Hybrid Thin-Film Lithium Niobate Micro-Ring Acousto-Optic Modulator with Low Half-Wave-Voltage-Length Product

Abstract

Highly efficient acousto-optic modulation plays a vital role in microwave-to-optical conversion. Herein, a hybrid thin-film lithium niobate (TFLN) racetrack micro-ring acousto-optic modulator (AOM) implemented with a low-loss chalcogenide (ChG) waveguide is demonstrated. By engineering the electrode configuration of the interdigital transducer, the double-arm micro-ring acousto-optic modulation is experimentally confirmed in a non-suspended ChG-loaded TFLN waveguide platform. Varying the position of the blue-detuned bias point, the half-wave-voltage-length product V _πL of the hybrid TFLN micro-ring AOM is as small as 9 mV cm. Accordingly, the acousto-optic coupling strength is estimated to be 0.48 Hz s^1/2 at an acoustic frequency of 0.84 GHz. By analyzing the generation of sideband photon number coupled out of the cavity, the ratio between the microwave photons and first-order optical sideband photons is calculated to be 2.2 × 10⁻⁷% at room temperature. Highly efficient micro-ring acousto-optic modulation thus provides new opportunities for expanding TFLN-ChG hybrid piezo-optomechanical devices applied in the low-power-consumption quantum information transduction.