Wideband, Efficient AlScN-Si Acousto-Optic Modulator Integrated on a Commercially Available Silicon Photonics Process

Acousto-optic integration offers numerous applications, including low-loss microwave signal processing, nonreciprocal light propagation, frequency comb generation, and broadband acousto-optic modulation. State-of-the-art acousto-optic systems are mainly implemented entirely using in-house fabrication processes, which, despite excellent performance, typically suffer from low yield and are not compatible with mass production through foundry processes. Here, we demonstrate various AlScN-based acousto-optic modulators (AOM) integrated on a silicon photonics foundry process, enabling the high-yield, low-cost mass production of AOMs with other photonic and electronic devices on the same substrate. The surface acoustic wave transducers implemented with different aperture lengths and numbers of finger pairs exhibit efficient broadband modulation and explore the effect of different design parameters on AOM efficiency. A modulation efficiency of −14.6 dB over a bandwidth of 94 MHz is achieved, which, to our knowledge, is the highest reported efficiency and bandwidth combination among silicon-based AOMs, resulting in about an order of magnitude BW(VπL)−1 figure-of-merit improvement compared to the state-of-the-art CMOS-compatible AOMs. The monolithically integrated acousto-optic platform developed in this work will pave the way for low-cost, miniature microwave filters, true time delays, frequency combs, and other signal processors with the advanced functionality offered by foundry-integrated photonic circuits.