Acoustics is a vast subject that has been utilised in many forms for millennia. Recent work has, amongst other things, explored the control of sound using geometric structure to complement inherent material properties. In this thesis, structured plates and surfaces are exploited to engineer specific acoustic responses. The acoustic transmittance and reflectance of these systems is explored in air and underwater to further understanding and develop structures that possess tailored acoustic properties. Original investigations are presented across six chapters. The first three investigations explore the transmittance of periodically perforated plates in air. The fourth investigation considers a non-resonant mechanism of obtaining complete transmission by varying the fluid environment and the fluid in the apertures of a periodically perforated plate is explored. The fifth investigation considers the transmittance through a slit in an acoustically soft plate underwater. Finally, the surface waves supported on periodically structured surfaces are explored by observing the reflectance of the surface. An acoustic field incident upon a perforated plate is partly transmitted. However, at frequencies dictated by the thickness of the plate, the acoustic field is completely transmitted. Stacking two plates with a small separation creates a resonant cavity between the plates that is the origin of a narrow acoustic stop-band at the frequency of the resonance. By varying the offset of the stacked plates and by varying the gap between the plates the frequency of this acoustic stop band is controlled. Altering the geometry of the plate surface within the gaps allows the gap to behave like an array of Helmholtz resonators, in doing so the frequency of the acoustic stop-band is significantly lowered. Varying the acoustic properties of the fluid contained within the apertures of a periodically perforated plates changes how sound is transmitted through the structure. By careful choice of the fluid environment and aperture media, it is demonstrated numerically that broadband total transmittance can be obtained. Acoustic tunnelling is demonstrated through an acoustically soft-walled slit underwater. The slit exhibits a cut-off frequency below which no propagating waves can exist, in contrast to a rigid-walled slit where propagating waves exist down to zero frequency. Resonant acoustic tunnelling is observed through two closely spaced slits in a series connection, at a frequency below the cut-off frequency of the lowest supported propagating mode. A preliminary study of pseudo surface acoustic waves on periodically structured surfaces observes the excitation of surface waves in reflection. A long pitch grating, added to the surface allows diffractive coupling of incident acoustic radiation to the surface wave. However, the height of the grating above the sample is shown to strongly affect the frequency at which the surface wave is detected. All the structures investigated may be designed to provide a desired response by careful choice of the geometry and materials.

Terahertz (THz) frequencies comprise the portion of the electromagnetic spectrum more energetic than microwaves, but less energetic than infrared light. The THz band presents many opportunities for condensed matter physics and optics engineering. From the physics perspective, advances in the generation and detection of THz radiation have opened the door for spectroscopic studies of a range of solid-state phenomena that manifest at THz frequencies. From an engineering perspective, THz frequencies are an under-used spectral region, ripe for the development of new devices. In both cases, the challenge for researchers is to overcome a lack of sources, detectors, and optics for THz light, termed the THz Gap. Metamaterials (MMs), composite structures with engineered index of refraction, n, and impedance, Z, provide one path towards realizing THz optics. MMs are an ideal platform for the design of local EM field distributions, and far-field optical properties. This is especially true at THz frequencies, where fabrication of inclusions is easily accomplished with photolithography. Historically, MM designs have been based around static configurations of resonant inclusions that work only in a narrow frequency band, limiting applications. Broadband and tunable MMs are needed to overcome this limit. This dissertation focuses on creating tunable and controllable MM structures through the manipulation of electromagnetic interactions between MM inclusions. We introduce three novel MM systems. Each system is studied computationally with CST-Studio, and experimentally via THz spectroscopy. First, we look at the tunable transmission spectrum of two coupled split ring resonators (SRRs) with different resonant frequencies. We show that introducing a lateral displacement between the two component resonators lowers the electromagnetic coupling between the SRRs, activating a new resonance. Second, we study an SRR array, coupled to a non-resonant closed ring array. We show that lowering the interaction strength through lateral displacement changes the MM oscillator strength by ~ 40% and electric field enhancement by a factor of 4. Finally, we show that interactions between a superconducting SRR array and a conducting ground plane result in a temperature and field strength dependent MM absorption. The peak absorption changes by ~ 40% with increasing electric field and by ~ 66% with increasing temperature.

This thesis presents novel results in the field of plasmonics and optoelectronics application. Plasmonics is the rapidly expanding branch of photonics. It opens up capabilities of electronic and photonic device implementation within the same integrated circuits as well as enhances the limit of detection for chemical and biological-based sensors. The first finding lies in solving the dilemma in search of ultimate plasmonics materials for plasmonics application. It is well known that Cu and Ag are metals that have incredible electric and optic properties. However, they are easily oxidized in contact with air. Both experimental and theoretical findings demonstrate that application of a mono or bilayer graphene protects Cu and Ag from oxidation and degradation of its plasmonic properties. The performance of each metal is evaluated based on the quality factor Q and the minima in amplitude of reflection intensity Rmin of the Surface plasmon-polariton (SPP) curve. The second novelty of this thesis comprises the fabrication of low loss, high efficient broadband, as well as narrowband, graphene-based electro-absorption modulators. The studied graphene-based modulators made use of Fabry-Perot resonator geometries. It has been shown that high-k dielectric hafnium dioxide (HfO2) provides solid state “supercapacitor” effects and allows to observe light modulation from the near-infrared to shorter wavelengths close to the visible spectrum with remarkably low gate voltages (~4 V). The electro-absorption modulators based on Fabry-Perot resonator geometry reached the modulation depth in transmission mode of 28% at a wavelength of 1.1 Âμm.

