Effects of annealing silicon ion irradiated rib waveguides with respect to free carrier lifetime

Abstract

Previously we have reported the effects of silicon ion irradiation on free carrier lifetime and propagation loss in silicon rib waveguides, and simulated net Raman gain based on experimental results. We further extend this work by reporting the effects of thermally treating a silicon irradiated sample with a higher dose and energy than previously reported, which produced a poor trade-off between free carrier lifetime and excess optical absorption prior to thermal treatment. Excess losses greater than 80dB/cm were recorded prior to annealing. After thermal treatment, the sample demonstrated characteristics of excess loss and free carrier lifetime recorded previously in much lower energy and dose silicon ion irradiated samples, suggesting that thermally treating samples could enhance the trade-off between free carrier lifetime and excess loss introduced to the rib waveguides. Raman gain simulations based on the new experimental data are reported and show an increase in net gain over previously reported data, suggesting that higher dose, shallow silicon ion implantation is the most efficient way of optimising the trade-off between lifetime reduction and excess optical absorption in silicon rib waveguides, a proposal in our earlier work. The effects of thermally treating low temperature oxide clad waveguides with respect to free carrier lifetime are also reported. Results show that thermally treating a low temperature oxide clad waveguide can vary the intrinsic lifetime. The results of this investigation as well as a discussion into the possible origin of the lifetime change are given.