High-Efficiency Acousto-Optic Modulation on Non-Suspended Thin-Film Lithium Tantalate

Acousto-optic (AO) interactions provide a powerful interface between the microwave and optical domains, enabling optical switching, non-reciprocal propagation, and efficient microwave-to-optical transduction. Here, we demonstrate high-efficiency AO modulation on a non-suspended lithium-tantalate-on-insulator (LTOI) platform. LTOI combines intrinsically low birefringence, a high optical-damage threshold, strong electro-optic and Kerr nonlinearities, and favorable acoustic properties. Our Mach-Zehnder interferometers achieve $V_{\pi }L=0.68$ $V\cdot cm$ , while racetrack resonators reach $V_{\pi }L=0.022$ $V\cdot cm$ , enabling microwave-to-optical conversion without suspended structures. Measurements across six in-plane propagation directions identify propagation along the crystal Z axis as the most efficient tested configuration, where the higher-order R1 mode produces the strongest MZI response. Temperature-dependent acoustic measurements and continuous RF-driven optical testing further demonstrate material-related operating stability. These results establish non-suspended LTOI as a robust platform for integrated acousto-optics with broad applications in communications, signal processing, and quantum information technologies.