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 π L 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.