Yu, Tsz Tat. / "December 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 143-147). / Abstracts in English and Chinese. / Abstract --- p.2 / 摘要 --- p.4 / Acknowledgements --- p.5 / List of Figures --- p.6 / List of Tables --- p.12 / List of Abbreviations --- p.13 / Table of Contents --- p.14 / Chapter Chapter 1 --- Introduction --- p.17 / Chapter Chapter 2 --- Literature Review / Chapter 2.1 --- Surface Plasmon Wave --- p.19 / Chapter 2.2 --- Excitation of Surface Plasmon --- p.23 / Chapter 2.3 --- Surface Plasmon Coupling --- p.24 / Chapter 2.4 --- Surface Plasmon Resonance Detection Techniques --- p.33 / Chapter 2.5 --- Applications of SPR biosensors --- p.39 / Chapter Chapter 3 --- Theory of irradiance modulator / Chapter 3.1 --- Polarization --- p.44 / Chapter 3.2 --- Optical polarizer --- p.45 / Chapter 3.3 --- Liquid Crystal Modulator --- p.49 / Chapter 3.4 --- Irradiance Modulator --- p.52 / Chapter Chapter 4 --- LCM characterization / Chapter 4.1 --- Single LCM Transmittance driven by pure square wave --- p.66 / Chapter 4.2 --- Single LCM Reflectance driven by 50:50 STAM wave --- p.70 / Chapter 4.3 --- Multiple LCMs Reflectance driven by 90:10 STAM wave --- p.73 / Chapter Chapter 5 --- Background of phase measurement / Chapter 5.1 --- From holography to shearography --- p.77 / Chapter 5.2 --- From static Mach-Zehnder interferometer to differential-phase Mach-ZehnderZ interferometer --- p.81 / Chapter 5.3 --- From differential-phase imaging to pixel-referencing imaging --- p.86 / Chapter Chapter 6 --- Pixel-referencing data processing / Chapter 6.1 --- Background --- p.89 / Chapter 6.2 --- Procedures --- p.94 / Chapter 6.3 --- Experimental results --- p.98 / Chapter 6.4 --- Sensor resolution --- p.116 / Chapter 6.5 --- Performance comparison between single-beam LCM and Mach Zehnder configuration --- p.119 / Chapter Chapter 7 --- Discussions / Chapter 7.1 --- Experiment precautions --- p.136 / Chapter 7.2 --- Linear curve fitting --- p.137 / Chapter 7.3 --- Hardware limitation: Low frame rate --- p.138 / Chapter 7.4 --- Matching oil and glass slide --- p.139 / Chapter Chapter 8. --- Conclusions --- p.141 / References --- p.143 / Appendix / Chapter A1 --- "Concentration, Refractive Index and Dielectric constant of Sodium Chloride Solution (20°C)" --- p.148 / Chapter A2 --- Liquid Crystal Modulator Specification --- p.149 / Chapter A3 --- "Digital-to-analogue Converter Device (NI, PCI6036E) Datasheet" --- p.150 / Chapter A4 --- "CCD Camera (Lumenera, Infinity) Datasheet" --- p.151 / Chapter A5 --- Flow chart of SPR phase extraction --- p.152 / Chapter A6 --- Codes of SPR phase extraction in modules --- p.153

The birefringence of one-dimension PMMA surface gratings on a gold film substrate is investigated. The grating served as a coupler to facilitate the incoming light coupled to surface plasmon wave (SPW) which possesses high propagation wave vector. Since surface plasmon waves(SPWs) have a special dispersion relation, the birefringence £Gneff (£Gneff =nx-ny, where grating k-vector is along x axis) of this structure is relatively large and can be changed from positive to negative by changing the operation wavelength. The obtained the four Stokes parameters at 515nm and 633nm are marked on the Poincare sphere. £Gneff is 2£k/7 and -£k/8 at 515nm and 633nm respectively. Further, by changing the form factor of PMMA gratings, we found that the maximum £Gneff occurred when PMMA stripe width : air gap=1:1.

The attenuated total reflection (ATR) due to excitation of surface plasmon is usually applied to study the dielectric coefficient. In this study the surface plasmon has been excited on the interface between the liquid crystal and silver in Krestchmann configuration. We can obtain the effective reflection index and the tilt-angle of liquid crystal anchored on the interface with the excitation condition of surface plasmon. We also discuss the variation of the tilt-angle of liquid crystal with the various applied bias.

