This thesis describes a detailed study of advanced optical fibre sensors based on fibre Bragg grating (FBG), tilted fibre Bragg grating (TFBG) and long-period grating (LPG) and their applications in optical communications and sensing. The major contributions presented in this thesis are summarised below. The most important contribution from the research work presented in this thesis is the implementation of in-fibre grating based refractive index (RI) sensors, which could be the good candidates for optical biochemical sensing. Several fibre grating based RI sensors have been proposed and demonstrated by exploring novel grating structures and different fibre types, and employing efficient hydrofluoric acid etching technique to enhance the RI sensitivity. All the RI devices discussed in this thesis have been used to measure the concentration of sugar solution to simulate the chemical sensing. Efforts have also been made to overcome the RI-temperature cross-sensitivity for practical application. The demonstrated in-fibre grating based RI sensors could be further implemented as potential optical biosensors by applying bioactive coatings to realise high bio-sensitivity and bio-selectivity. Another major contribution of this thesis is the application of TFBGs. A prototype interrogation system by the use of TFBG with CCD-array was implemented to perform wavelength division multiplexing (WDM) interrogation around 800nm wavelength region with the advantages of compact size, fast detection speed and low-cost. As a high light, a novel in-fibre twist sensors utilising strong polarisation dependant coupling behaviour of an 81°-TFBG was presented to demonstrate the high torsion sensitivity and capability of direction recognition.

Lai, Wai Chiu King. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 87-89). / Abstracts in English and Chinese. / LIST OF TABLES --- p.vi / LIST OF FIGURES --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Organization of the thesis --- p.3 / Chapter 2. --- Literature Survey --- p.5 / Chapter 2.1 --- Micro Hinges --- p.5 / Chapter 2.2 --- Assembly --- p.5 / Chapter 2.2.1 --- Manual Lift Up Process --- p.5 / Chapter 2.2.2 --- Assembly by On-substrate Actuators --- p.6 / Chapter 2.2.3 --- Assembly by Surface Tension Force --- p.8 / Chapter 2.2.4 --- Assembly by Thermal Shrinkage --- p.8 / Chapter 2.2.5 --- Assembly by Ultrasonic Triboelectricity --- p.9 / Chapter 2.3 --- Summary of Literature Survey --- p.9 / Chapter 3. --- Design & Analysis --- p.11 / Chapter 3.1 --- Micro-Assembly by Centrifugal Force --- p.11 / Chapter 3.2 --- Micro Mass Platform --- p.12 / Chapter 3.2.1 --- Micro Mirror --- p.12 / Chapter 3.2.2 --- Rotation Sensor --- p.15 / Chapter 3.3 --- Fabrication of Micro Structures --- p.16 / Chapter 3.4 --- Force Analysis --- p.18 / Chapter 3.4.1 --- Centrifugal Force --- p.18 / Chapter 3.4.2 --- Van der Waals Forces --- p.20 / Chapter 3.4.3 --- Capillary Force - (1st model) --- p.22 / Chapter 3.4.4 --- Capillary Force - (2nd model) --- p.23 / Chapter 3.4.5 --- Casimir Force --- p.26 / Chapter 3.4.6 --- Spring force of the beam --- p.27 / Chapter 3.4.7 --- Comparison of Forces --- p.28 / Chapter 3.4.8 --- Stress on Polysilicon --- p.30 / Chapter 4. --- Surface Force Measurement --- p.32 / Chapter 4.1 --- Experimental Setup --- p.33 / Chapter 4.2 --- Experimental Result --- p.34 / Chapter 4.2.1 --- Control Experiment of Rotation Sensor --- p.34 / Chapter 4.2.2 --- Freed-state and Snap-down-state --- p.35 / Chapter 4.2.3 --- Summary of the Experimental Data --- p.36 / Chapter 4.3 --- Comparison between Modelled Results and Experimental Data --- p.42 / Chapter 5. --- Assembly Experiment --- p.45 / Chapter 5.1 --- Experimental Setup --- p.45 / Chapter 5.2 --- Experimental Results --- p.46 / Chapter 5.3 --- Comparison among different chips --- p.52 / Chapter 6. --- Assembly Experiment (Double Chips) --- p.57 / Chapter 6.1 --- Experimental Setup --- p.57 / Chapter 6.2 --- Experimental Results --- p.58 / Chapter 6.2.1 --- Surface Profile measurement --- p.58 / Chapter 6.2.2 --- Summary of the surface profile measurement --- p.68 / Chapter 6.2.3 --- Assembly Results --- p.69 / Chapter 7. --- Assembly Experiment (Monitoring System in MUMPs46) --- p.72 / Chapter 7.1 --- Experimental Setup --- p.72 / Chapter 7.2 --- Experimental Results --- p.74 / Chapter 8. --- Other tested micro structures --- p.80 / Chapter 9. --- Conclusion --- p.82 / Chapter 10. --- Future Work --- p.83 / Chapter A. --- Appendix --- p.84 / Bibliography --- p.87

