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

TL;DR

This paper presents a highly efficient, wideband acousto-optic modulator integrated into a silicon photonics foundry process, enabling scalable, low-cost production of advanced photonic devices with superior performance.

Contribution

The authors demonstrate the first high-efficiency, wideband AlScN-Si acousto-optic modulator compatible with commercial silicon photonics foundry processes.

Findings

Achieved -18.3 dB modulation efficiency over 112 MHz bandwidth.

Demonstrated an order of magnitude improvement in figure-of-merit over existing CMOS-compatible AOMs.

Enabled scalable, low-cost mass production of integrated acousto-optic devices.

Abstract

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 a highly efficient wideband acousto-optic modulator (AOM) implemented on a silicon photonics foundry process enabling high-yield low-cost mass production of AOMs with other photonic and electronic devices on the same substrate. In the reported structure, a 150 ${\mu}$m long AlScN-based acoustic transducer launches surface acoustic waves (SAW), which modulate the light passing through a silicon optical waveguide. A modulation efficiency of -18.3 dB over a bandwidth of 112 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 $BW(V_{\pi}L)^{-1}$ 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.