Collective oscillation of conduction electrons in metallic nanoparticles known as localized surface plasmon resonance has been studied for nano-optics applications. The excitation of localized surface plasmons on nano-structured metal material leads to strong light scattering and absorption. Since the localized surface plasmon resonance is strongly dependent on the shape, size, size distribution, and dielectric property of surrounding environment of nano-structured metal, the dependence can be applied in wide applications. However, the direct and non-destructed observation of nano-structured metal is required to the development of nano-technology, we proposed a real time optical observation due to the optical respons of metal nano-particles system. Furthermore, we proposed a fast and simple method to fabricate a high order metal nano-particles array and used liquid crystal material to directly modulate the surface plasmon effect on the metal nanoparticles. The purpose of this work is to study the surface plasmon effect excited on metal nanoparticles. These works are described as follows: A. The topic of the first work is ¡§Real time absorbance spectra due to optical dynamics of silver nano-particles film¡¨, we report the real time absorbance spectra due to optical dynamics of silver nano-particles film under a heating treatment from 28 to 300 ¢J. A 7nm-thicked sliver film was thermally deposited on an indium tin oxide glass substrate. In the process of heating, the real time absorbance spectra of silver nano-particles film were measured by an optical spectrometer. It was noted that the absorbance spectra of the film varied with the heat-treating temperature and time. The peak position in the spectra curve shifted to shorter wavelength below the temperature of 250 ¢J, then shifted to red band due to higher temperature treatment. With the comparison of scanning electron micrograph analysis, the real time absorbance spectra exhibited a particular optical property confirmed by the dynamic dark-field optical microscopy system. The real-time absorbance spectra and dark-field micrographs analyses lead to a direct and non-destructed observation of growing evolution of metal nano-particles. B. The topic of the second work is ¡§Laser pulse induced gold nanoparticles grating¡¨. We report the results of our experimental investigation of laser induced gold nano-particle gratings and their optical diffraction properties. A single shot of a pair of Nd-YAG laser pulses of the same polarization is directed toward a thin gold film of thickness 6 nm on a substrate of polymethyl methacrylate (PMMA). As a result of the laser illumination, the thin gold film is fragmented into an array of nano-particles. Using scanning electron and dark-field optical micrographs, we discovered that the morphology of the gold nanoparticles grating is dependent on the fluence of laser pulse. The spectrum of first order diffraction shows a spectral dependence, possibly due to the presence of the nano-particles of various sizes. The ablation of thin films of nano-thickness via the use of laser pulses may provide a simple and efficient method for the fabrication of nano-scale structures, including 2D arrays of nano-particles. C. The topic of the second work is ¡§Surface plamons induced extra diffraction band of cholesteric liquid crystal grating¡¨. We investigated the diffraction behavior of cholesteric liquid crystal (CLC) grating with the surface plasmon effect was investigated. One indium-tin-oxide plate of the CLC grating cell was covered with silver nanoparticles. With the application of a proper voltage, a well formed phase grating was constructed in the CLC cell. The CLC grating was probed by a beam of the polarized-monochromatic light, and the wavelength range was from 450 to 700 nm. It was shown that an extra first-order diffraction band was observed around 505 nm. The physical reason of the extra diffraction band could be the surface plasma effect emerged from silver nanoparticles. The extra diffraction band due to the surface plasmon effect can offer potential applications in nano-optics, such as the optical switch function.

