Characterisation of stripe optical waveguides fabricated by silicon impurity induced disordering of GaAs/AlGaAs MQW material.

Impurity Induced Layer Disordering (IILD) of a GaAs/AlGaAs Multi Quantum Well (MQW) structure is known to produce a change in the refractive index dependent on the polarisation of the propagating mode. This index change can be used to provide lateral confinement in stripe optical waveguides, which are an essential component in any integrated optical circuit. Silicon implantation has been used to disorder GaAs/AlGaAs MQWs and the effects of implantation dose, encapsulant and annealing conditions on the disordering process have been investigated using Photoluminescence (PL). It was observed that deep level emissions accompanied the disordering and the results suggest that the degree of intermixing and the deep level emissions were determined by several competing processes. Calculation of the deep level/band-edge integrated intensity ratio for these emissions, provided an indication of the suitability of the process for the fabrication of disorder delineated stripe waveguides, where a correlation between the propagation loss of the waveguides and the integrated intensity ratio was observed. Buried stripe optical waveguides fabricated using Si+ IILD has been demonstrated for the first time in this work. Waveguide assessment using end-fire coupling was performed with the propagation losses and modal dimensions determined. The lowest loss of a waveguide fabricated by IILD presented in this thesis is 21.9dBcm-1 and it is suggested that the deep level states observed using PL are a significant source of attenuation of the propagating mode in the side walls of the waveguides