In the last decade, the emerging classes of two-dimensional (2D) materials have been studied as potential candidates for various sensing technologies, including magnetic and optoelectronic detectors. Within the quickly growing portfolio of 2D materials, graphene and semiconducting transition metal dichalcogenides (TMDs) have emerged as attractive candidates for various sensor applications because of their unique properties such as extreme thickness, excellent electrical and optical properties. In this thesis, I have exploited the unique properties of graphene and TMDs materials to develop 2D detectors based on field effect transistors for sensing magnetic field and light. In the first part of this thesis I have shown how the sensitivity of the properties of 2D materials to their surrounding environment can be turned into a feature useful to create new types of magnetic field sensors. The first experimental demonstration of this concept involved the use of graphene deposited on hexagonal Boron Nitride (h-BN), where the inevitable contaminations occurring at the interface of the two materials was used to generate a large magnetoresistance (MR) for a magnetic field sensor. Specifically, I have demonstrated that the contaminations generate an inhomogeneity in the carrier mobility throughout the channel, which is a required ingredient for magnetic field sensing based on linear magnetoresistance (LMR). Another approach I used to make a LMR sensor was by exploiting the large dependence of the mobility in graphene on the Fermi level position. This concept was used to generate two parallel electron gases with different mobility by tuning the Fermi level with an electrical field employing a field effect transistor. The second part of the thesis is focussed on strategies to reduce the impact of the surrounding environment on the properties of 2D materials in order to improve their performance. In particular, I used a 2D heterostructure encapsulated in an ionic polymer to makeii a highly responsive graphene-TMD photodetector. In this device, the ionic polymer covering the heterostructure was employed to screen the long-lived charge traps that limit the speed of such detectors, resulting in a drastic improvement of the detector responsivity properties. Finally, some of the 2D materials properties are very sensitive to the configuration of the electronics measurement setup. For example, effects behind spintronic and valleytronic concepts require non-local electrical transport measurement. We built a novel circuit that enables the detection of such effects without concern about the spurious contributions.

No description available.

Chow Kin Kee. / May, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / 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.

In this work, the author aims to trace some of the transformative effects of televisual technologies in contemporary post-industrial culture, and to critically assess their impact on the way knowledge is produced, and experience a sense of embodiment and social agency. The relation between humans and tools is questioned, and the hybridity of words such as technoculture and biotechnology is investigated, arguing that the separation of human and technology,and body and tool, at the level of both existence and knowledge is a synthetic distinction. Specifically, the author concentrates on some of the medium specific effects of postclassical visualising technologies, from high-end ensembles such as virtual reality and medical imaging apparatuses, to the mundane apparatus of television and the remote control device. Such ways of seeing, it is argued, collaborate in producing an emergent tele-body, or a telesomatic mode of perception and knowing which exceeds standard epistemologies of vision in both science and the everyday. This work thus aims to develop a theoretical and conceptual framework for understanding the variable effects of postclassical technovision and televisuality upon our modes of embodiment. / Doctor of Philosophy (PhD)

Thesis (Ph.D.)--McMaster University, 2006. / Supervisor: P.E. Jessop Includes bibliographical references ( leaves 166-179).

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Room temperature vertical cavity lasing at the wavelength of 433nm has been successfully realized in InxGa₁₋xN/InyGa₁₋yN multiple quantum well without Bragg mirrors under photo-excitation. At high excitation intensity, one of the modes of the Fabry-Perot cavity formed by the GaN/sapphire and the GaN/air interfaces, shows a strong superlinear increase in intensity with excitation intensity rise. The vertical cavity surface emitting laser (VCSELs) structure is grown by metal-organic chemical vapor phase deposition and the threshold is as low as 200kW/cm². The lasing in the sample probably results from the ultrahigh material gain due to the spontaneous formation of dense array of nanoscale InGaN quantum dots (QDs) having an exceptional high area density. / Singapore-MIT Alliance (SMA)

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 26, 2007) Vita. Includes bibliographical references.