Surface plasmons are of interest for various applications, including optical interconnects and devices, light sources, nanolithography, biosensors, solar cells, and negative-refraction prisms or superlenses. Some of the most important applications are SP-based optical interconnects and devices, which offer the potential of realizing integrated optical nanocircuitry due to the subwavelength confinement and the slow-wave nature of SPs. The fundamental building element of these applications is the plasmonic waveguide. Among the family of various plasmonic waveguides, the metal-insulator-metal waveguide has superior lateral confinement because of the relatively shallow field penetration into the metal claddings (about a skin depth -- usually tens of nanometers). Such subwavelength confinement cannot be achieved by conventional dielectric optical waveguides. However, the loss in the MIM waveguide is substantial due to the strong absorption of metal in the visible or near-infrared spectrum. Therefore, the design, simulation, and measurement of the loss in the MIM waveguide are critically important in the development of SP-based nanocircuitry. Surface plasmons (SPs) are of interest for various applications, including optical interconnects and devices, light sources, nanolithography, biosensors, solar cells, and negative-refraction prisms or superlenses. Some of the most important applications are SP-based optical interconnects and devices, which offer the potential of realizing integrated optical nanocircuitry due to the subwavelength confinement and the slow-wave nature of SPs. The fundamental building element of these applications is the plasmonic waveguide. Among the family of various plasmonic waveguides, the metal-insulator-metal (MIM) waveguide has superior lateral confinement because of the relatively shallow field penetration into the metal claddings (about a skin depth -- usually tens of nanometers). Such subwavelength confinement cannot be achieved by conventional dielectric optical waveguides. However, the loss in the MIM waveguide is substantial due to the strong absorption of metal in the visible or near-infrared spectrum. Therefore, the design, simulation, and measurement of the loss in the MIM waveguide are critically important in the development of SP-based nanocircuitry. Owing to the subwavelength sizes of MIM waveguides, the excitation of an MIM plasmonic mode typically requires end-fire coupling with tapered fibers or waveguides. Further, the conventional loss measurements require the usage of a near-field scanning optical microscopy (NSOM) or multiple waveguide samples with various length scales; however, the two aforementioned techniques are both complicated and have issues of sensitivity to uncontrollable environmental factors or variations in coupling strength, respectively. These experimental challenges have been a primary reason for the slow experimental development of the MIM waveguide and device. The research in this thesis focuses on the development of the transverse transmission/reflection (TTR) method, which is a more reliable, accurate, and straightforward method of characterizing the plasmonic modes in the MIM waveguide. The theory of the TTR method, which incorporates an attenuated total reflection (ATR) configuration, is developed based on the transmission matrix formulation. A methodology for obtaining the propagation constant and attenuation coefficient of a plasmonic mode in an MIM waveguide is illustrated. Using the Metricon Prism Coupler, the TTR method is experimentally applied to planar, single-mode MIM (Au-SiO$_2$-Au) waveguides with various core thicknesses at $lambda=1550$ nm. The experimental results are in very good agreement with the theoretical results. It is also shown experimentally that the TTR method is robust against difficult-to-quantify parameters such as the metal cladding thickness and the air gap thickness between the prism and the waveguide. As a result, the TTR method can be readily applied by using other similar ATR or prism-coupler configurations, without concern for the sensitivity issues caused by the subtle differences between various configurations. Moreover, the TTR method is also experimentally applied to planar, multimode MIM waveguides. Multimode MIM waveguides, which have larger core sizes, may be of interest for applications in low-loss interconnects or tapered end-couplers. Thanks to the superior angular selectivity of the ATR configuration, the TTR method is capable of detecting the propagation constant and attenuation coefficient of each mode. To the best of the author's knowledge, this is the first time the propagation constant of each mode in a multimode MIM waveguide has been individually measured. Also, to the best of the author's knowledge, this is the first time the attenuation coefficient of each mode in a multimode MIM waveguide has been individually measured. The TTR method is proved to be a reliable, accurate, and straightforward approach to characterize plasmonic modes in MIM waveguides. Future research will target the extension of the TTR method to 2D MIM waveguides, asymmetric MIM waveguides, and inclusion of scattering loss. Taking full advantage of the TTR method, the development of plasmonic devices can be potentially accelerated. The theory of the TTR method, which incorporates an attenuated total reflection (ATR) configuration, is developed based on the transmission matrix formulation. A methodology for obtaining the propagation constant and attenuation coefficient of a plasmonic mode in an MIM waveguide is illustrated. Using the Metricon Prism Coupler, the TTR method is experimentally applied to planar, single-mode MIM (Au-SiO$_2$-Au) waveguides with various core thicknesses at $lambda=1550$ nm. The experimental results are in very good agreement with the theoretical results. It is also shown experimentally that the TTR method is robust against difficult-to-quantify parameters such as the metal cladding thickness and the air gap thickness between the prism and the waveguide. As a result, the TTR method can be readily applied by using other similar ATR or prism-coupler configurations, without concern for the sensitivity issues caused by the subtle differences between various configurations. Moreover, the TTR method is also experimentally applied to planar, multimode MIM waveguides. Multimode MIM waveguides, which have larger core sizes, may be of interest for applications in low-loss interconnects or tapered end-couplers. Thanks to the superior angular selectivity of the ATR configuration, the TTR method is capable of detecting the propagation constant and attenuation coefficient of each mode. To the best of the author's knowledge, this is the first time the propagation constant of each mode in a multimode MIM waveguide has been individually measured. Also, to the best of the author's knowledge, this is the first time the attenuation coefficient of each mode in a multimode MIM waveguide has been individually measured. The TTR method is proved to be a reliable, accurate, and straightforward approach to characterize plasmonic modes in MIM waveguides. Future research will target the extension of the TTR method to 2D MIM waveguides, asymmetric MIM waveguides, and inclusion of scattering loss. Taking full advantage of the TTR method, the development of plasmonic devices can be potentially accelerated.

