Amorphous and crystalline silicon nanocomposites have been shown to act as effective “sensitizers” for erbium ions. In the present work, a series of erbium-doped (0.2 at.%) SiOx:Er films (x = 1 - 1.8) were synthesized by physical vapor deposition and subsequently annealed at temperatures ranging from 400°C to 1100°C to induce phase separation and cluster growth. Silicon nanocluster (Si-NC) and Er3+ photoluminescence intensity spectra and dynamics were investigated as a function of SiOx composition, annealing temperature, pump wavelength and power, and specimen temperature in order to determine characteristic cross-sections and to map the efficiency of the energy transfer process between Si-NCs and Er3+ ions. Additionally, two types of optical waveguides based on SiOx:Er materials were fabricated using conventional CMOS compatible microfabrication processes. Waveguide propagation losses as well as signal absorption and enhancement were investigated under pumping conditions to evaluate the use of SiOx:Er materials as amplifying media. / Communications and Signal Processing

This thesis describes the design, fabrication and characterisation of an infrared optical waveguide phase modulator. The modulator was fabricated in GaAs utilizing a carrier-concentration-reduction rib waveguide structure with a Schottky diode contact to allow the application of an electric field across the waveguide region. Measurements of the phase modulation are presented with results agreeing with the theoretical predictions of an electrooptic coefficient of 1.2 x 10-12 m/V at 1.15 //m. Fabrication techniques and problems are thoroughly discussed. The second part of this thesis consists of measurements of the quantum confined stark shift in an AlGaAs-GaAs multiple quantum well p-i-n diode structure. The results show useful changes in absorption with applied electric field. Transmission measurements as a function of applied field are presented for TE polarized light in a waveguiding geometry as well as photocurrent measurements in the same geometry and with light incident perpendicular to the MQW layers. Reasonable agreements for the relative field induced shifts of the excitonic feature are found but the absolute position of the feature is blue shifted by 7 meV with respect to the theoretically predicted position. / Thesis / Master of Engineering (ME)

The analogy of optical system to other physical systems has been attracting much attention over the past decades. In coupled optical lattices, phenomena originated from electronic systems, such as Bloch oscillations, Dynamic localization and Zener tunneling, have been extensively investigated and led to novel research directions and applications. Following this idea, harmonic oscillations are spatially mimicked by the propagation of supermodes in quadratically-coupled waveguide arrays. By analyzing the field envelope with the propagation constants and the superposition of the supermodes, we achieve conjugate-imaging at the half-period plane and self-imaging at the full-period plane, which give rise to the linear switching. Combining the linear switching and the nonlinear light propagation triggered at high power level, we demonstrate the superior performances of nonlinear power switching compared with traditional nonlinear directional couplers. Through the linear and nonlinear observation on AlGaAs waveguide array, we present the first experimental proof of the harmonic oscillations in optical waveguide arrays.

The analogy of optical system to other physical systems has been attracting much attention over the past decades. In coupled optical lattices, phenomena originated from electronic systems, such as Bloch oscillations, Dynamic localization and Zener tunneling, have been extensively investigated and led to novel research directions and applications. Following this idea, harmonic oscillations are spatially mimicked by the propagation of supermodes in quadratically-coupled waveguide arrays. By analyzing the field envelope with the propagation constants and the superposition of the supermodes, we achieve conjugate-imaging at the half-period plane and self-imaging at the full-period plane, which give rise to the linear switching. Combining the linear switching and the nonlinear light propagation triggered at high power level, we demonstrate the superior performances of nonlinear power switching compared with traditional nonlinear directional couplers. Through the linear and nonlinear observation on AlGaAs waveguide array, we present the first experimental proof of the harmonic oscillations in optical waveguide arrays.

Long path optical waveguides can be used in optical absorption measurements to increase the optical path length and, thus, the overall absorption of a sample. Recently, 1m long coiled Liquid Waveguide Capillary Cells (LWCC) have been used by analytical spectroscopists to measure the absorption strength of weakly absorbing liquids. However, most of these measurements have used conventional light sources such as Xenon or Halogen lamps and not spectroscopic laser sources. In this thesis study, we used a LWCC absorption waveguide and a laser light source to measure, for the first time to our knowledge, the optical transmission through several water or liquid samples. It was found upon using the LWCC waveguide, the coherent laser light source tended to produce larger variability (>±15%) in the measurements of transmission readings than that for a conventional absorption cell or a conventional light source. This was especially evident when the LWCC waveguide was chemically cleaned with an acid and a base solution between each sample run as directed by the manufacturer. The non-coherent optical sources, Halogen lamp and Xenon arc lamp, produced more stable (±3%) transmission measurements. Finally, using a Helium Neon laser scattered off a diffuse reflecting surface was found to produce moderate variability (±7%), but this was much less than the coherent Helium Neon laser alone. It was concluded that the use of the coherent source was more susceptible than the non-coherent source to small changes in the reflectivity or index of refraction along the wall of the coiled LWCC waveguide. Our results are consistent with recent work by Barwicz and Haus, and by Lytle and Splawn who saw a large dependence of the transmission through a hollow straight waveguide upon changes in the polarization and input angle of the laser beam directed into the waveguide.

