Analysis of second-order radial mode dips in racetrack optical ring resonator based on SOI rib waveguide

In this paper, detailed design and analysis of a polarization mode splitting resonator based on silicon-on-insulator rib waveguide is presented. By analyzing the mode birefringence in the ultra-small rib waveguide, the directional coupler is introduced to the micro-ring resonator to realize the splitting of the quasi-TE and quasi-TM polarization modes from the same output port in specific wavelength range. It is demonstrated that after splitting the quasi-TM polarization mode, the Q value of the quasi-TE polarization mode is 23000±1000, about twice of that without splitting the quasi-TM polarization mode. This novel characteristic of race-track ring resonators is quite promising in many applications of optical components, such as the electro-optical modulators.