Impedance Transformers

Non

Modelling and Characterization of Guiding Micro-structured Devices for Integrated Optics

In this thesis we show several modelling tools which are used to study nonlinear photonic band-gap structures and microcavities. First of all a nonlinear CMT and BPM were implemented to test the propagation of spatial solitons in a periodic device, composed by an array of parallel straight waveguides. In addition to noteworthy theoretical considerations, active functionalities are possible by exploiting these nonlinear regimes. Another algorithm was developed for the three-dimensional modelling of photonic cavities with cylindrical symmetry, such as microdisks. This method is validated by comparison with FDTD. We also show the opportunity to confine a field in a region of low refractive index lying in the centre of a silicon microdisk. High Q-factor and small mode volumes are achieved. Finally the characterization of microdisks in SOI with Q-factor larger than 50000 is presente

Numerical modelling of optical micro-cavity ring resonators for WDM networks

Augmenting the level of integration for a lower cost and enhancing the performance of the optical devices have turned out to be the focus of many research studies in the last few decades. Many distinct approaches have been proposed in a significant number of researches in order to meet these demands. Optical planar waveguides stand as one of vital employed approach in many studies. Although, their low propagation loss, and low dispersion, they suffers from high power losses at sharp bends. For this reason, large radius of curvature is required in order to achieve high efficiency and compromise the high level of integration. For the purpose of this research, in this thesis different ways to improve the performance of optical microcavity ring resonators (MRRs) have been thoroughly investigated and new configurations have been proposed. The Multiresolution Time Domain (MRTD) technique was further developed and employed throughout this thesis as the main numerical modelling technique. The MRTD algorithm is used as a computer code. This code is developed and enhanced using self built Compaq Visual Fortran code. Creating the structure and Post-processing the obtained data is carried out using self built MATLAB code. The truncating layers used to surround the computational domain were Uniaxial Perfectly Matched Layers (UPML). The accuracy of this approach is demonstrated via the excellent agreement between the results obtained in literature using FDTD method and the results of MRTD. This thesis has focused on showing numerical efficiency of MRTD where the mesh size allowed or the total number of computed points is about half that used with FDTD. Furthermore, the MRR geometry parameters such as coupling gap size, microring radius of curvature, and waveguide width have been thoroughly studied in order to predict and optimise the device performance. This thesis also presents the model analysis results of a parallel-cascaded double-microcavity ring resonator (PDMRR). The analysis is mainly focus on the extraction of the resonant modes where the effect of different parameters of the structure on transmitted and coupled power is investigated. Also, accurate analysis of 2D coupled microcavity ring resonator based on slotted waveguides (SMRR) has been thoroughly carried out for the purpose of designing optical waveguide delay lines based on slotted ring resonator (SCROW). The SCROW presented in this thesis are newly designed to function according to the variation of the resonance coupling efficiency of a slotted ring resonators embedded between two parallel waveguides. The slot of the structures is filled with SiO2 and Air that cause the coupling efficiency to vary which in turn control both the group velocity and delay time of SCROW structures results from the changing the properties of the bent slotted waveguide modes which strongly depends on the slot’s position. Significant improvements on the quality factor and greater delay time have been achieved by introducing sub-wavelength-low-index slot into conventional waveguide