Optical Gyrator and Microwave-to-Optical Converter using HBAR modes

Integrated photonic devices based on Silicon Nitride (Si 3 N 4 ) waveguides enable nonlinear frequency conversion, exhibit low propagation loss, and have led to advances in optical sensing, ultrafast ranging, and coherent communication [1] , [2] . Due to the presence of inversion symmetry, and thus lack of χ 2 nonlinearity, it is challenging to electrically modulate the refractive index of Si 3 N 4 . Integration of Aluminum Nitride (AlN) piezoelectric actuator on Si 3 N 4 provides a platform for microwave frequency acousto-optic modulation by exciting high over-tone bulk acoustic wave resonant modes (HBAR) in the wafer, as demonstrated by [3] , [4] .