Numerical study of polarisation-selective side-illuminated pin photodetectors grown on InP substrate for hybridisation on silicon platform

A monolithic polarisation-selective side-illuminated pin photodetector is described using the coupling properties of symmetric and asymmetric slab optical waveguides. First, a basic structure is proposed, analysed and optimised by modal analysis, leading to a computed polarisation ratio of 15.7 dB. Then the symmetric waveguide is replaced by a multimode diluted waveguide optimised by a genetic algorithm coupled to a beam propagation method. This significantly improves the performance of the device and particularly the computed polarisation ratio, which reaches 21 dB. This InP-based photodetector is suitable for hybridisation on a silicon platform and is compatible with 10 Gbit/s operation.