Chen, Mengyu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 110-116). / Abstracts in English and Chinese. / Abstract --- p.I / Acknowledgments --- p.V / Table of Contents --- p.VI / List of Tables and Figures --- p.VIII / List of Abbreviations and Symbol --- p.XII / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Left-handed material --- p.1 / Chapter 1.1.1 --- Left-handed transmission --- p.1 / Chapter 1.1.2 --- Corrected physical laws and sub-wavelength imaging --- p.4 / Chapter 1.1.3 --- Methods to realized Left-handed Material --- p.5 / Chapter 1.2 --- The meaning of this work --- p.8 / Chapter 1.3 --- Organization of the thesis --- p.8 / Chapter Chapter 2: --- Basic theory and Metamaterial Devices --- p.11 / Chapter 2.1 --- Left-handed Metamaterials --- p.11 / Chapter 2.1.1 --- Metal wire arrays structure --- p.11 / Chapter 2.1.2 --- SRR structure --- p.14 / Chapter 2.1.3 --- SRR plus wire arrays structure --- p.20 / Chapter 2.1.4 --- Development and Fishnet structure --- p.22 / Chapter 2.2 --- Transmission line model --- p.26 / Chapter 2.2.1 --- Transmission line theory --- p.26 / Chapter 2.2.2 --- Transmission line model of SRR plus wire arrays structure --- p.27 / Chapter 2.2.3 --- Transmission line model of Fishnet structure --- p.29 / Chapter 2.3 --- Electric Metamaterial Devices --- p.32 / Chapter 2.3.1 --- The dielectric property of SRR --- p.32 / Chapter 2.3.2 --- Active Metamaterial Devices --- p.34 / Chapter 2.4 --- Other Metamaterial Devices --- p.36 / Chapter 2.4.1 --- Metamaterial Electromagnetic Cloak --- p.36 / Chapter 2.4.2 --- Metamaterial based Perfect absorber --- p.39 / Chapter 2.5 --- Homogenization and effective material parameters --- p.40 / Chapter Chapter 3: --- Metamaterial devices fabrication --- p.43 / Chapter 3.1 --- Introduction --- p.43 / Chapter 3.2 --- Photolithography --- p.44 / Chapter 3.2.1 --- Process description --- p.45 / Chapter 3.2.2 --- Parameter Selection --- p.50 / Chapter 3.3 --- E-beam Evaporation and lift-off --- p.51 / Chapter 3.3.1 --- E-beam evaporation --- p.51 / Chapter 3.3.2 --- Lift-off --- p.53 / Chapter 3.4 --- Flexible metamaterial and double-layer device --- p.54 / Chapter 3.4.1 --- Polyimide brief introduction --- p.54 / Chapter 3.4.2 --- Double-layer structure and fabrication --- p.57 / Chapter Chapter 4: --- Simulation and Experiment Method --- p.61 / Chapter 4.1 --- Numerical simulation methods and software --- p.61 / Chapter 4.1.1 --- Time domain solver --- p.61 / Chapter 4.1.2 --- Frequency domain solver --- p.62 / Chapter 4.2 --- High Frequency Structure Simulator (HFSS) --- p.63 / Chapter 4.2.1 --- Introduction --- p.63 / Chapter 4.2.2 --- Simulation Process --- p.64 / Chapter 4.2.3 --- Parameter Retrieve Method --- p.67 / Chapter 4.3 --- Terahertz Time Domain spectroscopy system --- p.71 / Chapter 4.3.1 --- Introduction --- p.71 / Chapter 4.3.2 --- System Setup --- p.73 / Chapter 4.3.3 --- Photoconductive Antennas --- p.75 / Chapter 4.3.4 --- Data Analysis Method --- p.77 / Chapter Chapter 5: --- Simulation and Experiment Results and Analysis --- p.82 / Chapter 5.1 --- SRR structure based Metamaterial Devices --- p.82 / Chapter 5.1.1 --- SRR based left-handed material --- p.82 / Chapter 5.1.2 --- Electric Metamaterial Devices with different substrate --- p.84 / Chapter 5.2 --- Fishnet structure based metamaterial devices --- p.94 / Chapter 5.2.1 --- Dual-band Polarization-Insensitive Left-handed Metamaterial --- p.94 / Chapter Chapter 6: --- Conclusion --- p.106 / Chapter 6.1 --- Conclusion and potential application --- p.106 / Chapter 6.2 --- Future work --- p.108 / References --- p.110 / Publication list --- p.116

