Surface acoustic wave photonic devices in silicon on insulator

TL;DR

This paper introduces silicon on insulator surface acoustic wave photonic devices operating up to 8 GHz, enabling on-chip microwave-photonics signal processing without complex fabrication steps.

Contribution

It demonstrates a novel method for generating and detecting surface acoustic waves in silicon on insulator, avoiding suspension or hybrid materials, and showcases practical microwave-photonics applications.

Findings

Surface acoustic waves up to 8 GHz are generated and detected in silicon on insulator.

Wavelength conversion and true time delays up to 40 ns are achieved on-chip.

Microwave-photonic filters with six taps and 20 MHz bandwidth are demonstrated.

Abstract

Opto-mechanical interactions in planar photonic integrated circuits draw great interest in basic research and applications. However, opto-mechanics is practically absent in the most technologically significant photonics platform: silicon on insulator. Previous demonstrations required the under-etching and suspension of silicon structures. Here we present surface acoustic wave-photonic devices in silicon on insulator, up to 8 GHz frequency. Surface waves are launched through absorption of modulated pump light in metallic gratings and thermoelastic expansion. The surface waves are detected through photo-elastic modulation of an optical probe in standard race-track resonators. Devices do not involve piezo-electric actuation, suspension of waveguides or hybrid material integration. Wavelength conversion of incident microwave signals and acoustic true time delays up to 40 ns are demonstrated on-chip. Lastly, discrete-time microwave-photonic filters with up to six taps and 20 MHz wide passbands are realized using acoustic delays. The concept is suitable for integrated microwave-photonics signal processing