By combining experiment and theory, we believe our study shed light on developing a new method for well investigating and controlling the different plasmonic modes and open their way for some great applications in biology, chemistry and photonics. / Finally, this thesis presents an approach to quantitatively evaluate the SP-mediated light emission. Based on this consideration, efforts are taken to find the temperature effect of SP on the light emission in semiconductor. On metal/ZnO system, a more realistic picture for the light emission is depicted by experimentally measuring the temperature-dependent photoluminescence and theoretically calculating the Purcell enhancement factor. The increasing plasmonic density of states with the lower temperature has been regarded as being responsible for the enhanced light emission. / Firstly, studies are performed on finding an in-depth understanding into the optical properties of two-dimensional (2D) metallic nano-cavity structure (grating). Structures are fabricated by interference lithography and thin film techniques. Grating geometries can be easily tuned by using these versatile techniques with high reproducibility and precision. Plasmonic dispersion in the 2D grating has been mapped out by angle-dependent reflectivity measurements. Two particular nanostructures, i.e., nano-bottle array and elliptical hole array, have been chosen to investigate the dependence of plasmonic properties on geometries change. Theories are also put forward to understand the origin and electromagnetic properties of the obtained plasmonic modes. / Surface plasmons (SP), the collective oscillations of the conduction electrons between the metal/dielectric interface, strongly influence the optical properties of metallic nanostructures and are of great interest for future photonic devices. Here, this thesis mainly focuses on the experimental and theoretical investigations on the optical properties of the metallic periodic nanostructures. / With an understanding into the different plasmonic properties of the metallic nanostructures, researches are then undertaken to explore how this associated electromagnetic field interacts with the molecules adsorbed onto a sample surface. The distinct and strong correlation between the plasmonic modes and surface enhanced Raman scattering (SERS) is verified on the one-dimensional silver grating. In particular, the detailed analysis of the enhancement factor from surface plasmons excitation and de-excitation process in SERS has been performed. On the other hand, the technique used to fabricate the controllable "hot spot" for enhancing Raman scattering has been introduced on the 2D metallic grating. Complemented by the theoretical simulation, the conditions for optimizing SERS enhancement effect are proposed. / Li, Jia = 週期性金屬鈉米結構光學特性的實驗和理論研究 / 李佳. / Adviser: Ong Hock Chun. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0388. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 135-144). / 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 Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / Li, Jia = Zhou qi xing jin shu na mi jie gou guang xue te xing de shi yan he li lun yan jiu / Li Jia.

I believe that my research work on the plasmonic spectroscopy of metallic nanostructures has provided an in-depth fundamental understanding of the localized surface plasmon resonance and will have a number of implications for the applications of metallic nanostructures in optics, optoelectronics, and biotechnology. / I will first describe my studies on the plasmonic properties of metallic nanostructures. Specific approaches of modifying the sizes and shapes of Au nanorods have been developed for tailoring their plasmonic properties, including surface plasmon wavelength, absorption, scattering, and extinction cross sections. Single-particle dark-field imaging and spectroscopy have proved that the scattering intensity of overgrown nanorods is larger than that of shortened nanorods from the same starting nanorods. Finite-difference time-domain (FDTD) calculations further show that the scattering-to-extinction ratio increases linearly as a function of the diameter of Au nanorods with a fixed aspect ratio. To obtain a deep understanding on the shape dependence of the localized surface plasmon resonance, I have emplyed FDTD on both Au nanorods and Au nanobipyramids. The results show that, when excited at their LSP wavelengths, Au nanobipyramids exhibit a maximal electric field intensity enhancement that is 3--6 times that of Au nanorods. Au nanorods have been further assembled into chains (end-to-end) and stacks (side-by-side). FDTD calculations have been performed on both Au nanorod chains and stacks with varying gap distances to obtain the dependence of the plasmon shift on the gap distance, which is then used as a plasmonic ruler to estimate the gap distance between assembled nanorods. Moreover, dye--Au nanorod hybrid nanostructures have also been successfully fabricated for the study of the coupling between the transition dipole resonance and the plasmonic resonance. The coupling-induced plasmon shift is found to be strongly dependent on molecular properties, the dye concentration in solutions, and the spacer thickness between dye molecules and the surface of Au nanorods. The coupling can be switched off by means of laser-induced photodecomposition of dye molecules. / Next, I will present my studies on the applications of metallic nanostructures. A SERS substrate has been constructed by assembling silver nanoparticles along silica nanofibers. The enhancement factors are found to be 2 x 10 5 for 4-mercaptobenzoic acid and 4-mercaptophenol, and 7 x 10 7 for rhodamine B isothiocyanate. A novel plasmonic optical fiber device has further been fabricated to detect small changes in the local dielectric environment. For individual Au nanorods, the index sensitivity and figure of merit (FOM) are found to be linearly dependent on the longitudinal plasmon resonance wavelength and reach 200 nm/RIU and 3.8, respectively. For nanorod ensembles, the index sensitivity and FOM of the longitudinal plasmon resonance are found to be 138 nm/RIU and 1.2, respectively. / The study of the plasmonic spectroscopy of metallic nanostructures is of great interest in nanoscale optics and photonics. Metallic nanostructures exhibit rich optical and electrical properties due to their localized surface plasmons (LSPs, collective charge density oscillations that are confined to metallic nanostructures). They can be widely used in a variety of application areas, such as surface-enhanced Raman scattering (SERS), plasmonic sensing, and metal enhanced fluorescence (MEF). In this thesis, a systematic study on the plasmonic spectroscopy of metallic nanostructures has been presented, both theoretically and experimentally. / Ni, Wei hai = 金屬納米結構的等離子體光譜 / 倪衛海. / Adviser: Jianfang Wang. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3580. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 135-154). / 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, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307. / Ni, Wei hai = Jin shu na mi jie gou de deng li zi ti guang pu / Ni Weihai.