La miniaturización de componentes de microondas es uno de los retos de los dispositivos de comunicación actuales y futuros. Por esta razón, esta tesis está orientada al estudio de nuevas estrategias de miniaturización de componentes planares de microondas no radiativos. A lo largo de este trabajo, se han aplicado diferentes técnicas de miniaturización para el diseño de diversos componentes de microondas como dispositivos multi-banda o filtros, incluyendo también implementaciones eléctricamente reconfigurables. Para obtener esta compactación de tamaño requerida y/o funcionalidad multi-banda, se proponen nuevas líneas artificiales basadas en los resonadores semi-discretos open split ring resonators (OSRRs) y open complementary split ring resonators (OCSRRs). De esta forma, se presentan nuevas líneas de transmission compuestas zurdo diestras (composite right-left handed o CRLH) aplicándose al diseño de inversores de impedancia, divisores de potencia y filtros paso banda de banda ancha. Adicionalmente, mediante la combinación de estos resonadores con componentes semi-disctretos adicionales, se presentan líneas CRLH extendidas (E-CRLH) y se aplican a la implementación de inversores de impedancia, divisores de potencia y híbridos en cuadratura con funcionalidad en cuatro bandas (quad-band), así como filtros paso banda de banda dual. Para demostrar y validar su funcionalidad, se implementan y fabrican diferentes demostradores de prueba de concepto para todos los dispositivos anteriormente mencionados, obteniendo un buen ajuste entre las simulaciones y la medida. Además, también se presentan los modelos circuitales, así como la metodología de diseño basada en el método de extracción de parámetros. A través de este método, se demuestra que los modelos circuitales proporcionan una descripción precisa de las estructuras consideradas. También se estudia la reconfigurabilidad de las líneas CRLH presentadas considerando sustratos ferroeléctricos, específicamente titanato de bario estroncio (barium-strontium-titanate o BST). Mediante esta técnica, se demuestra la reconfigurablidad de estas líneas CRLH, obteniendo un rango de sintonía simulada y medida del 36.6%. Una vez experimentalmente validada esta técnica, se dota de reconfigurabilidad a los componentes mono banda y de banda dual basados en líneas CRLH previamente presentados, explorando tanto la metodología como sus limitaciones. Finalmente, también se presentan nuevos filtros compactos con respuestas abruptas basados en los resonadores de salto de impedancia (stepped-impedance-resonators o SIRs) acoplados a una línea de transmisión coplanar. Tras analizar el resonador aislado y su modelo circuital, se diseñan filtros elípticos paso bajo y paso alto, así como filtros paso banda con ceros de transmisión mediante la teoría de filtros convencional, obteniendo estructuras con un alto grado de compactación y buena funcionalidad. / The miniaturization of microwave components is one of the challenges of present and future communication devices. For this reason, this thesis is focused on the study of new miniaturization strategies for planar non-radiating microwave components. Throughout this work, different miniaturization approaches have been applied to the design of several microwave components such as multi-band devices and filters, including also electronically tunable implementations. To obtain the required compact sizes and/or multi-band functionality, new artificial lines based on the semi-lumped open split ring resonators (OSRRs) and open complementary split ring resonators (OCSRRs) are proposed. Firstly, composite right-/ left-handed (CRLH) transmission lines are presented, applying such lines to the design of dual-band impedance inverters and Y-junction power dividers, as well as wideband band-pass filters. In addition, by combining these resonators with additional semilumped components, extended composite right-/left-handed (E-CRLH) transmission lines are also reported and applied to implement quad-band impedance inverters, power dividers, branch-line couplers and dual-band band-pass filters. To demonstrate and validate its functionality, different proof-of-concept demonstrators for all the aforementioned devices are implemented and fabricated, where a good agreement between simulations and measurement is obtained. Furthermore, the circuit models and the design methodology for all the presented devices are also reported, based on a parameter extraction method. Through this method it is demonstrated that the circuit models provide an accurate description of the considered structures. The tunability of such CRLH lines is also analyzed by means of barium-strontiumtitanate (BST) thick-films. With this approach, a tunable CRLH line with simulated and measured tunability range of 36.6% is demonstrated. Once this approach is experimentally validated, the previously presented mono-band and dual-band components based on the CRLH lines are provided with this tunability, exploring both its methodology and limitations. Finally, new compact filters with sharp responses are also presented based on stepped-impedance-resonators (SIRs) coupled to coplanar waveguide (CPW) host transmission lines. After analyzing the isolated resonator and its circuit model, elliptictype low-pass and high-pass filters, as well as band-pass filters with transmission zeros are designed through the conventional filter theory, where a high-degree of compactness as well as good performance is demonstrated.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 74-78). Also available on the World Wide Web.

Thesis (M.S.)--California Polytechnic State University, 2008. / "June 2008." "In partial fulfillment of the requirements for the degree [of] Master of Science in Electrical Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Dean Arakaki, Ph.D. Includes bibliographical references (leaves 146-148). Also available online and on microfiche (2 sheets).

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed May 27, 2009). Graduate School of Engineering, Dept. of Electrical and Computer Engineering. Includes bibliographical references (p. 127-140).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 121-129). Also available in electronic version.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 75-82). Also available on the World Wide Web.