Analysis of polarisation mode splitting characteristic in optical race-track resonator based on silicon-on-insulator rib waveguide

The detailed design and analysis of a polarisation mode splitting resonator based on a silicon-on-insulator rib waveguide are presented. By analysing the mode birefringence in the ultra-small rib waveguide, the directional coupler is introduced to the microring resonator to realise the splitting of the quasi-TE and quasi-TM polarisation modes from the same output port for a specific wavelength range. It is demonstrated that after splitting the quasi-TM polarisation mode, the Q-value of the quasi-TE polarisation mode is about 2.3 × 10⁴, almost twice of that without splitting the quasi-TM polarisation mode. This novel characteristic of a race-track resonator allows it to obtain single polarisation mode at a specific wavelength by itself. This characteristic makes a contribution to accurate wavelength selection, which has been proved to be very useful in the dynamic testing of electrooptical modulators and quite promising in many other applications of optical components.