Cellulose is the most plentiful biopolymer on the planet, and as such, is a large potential energy source. Converting cellulose into ethanol first requires the disruption of the crystallinity of cellulose fibers and subsequent hydrolysis into glucose. The glucose can then be fermented, producing ethanol. The conversion of cellulose fibers to glucose is an energy intensive and costly step, which is a barrier to industrial production of cellulosic ethanol. The use of enzymes to facilitate this conversion is a promising approach. In the present study, the action of individual enzymes and combinations of enzymes from the Hypocrea jecorina secretome on bacterial cellulose fibers has been studied, to better understand their individual and synergistic action. I have used a custom Surface Plasmon Resonance imaging (SPRi) device to measure changes in the thickness of cellulose fiber coverage of a thioglucose-functionalized gold substrate upon exposure to enzymes. The cellulose fibers were deposited using a Langmuir-Blodgett technique, resulting in non-uniform cellulose coverage of the substrate. By defining local Regions of Interest (ROIs) of the cellulose-covered gold film, and by measuring the SPR curves at elevated temperature for the ROIs as a function of time, we are able to determine the rate and extent of degradation of the cellulose fibers within individual ROIs. We have fit the change in SPR angle over time after exposure to enzyme to an exponential decay function that allows us to determine the average time constant of action of these enzymes on the deposited cellulose fibers. We have used the above procedure to measure the average time constants of action and the average degradation fraction (the change in average thickness divided by the initial average thickness) of cellulose fibers exposed to CBH-1, CBH-2, and EG-1, as well as combinations of these enzymes. We have measured an increase in the average degradation fraction and a decrease in the average time constants of action for cellulose fibers exposed to 23 μg/mL CBH-2 compared to fibers exposed to the same concentration of CBH-1. Additionally, for concurrent exposure of CBH-1 and EG-1 (with individual concentrations of 23 μg/mL), as well as concurrent introduction of CBH-1, CBH-2 and EG-1, we observed increases in the average degradation fraction and decreases in average time constants relative to the values measured for the individual enzymes. These measurements allow us to determine the relative activity of these enzymes and they demonstrate cooperativity and complementarity of action of the different enzymes.

A tunable polarization modulator based on the periodic metal strips embedded in a polymer waveguide is presented. The periodic metallic structure is analyzed by Finite Element simulation (COMSOL). The calculation results show that the giant birefringence is formed by the selective cut-off of TE polarization over TM polarization, which makes it possible to design an efficient polarization modulator with a short conversion length. The metallic strips are made by using four-layer lift-off fabrication technology. The transmission and group indices of TE and TM modes are measured. However, it is observed that TE and TM modes cut off at same time, which does not agree with our predictions. The reason for failure is that the change in refractive indices is different from what we expected, which makes the device perform in opposite way. Finally, further suggestions are provided to modify the design so that the device can achieve its expected function.

A tunable polarization modulator based on the periodic metal strips embedded in a polymer waveguide is presented. The periodic metallic structure is analyzed by Finite Element simulation (COMSOL). The calculation results show that the giant birefringence is formed by the selective cut-off of TE polarization over TM polarization, which makes it possible to design an efficient polarization modulator with a short conversion length. The metallic strips are made by using four-layer lift-off fabrication technology. The transmission and group indices of TE and TM modes are measured. However, it is observed that TE and TM modes cut off at same time, which does not agree with our predictions. The reason for failure is that the change in refractive indices is different from what we expected, which makes the device perform in opposite way. Finally, further suggestions are provided to modify the design so that the device can achieve its expected function.

Label free detection techniques such as surface plasmon resonance, carbon nanotubes, nanowires, and interferometry have been progressing rapidly for biosensing applications. Surface plasmon resonance is considered one of the most promising label free optical techniques. The use of nanohole arrays in a metal film allows for extraordinary transmission and has been motivated by their application as biosensors. Nanohole arrays present several advantages like smaller foot print, dense integration, lower limits of detection, and collinear optical detection. This thesis presents the design parameters for the optimization of sensitivity and resolution of nanohole arrays for refractive index sensing. A systematic study is provided of the influence of the nanohole array periodicity, diameter, and gold thickness. Focused ion beam was used to fabricate the nanohole arrays. A microfluidic device with a set of embedded nanohole arrays was developed and used to measure the sensing characteristics. The results are encouraging for potential future biosensing tests. / Graduate

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.