No description available.

No description available.

No description available.

We have developed a rigorous leaky-mode analysis on the antiresonant reflecting optical waveguides (ARROW¡¦s) using a so-called ¡§coupled electric (CE) coupled magnetic (CH) field method.¡¨ Radiation loss characteristics and the field distribution of the ARROW are analyzed in detail. Meanwhile, both the refractive indices and the thickness dependence for the isolation and distinction of modes are also investigated in this thesis. From the CE¡VCH method, the associated complex symmetric tridiagonal matrices are derived to solve the modal solutions via the eigenvalue-eigenvector technique. The uniquely designed formulation of CE¡VCH method yields better numerical properties, specifically in calculating the field distribution. This is suitable for any combination of materials and is capable of handling complex problems such as the leaky characteristics for both lossless and lossy cases. To quickly solve the complex roots of the ARROW, a set of accurate closed-form approximations for estimating both the field distribution and complex propagating constant have been derived from the CE¡VCH matrices. These first-order approximations provide six significant figures of the real part of the propagation constant

Many waveguide components in the integrated optics are built with bending structures, such as Y-branches, couplers, tapered waveguides, etc. The bending angles are getting larger and larger in order to fill into a smaller integrated optical circuit. The influences of wide bending angles are no longer ignorable. Commercially available beam-propagation method (BPM) design tools are inadequate for simulating and optimizing the problem we consider. These include tightly curved waveguide sections, reflection/transmission from slanted end facets and U-turn reflectors. In this thesis, we applied the coupled transverse-mode integral-equation (CTMIE) formulation and mode matching method to study the field distribution in a 2-dimentional rectangular waveguide structure with perfect boundary conditions. The problem is first separated into parts and then converted into a block-diagonal matrix equation. By considering the symmetry of the bending structures, the original problem is broken down to two smaller problems each with it¡¦s own boundary conditions. The combined solutions provide the desired results.

A BCB Polymer/Ta2O5/SiO2 antiresonant reflecting optical waveguide (ARROW) at quasi-antiresonant condition is presented. The waveguide consists of the SiO2 second cladding, the Ta2O5 first cladding, and the BCB core. The lateral guiding of the ARROW waveguide was formed by reactive ion etching based on SF6 and O2 mixtures (SF6 : O2 =1.5 : 1). A metal layer Ni/Cr thin films were used as the etch mask to avoid cracking of the mask caused by large thermal expansion coefficient of the BCB Polymer. The waveguide losses were measured by the cut back method. Large dry-etching aspect ratio of the BCB polymer to the etch mask was obtained. For TE polarized light, the propagation loss of the waveguide was 1.12 dB/cm at 1.3£gm. The propagation loss for TM polarized light was 2.56 dB/cm.

Polymer based optical waveguides on silicon substrate were fabricated and the characteristics of the polyimide used were investigated. The optical waveguides were designed according to the simulation results calculated by beam propagation method. The fabrication began with spinning and curing two polyimide materials as the cladding and the core layers on silicon substrate. The refractive index of polyimide was obtained by prism coupling system. The index contrast was 0.67 % and the waveguide was the ridge type structure obtained by reactive ion etching process. Then a top cladding was spun on the sample and cured to complete the waveguide fabrication. Finally, the propagation loss of the TE mode of the waveguides was measured by using cut-back method. The loss was 2.4 dB/cm.

R-matrix theory has been used to analyze a variety of scattering potentials in ballistic electron waveguides. The S-matrix is the principal result of this method. Here we analyze ballistic electron scattering in a 1D waveguide with a step potential at its terminus using Green’s function theory. We calculate the S-matrix for this system, scattering particles’ quasibound states, and the survival probability of a particle initially localized in the step region. We then apply R-matrix theory to the same problem. In doing so, we demonstrate the versatility of the Green’s function approach, but also its relative complexity. / text

Ringdown spectroscopy (RDS) is an absorption spectroscopic and detection technique that makes use of an optical cavity to realize a long effective pathlength through a sample and to render the measurement independent of intensity. These two features give RDS an advantage over traditional absorption techniques and allows its application in measuring concentrations of strongly absorbing analytes present in trace amounts, or in measuring weak absorptions for analytes in higher concentrations. The resonant optical cavities used here are created from optical fibre. This permits the easy construction of an inexpensive apparatus for RDS. The performance of various cavity geometries (linear, circular) in three ranges of the visible and near infrared spectrum (405, 800, and 1550 nm) was examined. Concurrent multiexponential decays arising from core modes, cladding modes, and amplified spontaneous emission were analyzed in the framework of an exponential decay model transformed into the frequency domain. The small mode field diameter of light within a fibre is well suited to probing very small liquid volumes on the order of pico- or femtolitres. This uniquely positions optical waveguide-based RDS for application in absorption detection for separation techniques such as capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) where high time resolution detection is required across narrow separation channels. The experimental and theoretical work presented here was preformed with an eye towards this purpose. / Thesis (Master, Chemistry) -- Queen's University, 2007-07-04 16:23:53.173

No description available.