結尾，本文給出了展望以及幾種可能的器件實現方案。 / Surface plasmons (SPs) are electromagnetic waves that propagate along the surface of a noble metal via fluctuations in electron density. In the last decade, SPs effects gained widespread attention for their potential application in photonic devices, sensing, surface-enhanced fluorescence, especially Surface-Enhanced Raman Scattering (SERS). Many published results have confirmed the expected strengths of SERS, hence making it possible for SERS to become a next generation ultra-sensitive biosensing platform, which may take the form of various nano-structures in order to achieve optimized hot spots. While the wavelength of SPs is closely related to material dielectric properties and has limited scope for further reduction, it is of critical importance to ensure that SPs are being generated with the highest intensity before any further application advancement is possible. Meanwhile, plasmonics has aroused longstanding interests among researchers to realize nanophotonic devices. For example, ordered arrays of closely spaced metallic nanoparticles (MNP) have been employed to transport optical signals via near-field coupling below the diffraction limit. However, radiation and absorption losses in these waveguides can be serious. New concepts for novel plasmonic devices are essential. / In light of these issues, this thesis focuses on tailoring SPs from the viewpoints of structural and material properties with the following objectives: / (1) To develop a new class of simple plasmonic devices based on tailoring of propagating surface plasmons (PSPs) or cooperation between PSPs and localized plasmon resonance (LPRs) to offer significant field focusing and intensity enhancement. It can serve a wide range of applications, including high field related biomolecular sensing and detection as well as non-linear optical effects. / (2) To design low loss nanophotonic wave guides based on gain medium, which may offer real opportunity for practical nanophotonic devices. To obtain a theoretical interpretation of relationship between surface plasmon resonance and host environment where the plasmonic structure embedded. This study should provide further insight towards sensing and device design. / We have achieved the following results in this project: / (1) A novel SERS excitation source based on focusing of surface plasmons around the center hole of a metal disk for cascaded enhancement is put forward and studied theoretically. The device offers intense SERS excitation with quasi-uniformity and horizontal polarization over a comparatively large hole. As revealed by fmite-difference time-domain (FDTD) method, the intensity spectra and the characteristics of the near field for the wavelength range of 650-1 000 nm exhibit a number of enhancement modes. Electric field intensity of the optimal mode enhances the SERS signal inside the hole by over four orders. An analytical model was also developed to gain precise interpretation on FDTD results. Our model also reveals the possibility of achieving eight orders of enhancement by optimizing the scale of the disk. Our results indicate that much higher electric field enhancement in hollow metal disks (HMDs) can only be possible when we have a hole at the centre and the direction of the focusing field is parallel to the surface of the plasmonic device. This is because of the presence of an insulating gap at the center, that higher level of electric field can exist as electrons are not allowed to flow pass the gap. On the other hand, in the case of a solid metal disk, the flow of mobile electron will tend to dampen the amplitude of the arriving SPs. In addition to generation of highly optimized hot spots for SERS, the large active hole also offers potential applications in fluorescence enhancement and nonlinear spectroscopy. / In addition to HMDs, we also develop a kind of highly optimized hot spots based on diffraction coupling between LPRs via gain-assisted PSPs. Thus derived device was theoretically analyzed. The process of diffraction coupling is achieved via localization of light by LPRs, LPRs-PSPs interplay and PSPs transfer. Our study shows that by incorporating optical gain to PSPs, a very strong boost of the electromagnetic enhancement of LPRs can be expected from a lasing process. We find that with a practical gain level, the enhancement factor of local electric field intensity can be larger than 10⁷. Hence, we offer an ideal configuration to realize high-field dependent single molecule SERS and also a newly applied physical scheme for nano-Iaser. / (2) We propose a low-loss nanoscale wave guide based on gain-assisted plasmonic resonance MNP chain. We demonstrate that by employing a gain material or even an appropriate dielectric for the host environment, waveguide loss can be reduced dramatically. A highly efficient pseudo-orthonormal basis expansion (POBE) method for obtaining the complex dielectric spectra of the low-loss transmission has been developed. Eigenmode analysis revealed the physical origin of those low-loss wave guiding modes, which opens the possibility to achieve waveguiding other than using conventional dipolar resonances of individual particles. A scheme based on electron beam lithography and chemically synthesized nanoparticles has been proposed to fabricate the device. Such plasmonic waveguides may serve as building blocks for making nanoscale optical devices especially for integrated nanophotonic circuits. Meanwhile, the originally developed POBE method, which reveals the general physical mechanism of SPs, can be used to further explore optimized gain-assisted plasmonic structures to design favorable nanophotonic devices. / This thesis begins with an old problem: light focusing and guiding in macroscopic scale with traditional dielectric, and sum up finally with SPs focusing and guiding in nanoscale with gain material and plasmonic material. An outlook is presented at last with several potential schemes for the device realization. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Haixi. / "September 2011." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 124-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chapter Chapter1 --- Introduction --- p.1 / Chapter 1.1 --- Towards field intensity focusing and guiding of electromagnetic wave --- p.1 / Chapter 1.2 --- Surface plasmons as a route to realize electromagnetic field focusing and waveguiding in nanoscale --- p.3 / Chapter 1.3 --- Structure of this thesis --- p.10 / Chapter Chapter2 --- Plasmonic near field engineering: structural and material aspects --- p.13 / Chapter 2.1 --- Light focusing using near field oflocalized plasmon resonances --- p.13 / Chapter 2.2 --- Plasmonic near field focusing through propagating surface plasmons --- p.30 / Chapter 2.3 --- Various schemes for near field focusing through surface plasmons --- p.33 / Chapter 2.4 --- Guiding surface plasmons in nanoscale --- p.35 / Chapter 2.5 --- Gain-assisted surface plasmons: a different path to field enhancement and guiding --- p.38 / Chapter Chapter3 --- Surface plasmons: characteristics and methodology --- p.42 / Chapter 3.1 --- Characteristics of localized plasmon resonance --- p.42 / Chapter 3.2 --- Localized plasmon resonance: Mie theory and its variations --- p.44 / Chapter 3.3 --- Characteristics of propagating surface plasmons --- p.49 / Chapter 3.4 --- Reflection Pole Method for studying propagating surface plasmons in multilayer structures --- p.55 / Chapter 3.5 --- Pseudo-orthonormal basis expansion method: a new mathematical scheme for modeling surface plasmons --- p.58 / Chapter Chapter4 --- High field generation through intensity focusing of propagating surface plasmons --- p.62 / Chapter 4.1 --- Introduction --- p.62 / Chapter 4.2 --- The hollow metal disk design and its characteristics --- p.64 / Chapter 4.3 --- Quasi-uniform excitation source based on focusing of propagating surface plasmons for cascade enhancement of surface enhanced Raman scattering --- p.68 / Chapter 4.4 --- Conclusions and outlook --- p.78 / Chapter Chapter5 --- High field generation through intensity enhancement of localized plasmon resonance from gain-assisted diffraction coupling --- p.81 / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Diffraction excitation of localized plasmon resonance from propagating surface plasmons --- p.83 / Chapter 5.3 --- Diffraction coupling of localized plasmon resonance through gain-assisted propagating surface plasmons --- p.89 / Chapter Chapter6 --- Gain-assisted plasmonic waveguides based on nanoparticle chains: an effective device approach for achieving low loss in nanoscale dimensions --- p.97 / Chapter 6.1 --- Introduction --- p.97 / Chapter 6.2 --- Theoretical study of near-field particle interactions in active plasmon wave guides --- p.99 / Chapter 6.3 --- Routing and splitting of electromagnetic energy in nanosphere plasmon waveguides --- p.103 / Chapter 6.4 --- Conclusions --- p.107 / Chapter Chapter7 --- Conclusions and outlook --- p.109 / Appendix --- p.117 / Bibliography --- p.124

Metasurfaces, a new class of artificial media attracting great research interest, are composed of a two-dimensional ensemble of designer optical antennas arranged with subwavelength separation that introduce spatially-varying optical properties (e.g., amplitude, phase and polarization). By engineering the subwavelength optical antennas and integrating with functional materials, metasurfaces can manipulate light at one’s will and have led to the demonstration of many exotic electromagnetic phenomena. Metasurfaces have the potential to replace bulky optical components and devices as they are ultra-thin (subwavelength thickness), light weight, and able to provide new functionalities and overcome the limitations of their conventional counterparts. There are a number of promising areas in fundamental research and practical applications where metasurfaces could have a significant impact. In this dissertation, I studied the fundamental physics of the strong interaction between light and metasurfaces and explored passive and active nanophotonic devices based on metasurfaces. I demonstrated metasurface-based devices showing record-breaking or completely novel functionalities; these devices include optical modulators for dynamic control of light propagating in free space over an unprecedented broad wavelength range, photonic integrated devices with record-small footprints, and metasurface sensors orders of magnitude more sensitive than the state-of-art sensing techniques. Strongly correlated perovskites possess widely tunable electronic structure that can host a variety of phases. Nickelates, in particular, undergo electric-field-tunable phase transitions with dramatic changes in the optical properties. In Chapter 2, I will describe my discovery of a new optical phase-transition material SmNiO3 and experimental demonstration of strong optical modulation utilizing the large and non-volatile optical refractive index change associated with electron-doping induced phase transition of SmNiO3. Large electrical modulation of light over a broad wavelength range, from the visible to the mid-infrared,  = 0.4 m – 17 m, is demonstrated using thin-film SmNiO3. By