Tilted Waveguide Gratings and Implications for Optical Waveguide-Ring Resonator

In this paper, a novel optical waveguide-type ring resonator by inserting titled waveguide gratings (TWGs) with the Brewster's angle is proposed. Using the Marcatili approximation, the electric fields for a rectangular waveguide is obtained. Then, the volume current method (VCM) is first developed for rectangular-core TWGs. By the VCM, the feasibility of the TWGs to filter the s-polarized light propagating in the resonator is proved. When a 4-cm-long 45°-titled TWG is applied to a silica waveguide-ring resonator, a polarization extinction ratio of 40 dB is obtained. The influences of the angular misalignment as well as the grating period of the TWGs are also evaluated.