Two-Stage Taper Enhanced Ultra-High Q As2S3 Ring Resonator on LiNbO3

A hybrid optics platform consisting of LiNbO3 waveguides vertically coupled to high-index-contrast As2S3 waveguides can provide tight bend radii for ring resonators and strong tuning capability via electrical-optic effects in LiNbO3 substrate. A vertically integrated As2S3 ring resonator having an ultranarrow free spectral range (FSR) of 0.0579 nm and side-coupled to a low-index Ti-diffused:LiNbO3 straight waveguide was designed and fabricated. Using improved design and fabrication processes, a low 1.2-dB/cm propagation loss in the ring with over 30 dB of extinction ratio was demonstrated on a fabricated 1.7-cm-long path ring resonator with a 400-mu m radius, which corresponds to a calculated intrinsic quality factor-Q as high as 3.5 x 10(5). To our knowledge, this is the highest Q factor reported for chalcogenide ring resonator planar waveguide devices.