integrating SmNiO3 and plasmonic metasurface structures, modulation of a narrow band of light that resonantly interacts with the metasurfaces is realized. Furthermore, solid-state electro-optic modulators are demonstrated by integrating SmNiO3 and solid polymer electrolytes. Correlated perovskites with tunable and non-volatile electronic phases create a new platform for active photonic devices, such as optoelectronic modulators, electrically programmable optical memories, smart windows, and variable emissivity coatings. Research on metasurfaces has so far focused on controlling wavefronts of light propagating in free space, and the implication of metasurfaces on integrated photonics has not been explored. I conducted initial work on using metasurfaces to control light propagation on a chip. In chapter 3, I will show that gradient metasurface structures consisting of phased arrays of plasmonic or dielectric nano-antennas provide a platform to control guided waves via strong optical scattering at subwavelength intervals. Such gradient metasurfaces enable the creation of small-footprint, broadband, and low-loss photonic integrated devices. I will describe experimental demonstration of waveguide mode converters, polarization rotators, and asymmetric optical power transmission in waveguides patterned with plasmonic gradient metasurfaces. I will also describe experimental demonstration of all-dielectric on-chip polarization rotators that are based on phased arrays of Mie resonators and have negligible insertion losses. Metasurfaces emerge as a new promising photonic platform for biosensing because they offer strong optical confinement and tunable optical resonances. In chapter 4, I will show that metasurface-based biosensors consisting of gold nano-antenna arrays loaded with graphene and working in the mid-infrared spectral range can achieve simultaneous high-sensitivity and high-specificity detection of biomolecules. The biosensors support a hybrid plasmon-phonon resonant mode that concentrates incident light into deeply subwavelength optical spots with local light intensity enhancement by a factor of 104. Strong light-molecule interactions in these optical spots allow for determing protein molecule concentrations via spectral shifts of the plasmon-phonon resonance. A combination of passive and active tuning of the metasurface sensors allows for spectrally overlapping the plasmon-phonon resonance and the vibrational modes of protein molecules, so that I can identify protein molecules via their characteristic mid-infrared “fingerprints”. The high sensitivity and specificity of the metasurface sensors enable the detection of the secondary structure of protein immunoglobulin (IgG) molecules with a sensitivity four orders of magnitude higher than that of conventional attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR).

The progressive blooming of silicon photonics technology (SiP) has indicated that optical interconnects may substitute the electrical wires for data movement over short distances in the future. Silicon Photonics platform has been the subject of intensive research for more than a decade now and its prospects continue to emerge as it enjoys the maturity of CMOS manufacturing industry. SiP foundries all over the world and particularly in the US (AIM Photonics) have been developing reliable photonic design kits (PDKs) that include fundamental SiP building blocks such as wavelength selective modulators and tunable filters. Microring resonators (MRR) are hailed as the most compact devices that can perform both modulation and demodulation in a wavelength division multiplexed (WDM) transceiver design. Although the use of WDM can reduce the number of fibers carrying data, it also makes the design of transceivers challenging. It is probably acceptable to achieve compactness at the expense of somewhat higher transceiver cost and power consumption. Nevertheless, these two metrics should remain close to their roadmap values for Datacom applications. An increase of an order of magnitude is clearly not acceptable. For example costs relative to bandwidth for an optical link in a data center interconnect will have to decrease from the current $5/Gbps down to <$1/Gbps. Additionally, the transceiver itself must remain compact. The optical properties of SiP devices are subject to various design considerations, operation conditions, and optimization procedures. In this thesis, the general goal is to develop mathematical models that can accurately describe the thermo-optical and electro-optical behavior of individual SiP devices and then use these models to perform optimization on the parameters of such devices to maximize the capabilities of photonic links or photonic switch fabrics for datacom applications. In Chapter 1, Introduction, we first provide an overview of the current state of the optical transceivers for data centers and datacom applications. Four main categories for optical interfaces (Pluggable transceivers, On-board optics, Co-packaged optics, monolithic integration) are briefly discussed. The structure of a silicon photonic link is also briefly introduced. Then the direction is shifted towards optical switching technologies where various technologies such as free space MEMS, liquid crystal on silicon (LCOS), SOA-based switches, and silicon-based switches are explored. In Chapter 2, Silicon Photonic Waveguides, we present an extensive study of the silicon-on-insulator (SOI) waveguides that are the basic building blocks of all of the SiP devices. The dispersion of Si and SiO2 is modeled with Sellmiere equation for the wavelength range 