Demonstration of an As2S3-on-LiNbO3 Grating Coupler and its Application of Measuring a Grating-based Filter

We demonstrate the design, fabrication, and measurement results for an As
₂
S
₃
grating coupler on a LiNbO
₃
substrate. The proposed coupler was fabricated by a single lithography step followed by a single reactive ion etching step, which substantially reduces the processing steps compared to previously reported coupling between vertically integrated As
₂
S
₃
and LiNbO
₃
waveguides. The measured grating coupling loss is 3.75 dB at 1563 nm for TE polarization. In addition, a sidewall Bragg grating cavity was fabricated using the grating input and output couplers. The Bragg grating response had a full width at half maximum (FWHM) of 0.0375 nm around the resonance wavelength and a cavity free spectral range (FSR) of 0.36 nm. Applications of these vertically integrated As
₂
S
₃
grating couplers include 2-D beam steering using the electro-optic tuning afforded by the LiNbO
₃
substrate and electro-optic sensing.