A metal-oxide-silicon (MOS) tunneling diode is utilized to embed beta-FeSi 2 precipitates and give strong 1.5 tam electroluminescence at 80 K. And this simple MOS structure with beta-FeSi2 was fabricated by Fe ion implantation and rapid thermal oxidation (RTO) at 900°C, which is fully compatible with ultra-large scale integration (ULSI) processes. / beta-FeSi2 precipitates are also incorporated into a silicon-on-insulator (SOI) rib waveguide and a p+-i-n+ photodetector is monolithically integrated with this SOI rib waveguide. The photoresponse to 1550 nm laser of beta-FeSi2 precipitates was observed and compared to intrinsic silicon. / Beta-phase iron disilicide (beta-FeSi2) is a semiconductor that can act as a light emitting material at the wavelength of 1.55 mum and can also be grown epitaxially on Si substrates. In this thesis, Fe ion implantation into silicon using a metal vapor vacuum arc (MEVVA) ion source was performed to synthesize nano-scale beta-FeSi2 precipitates in silicon matrix. The implantation was performed at ∼-120°C and the effects of silicon substrate and conditions for the following thermal annealing on luminescence properties were studied. The samples were characterized by employing various analytical techniques including Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), atomic force microscope (AFM), photoluminescence (PL), and electroluminescence (EL). / It is found that the PL intensity is optimized in p-100 silicon substrates (with the resistivity of 15-25 O·cm) using Fe ion implantation at a voltage of 80 kV and dosage of 5x1015 cm -2. Formation of beta-FeSi2 can be completed after rapid thermal annealing (RTA) and strong photoluminescence is present. We also found that RTA could maintain the strain in beta-FeSi2 precipitates and there exists an epitaxial relationship between beta-FeSi2 and silicon. Additional furnace annealing at 850°C can relax the strain in beta-FeSi2 precipitates. / The development of both modern microelectronics and lightwave technologies has enabled the establishment of the Internet which has introduced a profound change in our everyday lives. Because of Moore's law, computing today is limited less by the computation ability of microprocessors than by the rate at which the processor can communicate with the outside world. Lightwave technology has had many successes in the long-haul communication field over the past decade. The advantages of lightwave technology over conventional electronics are becoming apparent for shorter and shorter reach applications and lightwave communications may eventually replace copper-based interconnects in microelectronics. To make possible optical interconnects, optical components, especially light emitters may be needed to be integrated on conventional silicon microchips. However, to date, no efficient on-chip silicon-based light emitter is fabricated in silicon photonics. / Sun, Caiming. / Adviser: Hon K. Tsang. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3703. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / 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, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Shi Lei = 溶凝膠分佈反饋波導激光器之光學性質的研究 / 石蕾. / "September 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 150-171) / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Shi Lei = Rong ning jiao fen bu fan kui bo dao ji guang qi zhi guang xue xing zhi de yan jiu / Shi Lei.