1500–1600 nm and then is used to calculate the TE and TM modes of a 2D slab waveguide. There are two reasons that 2D waveguides are studied: first, the modes of these waveguides have closed form solutions and the modes of 3D waveguides can be approximated from 2D waveguides based on the effective index method. Second, when the coupling of waveguides is studied and the concept of curvature function of coupling is developed, the coupled modes of 2D waveguides are used to show that this approach has some inherent small error due to the discretization of the nonuniform coupling. This chapter finishes by describing the coefficients of the sensitivity of optical modes of the waveguides to the geometrical and material parameters. Perturbation theory is briefly presented as a way to analytically examine the impact of small perturbations on the effective index of the modes. In Chapter 3, Compact Modeling Approach, the concept of scattering matrix of a multi-port silicon photonic device is presented. The elements of the S-matrix are complex numbers that relate the amplitude and phase relationships of the optical models in the input and output ports. Based on the scattering matrix modeling of silicon photonics devices, two methods of solving photonic circuits are developed: the first one is based on the iteration for linear circuits. The second approach is based on the construction of an equivalent signal flow graph (SFG) for the circuit. We show that the SFG approach is very efficient for circuits involving microring resonator structures. Not only SFG can provide the solution for the transmission, it also provides the signal paths and the closed-form solution based on the Mason’s graph formula. We also show how the SFG method can be utilized to formulate the backscattering effects inside a ring resonator. In Chapter 4, Scalability of Silicon Photonic Switch Fabrics, we develop the models for electro-optic Mach-Zehnder switch elements (2×2). For the electro-optic properties, the empirical Soref’s equations are used to characterize how the loss and index of silicon changes when the charge carrier density is changed. We then use our photonic circuit solver based on the iteration method to find accurate result of light propagation in large-scale switch topologies (e.g. 4×4, and 8×8). The concept of advanced path mapping based on physical layer evaluation of the switch fabric is introduced and used to develop the optimum routing tables for 4×4 and 8×8 Benes switch topologies. In Chapter 5, Design space of Microring Resonators, we introduce the concept of curvature function of coupling to mathematically characterize the coupling coefficient of a ring resonator to a waveguide as a function of the geometrical parameters (ring radius, coupling gap, width and height of waveguides) and the wavelength. Extensive 2D and 3D FDTD simulations are carried out to validate our modeling approach. Experimental demonstrations are also used to not only further validate our modeling of coupling, but also to extract an empirical power-law model for the bending loss of the ring resonators as a function the radius. By combining these models, we for the first time present a full characterization of the design space of microring resonators. Moreover, the value of this discussion will be further apparent when the scalability of a silicon photonic link is studied. We will show that the FSR of the rings determines the optical bandwidth but it also impacts the properties of the ring resonators. In Chapter 6, Thermo-optic Efficiency of Microheaters, we develop analytical models for the thermo-optic properties of SiP waveguides. For the thermo-optic properties, the concept of thermal impulse response is mathematically developed for integrated micro-heaters. The thermal impulse response is a key function that determines the tradeoff between heating efficiency and heating speed (thermal bandwidth), as well as allows us to predict the pulse-width-modulation (PWM) optical response of the heater-waveguide system. One of the motivations behind this study was to find the highest possible efficiency for thermal tuning of microring resonators to use it in the evaluation of the energy consumption of a photonic link. The results indicate 2 nm/mW which is in agreement with the trends that we see in the literature. In Chapter 7, Crosstalk Penalty, we theoretically and experimentally investigate the optical crosstalk effects in microring-based silicon photonic interconnects. Both inter-channel crosstalk and intra-channel crosstalk are investigated and approximate equations are developed for their corresponding power penalties. Inclusion of the inter-channel crosstalk is an important part of our final analysis of a silicon photonic link. In Chapter 8, Scalability of Silicon Photonic Links, we present the analysis of a WDM silicon photonics point-to-point link based on microring modulators and microring wavelength filters. Our approach is based on the power penalty analysis of non-return-to-zero (NRZ) signals and Gaussian noise statistics. All the necessary equations for the optical power penalty calculations are presented for microring modulators and filters. The first part of the analysis is based on various ideal assumptions which lead to a maximum capacity of 2.1 Tb/s for the link. The second part of the analysis is carried out with more realistic assumptions on the photonic elements in the link, culminating in a maximum throughput of 800 Gb/s. We also provide estimations of the energy/bit metric of such links based on the optimized models of electronic circuits in 65 nm CMOS technology.

