This thesis focuses on the characterization and optimization of microwave power transistors using a commercial on-wafer harmonic load pull system. Specific attention is paid to the output tuning of the second harmonic impedance presented to the device. The ability to quantify the level of accuracy in a load pull system is explored by using various calibration validation methods, including a method called Delta-Gt. In this work experiments and simulation comparisons are described for three different device technologies, namely GaAs pHEMT, GaAs HJFET and InGaP HBT. Externally supplied non-linear models were used for the simulations and these were exercised and compared against 2.45 GHz fundamental frequency measurements made as part of this work to first validate the models against IV, S-Parameter and fundamental load-pull data and finally to explore performance variations under 2nd harmonic impedance tuning. The measured harmonic load-pull data pointed to different guidance on how one would match the 2nd harmonic for best performance. With regard to the model validation/assessment work it was found that only in the case of the pHEMT did the available non-linear model provide a good fit to all the different types of measurement data, including 2nd harmonic tuning data. This model was then used to show that even though the 2nd harmonic tuning measurement had a limited maximum reflection coefficient of about 0.8. Simulated results showed that the worst case linearity condition occurred for the same reflection angle as that measured, but that the variation between worst-case and best case linearity under 2nd harmonic tuning grows considerably larger as the magnitude of the 2nd harmonic reflection coefficient approaches 1. A key aspect of the methodology presented in this work is that once a non-linear model is proved to be valid for harmonic tuning conditions it can be used to explore harmonic tuning-related design trade-offs under a much wider range of frequency and tuning conditions than can be practically explored with measurements alone.

The primary target of this paper is to fabricate triplexer modules based on Si-bench technology. The triplexer modules were formed by hybrid integration of single mode lensed fibers and ultra-thin thin-film filters (TFF) on silicon bench as using V-groove and U-groove techniques. The output light at 1.31 µm was launched into the input lensed fiber of the module. After passing through two filters, the light was received by the output lensed fiber of the module. The insertion loss of the module at the 1.31 µm light was 1.25 dB. On the other hand, incoming lights at 1.49µm and 1.55µm were received from the output lensed fiber. Lights at 1.49µm will pass through the first filter, and be reflected by the second filter, and eventually be collected into the second multimode fiber. The insertion loss of the module at the 1.49 µm light was 1.14 dB. The 1.55µm wavelength lights received at the lensed fiber are reflected by the first filter and collected by the first multimode fiber. The insertion loss of the module at the 1.55 µm light was 0.68 dB.

<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)

Optical devices based on planar lightwave circuit (PLC) technology have the advantages of small size, high reliability, possibility for large scale production, and potential integration with electronics. These devices are widely employed in optical telecommunications, sensing, data storage, imaging, and signal processing. This thesis focuses on some selected PLC based devices, such as power splitters, demultiplexers, triplexers and polarization beam splitters. First, the basic principle of the waveguides and the simulation methods for PLC devices are discussed. A novel effective index method is introduced to reduce a two-dimensional structure to a one-dimensional one, and can be implemented for arbitrarily shaped waveguides. Numerical methods, such as finite-difference mode solver, beam propagation method, finite-difference time-domain method are introduced to analysis the mode profile of the waveguides, and the propagation properties of light in PLC devices. Multimode interference (MMI) couplers are widely used in many PLCs, such as power splitters, ring lasers, optical switches, and wavelength division multiplexers/demultiplexers. In this work, concepts for improving the self-imaging quality of MMI couplers are analyzed and new designs are proposed. A significant improvement in performance together with compact sizes were obtained with taper sections at the input/output of MMI couplers based on SOI, and deeply etched ridges in MMI couplers based on SiO2. A polarization insensitive dual wavelength demultiplexer based on sandwiched MMI waveguides was presented. Novel devices including triplexers and polarization beam splitters were realized by using photonic crystal (PhC) structures. Two stages of directional couplers based on PhC waveguides are cascaded to form an ultracompact triplexer. The special decoupling property of the PhC waveguide based directional coupler was utilized in the design. A novel polarization beam splitter was realized by combining a MMI coupler and a PhC which works as a polarization sensitive reflector. Finally, fabrication and optical characterization of an ultra-compact directional coupler and PhC structures in InP are presented. In a single etching step, by using the lag-effect in inductively coupled plasma reactive ion etching, a compact directional coupler (55 μm) is demonstrated. Carrier life times in PhC structures etched by chemically assisted ion beam etching were investigated, for emitter and switching applications. / QC 20100909