Acousto-optic Frequency Shifting and Modulation on a Hybrid Thin-film Lithium Niobate-Chalcogenide Integrated Platform

We demonstrate an efficient integrated acousto-optic frequency shifting and modulation on a hybrid thin-film lithium niobate (TFLN)–chalcogenide glass (ChG) integrated platform. In this approach, the TFLN-ChG heterogeneous layer is used to confine both optical and acoustic waves. The high elasto-optic coefficient of ChG enhances Bragg scattering efficiency compared to pure lithium niobate. A focusing surface acoustic wave is excited by using a curved interdigital transducer, which forms a focusing dynamic Bragg grating to deflect and frequency-shift the slab-waveguided light. The device achieves an upper-sideband conversion efficiency of ∼7.7%/W at 0.88 GHz, along with a carrier suppression of 37 dB. Furthermore, amplitude modulation is demonstrated, in which the modulated optical signal accurately replicates a 1 MHz electrical square wave and achieves switching speeds below 100 ns. The high performance and compact integration make this device promising for applications in microwave photonics.