A spatial domain Optimal Trade-off Maximum Average Correlation Height (SPOT-MACH) filter is proposed in this thesis. The proposed technique uses a pre-defined fixed size kernel rather than using estimation techniques. The spatial domain implementation of OT-MACH offers the advantage that it does not have shift invariance imposed on it as the kernel can be modified depending upon its position within the input image. This allows normalization of the kernel and allows inclusion of a space domain non-linearity to improve performance. The proposed SPOT-MACH filter can be used to maximize the height of the correlation peak in the presence of distortions of the training object and provide resistance to background clutter. One of the major characteristics of the SPOT-MACH filter is that it can be tuned to maximize the height and sharpness of the correlation peak by using trade-offs between distortion tolerance, peak sharpness and the ability to suppress clutter noise. A number of non-parametric local regression techniques offer a simplified approach to pattern recognition problems which employ linear filtering using low pass filters designed using moving window local approximations. In most of these cases the algorithms search for a region of interest near the point of estimation for various prevailing conditions which fit the required criteria. These estimates are calculated for a defined window size which is determined as being the largest area within which the estimators do not widely vary from the criteria. The only drawback in this approach is that the window size is directly proportional to the required computational resources and would adversely affect the performance of the system if the moving window size is not proportionate to the resources. The proposed filter employs an optimization technique using low-pass filtering to highlight the potential region of interests in the image and then restricts the movement of the kernel to these regions to allow target identification and to use less computational resources. Also another optimization technique is also proposed which is based on an entropy filter which measures the degree of randomness between two changing scenes and would return the area where change has occurred i.e. the target object might be present. This approach gives a more accurate region of interest than the low-pass filtering approach. Apart from the software based optimization approaches two hardware based enhancement techniques have also been proposed in this thesis. One of the approaches employs Field Programmable Gate Array (FPGA) to perform correlation process employing the inbuilt multipliers and look up tables and the other one uses Graphical Processing Unit (GPU) to do parallel processing of the input scene. Also in this thesis a detailed analysis of SPOT-MACH has been carried out by comparing with popular feature based techniques like Scale Invariant Feature Transform (SIFT) and a comparison matrix has been created. The proposed filter uses a two-staged approach using speed optimizations and then detection of targets from input scenes. Both visible and Forward Looking Infrared (FLIR) imagery data sets have been used to test the performance of filter.

Efficient tracking of deformable objects moving with variable velocities is an important current research problem. In this thesis a robust tracking model is proposed for the automatic detection, recognition and tracking of target objects which are subject to variable orientations and velocities and are viewed under variable ambient lighting conditions. The tracking model can be applied to efficiently track fast moving vehicles and other objects in various complex scenarios. The tracking model is evaluated on both colour visible band and infra-red band video sequences acquired from the air by the Sussex police helicopter and other collaborators. The observations made validate the improved performance of the model over existing methods. The thesis is divided in three major sections. The first section details the development of an enhanced active contour for object segmentation. The second section describes an implementation of a global active contour orientation model. The third section describes the tracking model and assesses it performance on the aerial video sequences. In the first part of the thesis an enhanced active contour snake model using the difference of Gaussian (DoG) filter is reported and discussed in detail. An acquisition method based on the enhanced active contour method developed that can assist the proposed tracking system is tested. The active contour model is further enhanced by the use of a disambiguation framework designed to assist multiple object segmentation which is used to demonstrate that the enhanced active contour model can be used for robust multiple object segmentation and tracking. The active contour model developed not only facilitates the efficient update of the tracking filter but also decreases the latency involved in tracking targets in real-time. As far as computational effort is concerned, the active contour model presented improves the computational cost by 85% compared to existing active contour models. The second part of the thesis introduces the global active contour orientation (GACO) technique for statistical measurement of contoured object orientation. It is an overall object orientation measurement method which uses the proposed active contour model along with statistical measurement techniques. The use of the GACO technique, incorporating the active contour model, to measure object orientation angle is discussed in detail. A real-time door surveillance application based on the GACO technique is developed and evaluated on the i-LIDS door surveillance dataset provided by the UK Home Office. The performance results demonstrate the use of GACO to evaluate the door surveillance dataset gives a success rate of 92%. Finally, a combined approach involving the proposed active contour model and an optimal trade-off maximum average correlation height (OT-MACH) filter for tracking is presented. The implementation of methods for controlling the area of support of the OT-MACH filter is discussed in detail. The proposed active contour method as the area of support for the OT-MACH filter is shown to significantly improve the performance of the OT-MACH filter's ability to track vehicles moving within highly cluttered visible and infra-red band video sequences.