In this thesis, the characteristics and the applications of Kerr-like nonlinear optical waveguide structures have been studied. The nonlinear optical waveguide is a medium whose refractive index changes with the electric field intensity. In the characteristics of Kerr-like nonlinear optical waveguide structures, we propose a general method for analyzing the three-layer optical waveguide structure with all nonlinear layers by using modal theory. Based on this method, the analysis of transforming arbitrary nonlinear layer into linear layer can be achieved easily by modifying nonlinear coefficient. All kinds of the transverse electric field distributions and the dispersion relation in the three-layer Kerr-like nonlinear optical waveguide structure have been obtained. In the application of Kerr-like nonlinear optical waveguide structures, the Mach-Zehnder waveguide interferometer structure will be discussed. Based on the asymmetric medium and asymmetric construction, the new all-optical router switching device and dense wavelength division multiplexing device have been proposed. The numerical results show that the proposed structures could function as all-optical switch devices and all-optical dense wavelength division multiplexing device.

The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator with simple fabrication process. A 1.49

Abstract¡G Scalar coupled mode theory predicts that the output powers at two nonlaunch fibers are identical for the equilateral 3x3 fiber couplers due to the geometrical symmetry, but several experimental results demonstrate that they are not equal. In this work, a power coupling model with considering the polarization property of input power is proposed for the equilateral 3x3 fiber couplers. Consistent with the measurement results, the model shows that when a polarized light is launched into one of the three fibers the output powers at the other two nonlaunch fibers are unequal.

This research proposes a novel polymer-based optical waveguide made with Polydimethylsiloxane (PDMS) for optical detection applications. Alternative to other fiber-based sensor, the proposed optical sensor uses PDMS waveguide as the main sensing component. PDMS has excellent optical properties which is essential for bio-photonic detection, including highly optical transparency, good flexibility and high bio-compatibility. Uncured PDMS polymer is cast in a Teflon tubing to form the PDMS rod. Since the reflective index of PDMS is as high as 1.43, that the bare PDMS can be an optical waveguide while the reflective index of the surrounding media is smaller than 1.43. The cast PDMS waveguide is then connect with plastic optical fibers to form the proposed optical waveguide system. In order to improve the optical performance of the PDMS waveguide, a surface coating process is used to reduce the surface roughness of the PDMS waveguide. The measured insertion loss with and without performing the surface coating procedure is 1.14 and 1.71dB/cm, respectively. Once the PDMS waveguide is formed, Au nanoparticles (Au-Nps) were coated on the PDMS surface with the assistance of a positive charge polymer of PDDA to form an optical waveguide capable of localized SPR detection. In addition, an atmospheric plasma treating process is used to enhance the coating ratio and speed of Au-Nps. UV-VIS spectrum and the SEM observation of the Au-particle coated PDMS waveguide confirm that the plasma treatment process significantly improves the coating results of Au-Nps. Liquid samples with different refractive index were used to demonstrate the LSPR sensing ability of the fabricated optical waveguide. The label free DNA detection was demonstrated by the system. The thiolated single strand DNA was modify on the PDMS optical waveguide as a DNA probe and bound with target DNA by DNA hybridization. The detection limit is as low as 10 pM. This research provides a simple and fast fabrication method to fabricate waveguide-based LSPR sensors.

Integrated optics present a potentially low cost and higher performance alternative to electronics in optical communication systems. Surface plasmon waveguides (SPWGs) offer a new approach for manipulating light in integrated optical chips. SPWGs provide several advantages over dielectric waveguides. In this study, a fabrication process for SPWGs is developed. SPWGs are fabricated with various lengths and bend radii to allow for study of absorption and bending losses in the waveguides at telecommunications wavelengths (~1550nm). Finite-element method models of straight, bent, and optically coupled waveguides are developed and analyzed.