Chalcogenide glasses and their use in a wide range of optical, electronic and memory applications, has created a need for a more thorough understanding of material property variation as a function of composition and in geometries representative of actual devices. This study evaluates compositional dependencies and photo-induced structural mechanisms in As-S-Se chalcogenide glasses. An effective fabrication method for the reproducible processing of bulk chalcogenide materials has been demonstrated and an array of tools developed, for the systematic characterization of the resulting material's physical and optical properties. The influence of compositional variation on the physical properties of 13 glasses within the As-S-Se system has been established. Key structural and optical differences have been observed and quantified between bulk glasses and their corresponding as-deposited films. The importance of annealing and aging of the film material and the impact on photosentivity and long term behavior important to subsequent device stability have been evaluated. Photo-induced structures have been created in the thin films using bandgap cw and sub-bandgap femtosecond laser sources and the exposure conditions and their influence on the post-exposure material properties, have been found to have different limitations and driving mechanisms. These mechanisms largely depend on both structural and/or electronic defects, whether initially present in the chalcogenide material or created upon exposure. These defect processes, largely studied previously in individual binary material systems, have now been shown to be consistently present, but varying in extent, across the ternary glass compositions and exposure conditions examined. We thus establish the varying photo-response of these defects as being the major reason for the optical variations observed. Nonlinear optical material properties, as related to the multiphoton processes used in our exposure studies, have been modeled and a tentative explanation for their variation in the context of composition and method of evaluation is presented.

An approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled cavity systems offer the designer slow light propagation which increases photon lifetime, reduces size limitations toward on-chip integration, and offers enhanced light-matter interaction. A unique resonant structure explained by various numerical models enables comb-like resonant clusters in systems that otherwise have no such regular resonant landscape (e.g. photonic crystal cavities). Through design, simulation, fabrication and test, the work presented here is a thorough validation for the future potential of coupled-resonator filters in frequency comb laser sources.

Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or complicated conversions between optical and electrical signals. This dissertation explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths. While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs.

This work analyzes the design and implementation of waveguides used to measure stress waves in solid mechanics via explicit finite element analysis and experimentation. Many areas of physics use waveguides where control of timing, location, or frequency of waves is imperative to functionality of a system. Split Hopkinson pressure bars (Kolsky bars) traditionally utilize straight waveguides during testing. Prior research produced the first bent wave guide for use in such an application, the coaxially embedded serpentine bar (CESB). Explicit finite element analysis (FEA) provides a modeling approach to understand the effects of pass and joint geometry and boundary conditions on the functionality of solid-mechanic waveguides like the CESB. FEA and experimentation also contrasts the functionality of welded joints and threaded joints. Novel waveguide designs that do not feature tubes are also detailed for use in dynamic mechanical testing and dynamic hardness indentation experiments. These designs feature acoustic lengths up to two orders of magnitude greater than their physical lengths.

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<p>Since the inception of integrated electronic circuits there has been a trend of miniaturizing as many electronic, optical and even mechanical circuits and systems as possible. For optical applications this naturally led to the invention of semiconductor optical sources such as the laser diode (LD) and the light emitting diode (LED). A third device, the superluminescent diode was later invented to offer an output with a power similar to that of an LD and spectral width similar to that of an LED. However, there is usually a trade off between the output power and spectral width of the generated beam. The main challenge in the development of SLD is, therefore, finding ways to mitigate the power-spectral linewidth trade off.</p> <p>Previous work has two major directions. In the first one the goal is to eliminate facet reflections thus preventing lasing from happening. The detrimental effect of lasing is that even before it starts the spectral width quickly narrows down. In the second research direction the goal is to make the material gain spectrum wider by playing with different parameters of quantum well active regions.</p> <p>This research work explores yet another way of broadening output spectrum of SLD while allowing the power to increase at the same time. The surface-plasmon waveguide (SPWG) has been proposed to replace the dielectric waveguide, for the first time. A novel SPWG structure is introduced and designed to optimize the device performance in terms of the output power, spectral width and their product known as the power-linewidth product. The effect of different parameters of the new structure on the output light is investigated and attention is given to the high power, high spectral width and high power-linewidth product regimes.</p> / Doctor of Philosophy (PhD)

<p> As the fundamental basic building blocks of photonic circuits, optical waveguide structures play important roles in modem telecommunication and sensing systems. Various structures ranging from the dielectric waveguide utilizing the total internal reflection (TIR) to the more advanced structures based on the surface plasmon polaritions (SPPs) are widely investigated and studied in industrial and research areas. With the fast development of fabrication technologies, more and more complicated structures are predicated to emerge as the requirement of highly integrated photonic circuits. Modeling and simulation methods, as efficient as well as excellent cost performance tools comparing to costly facilities and time-consuming fabrication procedures, are demanded to explore and design the devices and circuits before their finalization. </p> <P> This thesis reports a series of techniques to model two dimensional waveguide structures, including the conventional planar and surface plasmon polariton waveguides. This thesis contains both the methods and their applications to model and investigate the mode and propagation characteristics including the guided waves and the radiative waves. The methods include mode solvers based on fmite difference method (FDM) and complex mode matching method (CMMM), furnished with perfect matching layer (PML) for both guided and radiation modes. Based on the developed techniques, solutions of design of Bragg gratings with deep corrugations are presented; also various surface plasmon polariton (SPPS) grating structures are investigated. </p> / Thesis / Master of Applied Science (MASc)

<p> The modeling, design and simulation of optical waveguides and integrated optical triplexer filters are presented. The work includes two subjects. One is application of improved three-point fourth-order finite-difference method and the other is design of triplexer optical filter for fiber-to-the-home passive optical network.</p> <p> The improved three-point fourth-order finite-difference method utilizes special format of one dimensional Helmholtz Equation and adopts generalized Douglas scheme and boundary conditions matching at interface. The modal analysis of dielectric slab waveguides and metal slab waveguides that support Surface Plasmon Plaritons by using this improved fourth-order finite-difference method is compared by using traditional first-order central difference method. The application of using improved three-point fourth-order finite-difference method in modal analysis of optical fiber waveguide is also provided.</p> <p> The modeling, design and simulation of monolithically integrated triplexer optical filter based on silicon wire waveguide are presented in detail. The design of this device facilitates multi-mode interference device (MMI) and arrayed waveguide grating (AWG) device to function as coarse wavelength division multiplexing and dense wavelength division multiplexing respectively. The MMI is used to separate downstream signs for upstream signal and AWG is used to further separate two down-stream signals with different bandwidths required. This design is validated by simulation that shows excellent performance in terms of spectral response as well as insertion loss.</p> / Thesis / Master of Applied Science (MASc)