Microresonators have the ability of strongly enhancing the propagating optical field, enabling nonlinear phenomena, such as bi-stability, self-pulsing and chaotic regimes, at very low powers. It is fundamental to comprehend the mechanisms that generate such dynamics, which are crucial for micro-cavities-based applications in communications, sensing and metrology. The aim of this work is to develop a scheme for the control of nonlinear regimes in microresonators, assuming the interplay between the ultra-fast Kerr effect and a slow intensity-dependent nonlinearity, such as thermo-optical effect. The framework of the coupled-mode theory is applied to model the system, while the bifurcation theory is used to investigate a configuration in which the power and frequency of a weak signal can control the behaviour of a strong pump. In this regards, this study demonstrates that the effect of a parametric interaction, specifically the four-wave mixing, plays a fundamental role in influencing the nature of the stationary states observed in a micro-cavity. The results show possible new strategies for enhanced, low-power, all-optical control of sensors, oscillators and chaos-controlled devices. Moreover, the outcomes provide new understanding of the effect of coherent wave mixing in the thermal stability regions of optical micro-cavities, including optical micro-combs.

近年在矽光子學方面的研究日漸增多，主要原因是在高效能電腦，低成本通訊接取網絡及集成光學感應器等各方面有很大的潛在應用。以矽為原材料的各種光學器件已經被廣泛研究，包括電光調制器，光感應器和各式各樣主動及被動器件。但是由於矽是一種間接能隙的物質，即是由電子激發的電子電洞的結合是屬於非輻射躍遷，所以不可以得到光放大和激光器的效果。為了製作集成激光器，已經有很多不同的研究方案，例如在矽波導上摻雜鉺或是混合集成矽和-族半導體。在這篇論文中，我們提出並且論証了一個創新的方案去製作由光纖和矽波導混合而成的激光器，大大簡化了設計和生產過程。 / 在論文中，我們會集中討論選取光波長的器件及整體結構的設計。在首次的結構設計上，我們利用了分佈在矽波導兩側的布拉格反射鏡作為選取光波長的器件和一小段以鉺摻雜的光纖作為放大器。我們將會詳細形容該器件的設計、模擬效果和實驗結果。我們已經透過實驗証明了單波長的光纖－矽波導混合激光器，其側模抑制超過35分貝。 / 另一方面，為了製作多波長的光纖－矽波導混合激光器，我們利用微環諧震器來取代分佈在矽波導兩側的布拉格反射鏡作為選取光波長的器件。我們將會討論微環諧震器的設計以及達到穩定多波長的光纖和矽波導混合激光器的設計要求。 / Motivated by potential applications for optical interconnects in high performance computing, low cost optical access networks in telecommunications and integrated optical sensors, there has been much research in recent years on silicon photonics. Different silicon-based photonic devices have been studied, including optical modulators, detectors and various types of active and passive components. However, since the bandgap of silicon is indirect, the recombination of carriers injected by electrical pumping is dominated by non-radiative transitions and thus it is not possible to get optical gain via current injection into silicon diodes. / To implement integrated laser, different approaches such as erbium doping on silicon waveguide and hybrid integration of III-V semiconductors on silicon have been investigated. In this thesis, we propose and demonstrate a novel approach for making a hybrid fiber-silicon laser to simplify the design and fabrication processes. We propose the use of Erbium-doped fiber (EDF) to provide gain and silicon devices to provide all the other functionalities needed for a modulated laser. / The thesis focuses on the design of wavelength selective element and the structure of hybrid fiber-silicon laser. The first design includes a silicon waveguide side-cladding distributed Bragg reflector (WSC-DBR) as the wavelength selective component on silicon-on-insulator (SOI) wafer and a short length of EDF as the gain medium. The details of design, simulation and experimental results of the WSC-DBR will be described. Single wavelength WSC-DBR hybrid fiber-silicon laser is demonstrated with a side mode suppression ratio (SMSR) of over 35dB. / We also investigate the use of a micro-ring resonator to replace WSC-DBR for selecting multiple wavelengths. Details of the micro-ring resonator are given and we discuss the requirement and design criteria to achieve stable multi-wavelength lasing. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Fung, Ka Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstracts also in Chinese. / ABSTRACTOF THESIS ENTITLED: --- p.ii / ACKNOWLEDGEMENT --- p.v / TABLE OF CONTENT --- p.vii / Chapter 1 --- INTRODUCTION --- p.10 / Chapter 1.1 --- Photonic Integrated Circuits --- p.10 / Chapter 1.2 --- Silicon Photonics --- p.13 / Chapter 1.3 --- Lasers in Silicon --- p.20 / Chapter 1.4 --- Motivation --- p.27 / Chapter 1.5 --- References --- p.29 / Chapter 2 --- ERBIUM DOPED FIEBR AND FIBER LASERS --- p.34 / Chapter 2.1 --- Erbium doped fiber --- p.34 / Chapter 2.2 --- Multi-wavelength lasers --- p.45 / Chapter 2.3 --- References --- p.54 / Chapter 3 --- SINGLE CHANNEL HYBRID FIBER-SILICON LASER --- p.59 / Chapter 3.1 --- Introduction of Distributed Bragg reflector --- p.60 / Chapter 3.2 --- Design of waveguide side-cladding distributed Bragg reflector --- p.63 / Chapter 3.3 --- Simulation results of waveguide side-cladding distributed Bragg reflector --- p.66 / Chapter 3.4 --- Device fabrication --- p.69 / Chapter 3.5 --- Experimental results of waveguide side-cladding distributed Bragg reflector --- p.71 / Chapter 3.6 --- Experimental results of hybrid fiber-silicon laser --- p.77 / Chapter 3.7 --- Introduction of micro-ring resonator --- p.81 / Chapter 3.8 --- Design of race track micro-ring resonator --- p.85 / Chapter 3.9 --- Experimental results of race track micro-ring resonator --- p.88 / Chapter 3.10 --- Experimental results of hybrid fiber-silicon laser with ring resonator --- p.95 / Chapter 3.11 --- Summary --- p.99 / Chapter 3.12 --- References --- p.101 / Chapter 4 --- DUAL WAVELENGTH HYBRID FIBER SILICON LASER --- p.102 / Chapter 4.1 --- Design of micro-ring resonator for dual wavelength --- p.103 / Chapter 4.2 --- Experimental results of micro-ring resonator --- p.104 / Chapter 4.3 --- Experimental results of dual wavelength hybrid fiber-silicon laser --- p.108 / Chapter 4.4 --- Summary --- p.119 / Chapter 4.5 --- References --- p.121 / Chapter 5 --- DUAL WAVELENGTH VERTICAL GRATING COUPLER --- p.123 / Chapter 5.1 --- Introduction of grating coupler --- p.123 / Chapter 5.2 --- Design of dual wavelength vertical grating coupler --- p.125 / Chapter 5.3 --- Simulation of dual wavelength vertical grating coupler --- p.127 / Chapter 5.4 --- Experimental results of dual wavelength vertical grating coupler --- p.135 / Chapter 5.5 --- Summary --- p.138 / Chapter 5.6 --- References --- p.139 / Chapter 6 --- CONCLUSION AND FUTURE WORK --- p.141 / Chapter 6.1 --- Conclusion --- p.141 / Chapter 6.2 --- Future work --- p.144 / Chapter 6.3 --- References --- p.146 / Chapter APPENDIX A: --- PUBLICATION LIST --- p.147 / Chapter APPENDIX B: --- LIST OF TABLES --- p.149 / Chapter APPENDIX C: --- LIST OF FIGURES --- p.150 / Chapter APPENDIX D: --- METHODS OF LINEWIDTH MEASUREMENT --- p.155 / Chapter APPENDIX E: --- EQUIPMENT INFORMATION --- p.164

Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA and polycarbonate.;An anisotropic electromagnetic boundary value model was developed to understand more fully the mechanisms through which photoelastic stress patterns are produced. This model produced intensity contour maps which matched the fringe patterns observed in the laboratory, and allowed the effect of measurement errors on the calculated stress tensor to be quantified. One significant source of error was the retro-reflective backing, which depolarized the light and degraded the resulting photoelastic fringes. A quantitative analysis of the degraded fringes, to be used as a rating scheme for reflective backing materials, showed that the isoclinic lines shift position as a result of the backing roughness and oblique incidence. This is a concern when calculating the stress components through the combination of photoelasticity and thermoelasticity because the data maps are integrated at the pixel level. Small shifts in the photoelastic fringes result in incorrect information being assigned to some pixels and hence lead to uncertainties in the stress tensor components. Progress in the understanding of the depolarization at the reflective backing allows the specification of new materials that will minimize this effect, as well as the development of robust computer algorithms to correct for any remaining depolarization.

