Characterisation and efficient simulation of thermal phenomena in SIMOX thermo-optic phase modulators

Silicon can be very effectively exploited in integrated optics due to its well-defined process chemistry and the availability of techniques developed primarily for the semiconductor industry which allow control over dimensions and the creation of arbitrary two dimensional structures with great precision and repeatability. In this thesis the complete design and simulation of thermo-optic phase modulators, realised in silicon-on-insulator (SOI), is presented. Since material thermal and optical parameters vary with temperature, anomalous departure between first-order theory and experimentation can exist when operating under conditions whereby material parameters are markedly different from those experienced at room temperature. A general model for steady-state analysis is developed which, through relevant and justified assumptions, provides solution times far shorter than full finite-difference approaches whilst accounting for temperature-variant material characteristics over the full operating range of the device. For transient analysis, a simple lumped-capacity model is also developed. A selection of modulators with different geometries are fabricated and tested over a broad range of operating conditions, showing the modeling to be robust to variations in ambient temperature, wavelength, material composition and device architecture. Devices optimised for speed are shown to have drive power requirements less than 100mW and have 3dB bandwidths of greater than 45kHz. Where a device has been designed to minimize power requirements, 3dB bandwidths in excess of 1kHz have been achieved for less than 10mW of drive power. A basic set of design parameters is developed which allow estimation of bandwidth and power requirements based on an initial knowledge of the material system and the intended modulator architecture. (author)