2-D Far Field Beam Steering Using Electro-Optics and Acousto-Optics in Sputtered Sc Doped AlN

<p dir="ltr">The increasing demand for advanced solid-state LiDAR systems has accelerated research into photonic integrated circuit (PIC) based optical phased arrays (OPAs). OPAs offer compact, electrically controlled beam steering, but their performance is fundamentally limited to one dimension unless complemented by additional mechanisms for out-of-plane control. Two-dimensional beam steering is essential for high-resolution LiDAR and free-space communication, motivating the exploration of acousto-optic (AO) steering to provide broadband, electrically tunable emission beyond the in-plane control of OPAs. While lithium niobate has enabled demonstrations of electro-optic and acousto-optic devices, its incompatibility with silicon processing poses challenges for large-scale integration. Scandium-doped aluminum nitride (ScAlN), a material known for strong piezoelectricity and CMOS-compatible film growth, emerges as a promising alternative photonic platform for two-dimensional beam steering. </p><p dir="ltr">In this thesis, we present the first systematic study of Sc0.30Al0.70N photonic devices spanning waveguides, electro-optic modulators, surface acoustic wave (SAW) devices, and beam steering systems. We demonstrate low-loss waveguides with propagation losses as low as 1.6 dB/cm and racetrack resonators with loaded quality factors exceeding 87,000. We fabricate and characterize electro-optic modulators, extracting r13 values up to 0.194 pm/V. We design and test 2.4 GHz interdigitated transducers with electromechanical coupling k 2 t of 0.35% and resonator quality factors above 250, establishing the feasibility of integrating SAW devices with photonics on ScAlN films. Building on these results, we demonstrate the first ScAlN-based optical phased array, achieving angular beam shifts up to −1.21◦ under applied bias, and integrate AO-compatible IDTs with functioning optical waveguides as a step toward acousto-optic beam steering. </p><p dir="ltr">Together, these results establish ScAlN as a viable silicon-compatible photonic platform and provide the first pathway toward two-dimensional beam steering using both electro-optic and acousto-optic effects, paving the way for scalable solid-state LiDAR systems.</p>