Over the last several decades, two methods have emerged as the standard tools for the calculation of electronic band structures. These methods, the Car-Parinello plane wave method and the linear augmented plane wave method (LAPW), each have strengths and weaknesses in different regimes of physical problems. The Car-Parinello algorithm is ideal for calculations with soft pseudopotentials and large numbers of atoms. The LAPW method, on the other hand, easily handles all-electron and hard-core pseudopotential calculations with a small number of atoms. The projector basis method, presented here, is a hybrid mixed basis method which allows the calculation of moderately large ({dollar}\sim{dollar}200) numbers of atoms represented by hard pseudopotentials. This method will then be used to calculate two members of a relatively new mass of materials, called electrides, in which the anion has been replaced with a localized electron.

The conversion from low speed to high speed and vice versa in various forms, including rotary and linear motion, is a requirement for a wide range of applications. For example, wind power generation requires a conversion of low speed rotation of turbine blades to high speed generator rotation, and ocean wave power generation is achievable by conversion of low speed linear motion to either high speed rotation or high speed linear motion. Mechanical gearboxes, hydraulic and pneumatic actuators are commonly used to achieve these conversions. However, these systems suffer from reliability issues, high maintenance requirements, noise, and lack of overload protection. As an alternative, electromagnetic actuators overcome most of the issues related to the mechanical, hydraulic and pneumatic mechanisms. However, magnetic shear stress is constraint by current density and magnetic saturation. Recently, magnetic gearboxes have been proposed, which rely only on magnetic loading. They provide speed and force conversion like their mechanical counterparts, but without thermal constraints (current density limits). Unlike mechanical gears, magnetic gear contact-less operation enables it to operate without lubrication and with low noise, and higher efficiency. Its reliance on magnetic loading also provides overload protection. This dissertation focuses on investigating two new types of magnetic gears; first a magnetically-geared lead screw is proposed, which converts a low speed linear motion to a high speed rotary motion. The proposed actuator is a combination of two previously proposed actuators, the linear magnetic gear and the magnetic lead screw. Unlike these two topologies, the translator part of the proposed magnetically geared lead screw is made entirely of low-cost ferromagnetic steel. Therefore, the translator stroke length can be long without requiring more magnet material. In the second part of this dissertation, an axial flux magnetic gear is proposed that has an integrated outer stator. This axial flux magnetically-geared motor is unique in that the stator shares the high-speed rotor with the magnetic gear, so there is no need for a separate rotor. The high speed and low speed rotors use a flux-focusing typology. The stator is mounted outside the axial flux magnetic gear. This makes the design mechanically less complex. It also enables the stator to be cooled more easily. In the last part of this dissertation, analytical-based models are proposed for a linear permanent magnet coupling and magnetic lead screw. These models help to find the upper bound of the similar devices, which require a scaling analysis. Numerical methods like finite element analysis are accurate and effective enough for modeling various electromechanical and electromagnetic devices. However, these simulations are usually computationally expensive; they require a considerable amount of memory and time, especially when considering 3D finite element simulation. The proposed analytical models offer exact field solution while significantly reducing the computational time. Detailed analysis of two magnetic gears is given under their corresponding chapters. Preliminary experimental results are also provided. The analytical-based model is presented and verified by FEA results. A summary of research contributions and future works is outlined.