In our research Hyper-Rayleigh scattering (HRS) is employed as an effective, simple investigation technique to study solutions of small molecules, pure liquids, nano-adsorbing systems and metal colloids. A set of apparatus has been built with good spectral resolution and high sensitivity to successfully measure characteristics of intensity and polarization properties of HRS. It was found that the consistency was different for pure liquid and solutions of small molecules when comparing experimental measurements of depolarized ratios and polarization patterns with theoretical expectations. This is due to the presence of both incoherent and coherent contributions to HRS in pure liquids, of which the origin of the coherent contribution is different for different pure liquids. In our results, pure liquid nitrobenzene was found to have strong coherent contribution to HRS caused by intermolecular interactions. Three different chemical compounds were used to mix with nitrobenzene to break the strong orientational correlations between molecules. Comparison between the results show different behaviors in the effectiveness in eliminating the coherent HRS signals, and the effectiveness was correlated to the molecular structures. Theory of second harmonic scattering from surface has been expanded as leading order contributions containing nonlocal electric dipole mode and local quadrupole mode, which can be exhibited in our experimental study of polarization patterns. Polarization patterns from polystyrene particles of different sizes adsorbed with different species of dyes were measured to investigate and compare with theoretical expectations. For small-size adsorbing system, measurements of polarization patterns were basically consistent with theory. However, for adsorbing system of polystyrene particles with a size of 900 nm, the polarization patterns showed discrepancies when comparing with theory, which indicated that higher order multipoles are needed in the theory. Silver and gold colloids were employed as the subject of investigation for measuring the polarization patterns of HRS. The results were found to be consistent when comparing with their extinction spectra and TEM images. We have managed to measure polarization patterns of HRS originated from surface of non-spherical colloids and the results showed that the origin of HRS can be qualitatively understood, although a more elaborated theory is needed to describe the data. / by Chen, Ji = 由有機液體以及金屬膠體產生的非線性光散射的研究 / 陳佶. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 117-118). / 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, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307. / by Chen, Ji = You you ji ye ti yi ji jin shu jiao ti chan sheng de fei xian xing guang san she de yan jiu / Chen Ji.

The optical response of metallic structures is dominated by the dynamics of their free electron plasma. Plasmonics, the area of optics specializing in the electromagnetic behavior of heterogeneous structures with metallic inclusions, is undergoing rapid development, fueled in part by recent progress in experimental fabrication techniques and novel theoretical approaches. In this thesis I outline the behavior of four plasmonic material systems, and discuss the underlying physics that governs their optical response. First, the anomalous optical properties of solution-derived percolation films are explained using scaling theory. Second, a novel technique is developed to characterize the optics of amorphous nanolaminates, leading to the creation of a meta-material with anisotropic (hyperbolic) dispersion. The properties of such materials can be tuned by adjusting their composition. Third, the electrodynamics of vertically aligned multi-walled carbon nanotubes is derived through the development of a spectroscopic terahertz transmission ellipsometry algorithm. Lastly, a new diffraction based imaging structure based on metallic gratings is presented to have resolution capabilities which far outperform the diffraction limit. / Graduation date: 2013

Atomically thin group-VI transition metal dichalcogenides (TMDC) has been emerging as a family of intrinsic 2-dimensional (2D) crystals with a sizeable bandgap in the visible and near infrared range, satisfying numerous requirements for ultimate electronics and optoelectronics. This intrinsic 2D crystal also provides a perfect platform for physics study in 2D semiconductors. The characteristic inversion symmetry breaking presented in monolayer TMDCs leads to non-zero but contrasting Berry curvatures and orbital magnetic moments at K/K’ valleys located at the corners of the first Brillouin zone. These features provide an opportunity to manipulate electrons’ additional internal degrees of freedom, namely the valley degree of freedom, making monolayer TMDC a promising candidate for the conceptual valleytronics. Besides, the strong spin-orbit interactions and the subsequent spin-valley coupling demonstrated in 2D TMDCs open potential new routes towards quantum manipulation. In this thesis, I give a brief review on the background and our progress of the physics study in 2D TMDCs (MoS2, WS2) via optical spectroscopy. Particularly, our experimental approach on the excitonic effect, valley dependent circular dichroism, and the spin-valley coupling in monolayer and bilayer TMDCs are elaborated in individual chapters. / published_or_final_version / Physics / Doctoral / Doctor of Philosophy

The research results contained in this dissertation relate to the novel field of engineered tissue optics. Biological tissue such as skin is highly opaque due to multiple light scattering. However, it has been shown that certain hyper-osmotic chemicals can temporarily render turbid tissues such as skin optically transparent by reducing light scattering. The mechanisms involved in this process are believed to be a combination of dehydration and index matching. In order to capitalize on the non-invasive nature of light-tissue interactions for diagnostic and therapeutic purposes, hyper-osmotic optical clearing agents need to be delivered transepidermally. The first part of this dissertation is devoted to investigation of different methods to temporarily reduce the natural skin barrier posed by the stratum corneum in order to allow topically applied optical clearing agents to diffuse into epidermis and dermis. Methods such as needle-free injection gun, micro-needles, Er:YAG surface ablation, use of a 980 nm diode laser and mild surface abrasion using sandpaper were investigated. The second part of this dissertation investigated the effects of optical tissue clearing on tissue structure and influence on blood flow. Various imaging modalities such as optical coherence tomography (OCT), microscopy, confocal microscopy as well as transmission electron microscopy were employed to deduce how tissue structural changes can explain the temporary reduction of light scattering. / text

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