Simulation and Measurement of AlScN-Based Photonic Devices*

Scalable production of nonlinear photonic devices would greatly benefit from new CMOS-compatible materials with strong optical nonlinearities. AlScN is one option as higher Sc concentration enhances its second-order optical nonlinearity. However, while it has been used in piezoelectric devices, AlScN has not been utilized in nonlinear photonic devices. Here, we design and measure passive AlScN-based photonic devices as a step towards AlScN-based modulators. The material platform is amorphous silicon (α-Si) on AlScN on sapphire; we use AlScN with 20% Sc to balance enhanced nonlinearity and loss. By etching α-Si to define photonic structures, we can use well-established fabrication procedures. Based on simulations, a thin layer of etched α-Si provides sufficient index contrast to guide light and let it interact with AlScN. We designed grating couplers to efficiently couple the fundamental TM mode into the waveguide, which will allow us to use the largest nonlinear component, d₃₃, in AlScN. Measured waveguide devices have insertion losses around -30 dB, with propagation loss around -10 dB/cm after adding oxide cladding. We also demonstrate a Mach-Zehnder interferometer, which could be used as the passive component of an AlScN-based electro-optic modulator.