An acousto-Optic Modulator (AOM) formed by an Arsenic Trisulfide (As2S3) Mach-Zehnder interferometer (MZI), operating in a push-pull configuration and placed inside a surface acoustic wave (SAW) cavity on a Y-cut Lithium Niobate (LN) wafer is demonstrated. This is the first demonstration of such acousto-optic (AO) modulator in this As2S3 -LN hybrid platform. In this approach, the high index contrast of As2S3 waveguides is exploited to attain a high optical confinement. Additionally, the placement of the photonic MZI inside the SAW cavity enhances the AO interaction due to the high quality factor (Q) of the SAW resonator. An analytical expression that describes such enhancement as a function of the elasto-optic (EO) coefficient of As2S3 is derived in conjunction with COMSOL finite element methods to describe strain in the SAW cavity. By fitting this expression to experimental data, the EO coefficient (p11 and p12, where p11 \approx p12) for As2S3 is extracted to be 0.29 at the wavelength of 1550 nm. This is the first time that the EO coefficient of thin film As2S3 is experimentally derived.
See details here: https://ieeexplore.ieee.org/abstract/document/8935372