TITLE:
Demonstration of an As2S3 Grating Coupler on Thin Film LiNbO3
AUTHORS:
Chen Zhang, Christi K. Madsen
KEYWORDS:
Thin Film Lithium Niobate, Arsenic Trisulfide Waveguide, Grating Coupler, Grating Cavity
JOURNAL NAME:
Optics and Photonics Journal,
Vol.8 No.4,
April
30,
2018
ABSTRACT: We present both design and experimental results for an As2S3 grating coupler on a thin film LiNbO3 substrate. A basic grating coupler structure is designed with coupling efficiency of 53% to a single mode fiber. A maximum simulated coupling efficiency of 78.8% is achieved, assuming a polymer bonding process. The basic structure was fabricated, and the coupling efficiency was measured to be at least 23.4% at 1540 nm. Some of the loss may be attributable to non-grating sources, such as waveguide tapers and testing fiber tails. A grating cavity was then measured using the grating couplers. The cavity waveguide propagation loss was 2.0 dB/cm. For a 400 nm thick As2S3 on 500 nm thin film LiNbO3 on insulator, the confinement factor in the LiNbO3 crystal is 82.3% when the As2S3 waveguide width is 400 nm, showing that As2S3-on-thin film LiNbO3 is an excellent candidate for thin film electro-optic applications.