Analysis of strain-induced polarisation-insensitive integrated waveguides fabricated using ion-implantation-induced intermixing

The interdiffusion effect on the strain build-up and refractive index profile of lattice-matched InGaAs/InGaAsP multiple quantum wells is reported. Interdiffusion is achieved experimentally using low energy (360 keV) arsenic or phosphorus ion-implantation-induced disordering, followed by an annealing step. A model of the interdiffusion process has been developed to analyse the effect of different interdiffusion ratios on the waveguide's polarisation behaviour through the strain build-up and the refractive index profiles for the transverse electric and transverse magnetic modes. Polarisation-resolved photocurrent absorption measurements of quantum-well waveguide structures have shown that sufficiently high ion implantation doses can lead to the realisation of polarisation-insensitive waveguides at 1.55 mum wavelength operation. Comparison with the modelling results shows that the polarisation-dependent behaviour of the waveguides is best described by a higher interdiffusion ratio for the group V than for the group III atoms.