Two-Stage Taper Enhanced Ultra-High $Q$ As $_{2}$S $_{3}$ Ring Resonator on LiNbO$_{3}$

摘要

A hybrid optics platform consisting of $hbox{LiNbO}_{3}$ waveguides vertically coupled to high-index-contrast $hbox{As}_{2} hbox{S} _{3}$ waveguides can provide tight bend radii for ring resonators and strong tuning capability via electrical-optic effects in $hbox{LiNbO}_{3}$ substrate. A vertically integrated $hbox{As}_{2} hbox{S} _{3}$ ring resonator having an ultranarrow free spectral range (FSR) of 0.0579 nm and side-coupled to a low-index Ti-diffused:$hbox{LiNbO}_{3}$ 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- $muhbox{m}$ radius, which corresponds to a calculated intrinsic quality factor-${Q}$ as high as $3.5times 10 ^{5}$. To our knowledge, this is the highest ${Q}$ factor reported for chalcogenide ring resonator planar waveguide devices.