Thermoelastic surface acoustic waves in low-loss silicon nitride integrated circuits

TL;DR

This paper demonstrates thermoelastic surface acoustic waves in low-loss silicon nitride circuits, enabling efficient acousto-optic modulation without additional materials, advancing integrated microwave and programmable photonics.

Contribution

It introduces thermoelastic SAWs in Si3N4 circuits for acousto-optic modulation, achieving significant phase modulation enhancement and spectral control without extra materials.

Findings

13.6 dB phase modulation enhancement with multi-pass configuration

8 dB suppression ratio in single-sideband intermodal scattering

Observation of intensity modulation in a ring resonator

Abstract

Acousto-optic modulation in photonic integrated circuits harness the applications that include signal processing, quantum photonics and microwave photonics. However, silicon nitride ($\rm{Si_3N_4}$), as a main-stream low-loss scalable photonic platform, suffers from the lack of piezoelectric effect and therefore the hybrid co-integration with other materials is always required for acousto-optic modulation. Here, we employed thermoelastic surface acoustic waves (SAW) in a 8 dB/m propagation loss $\rm{Si_3N_4}$ integrated circuits without adding extra materials. A phase modulation efficiency enhancement of 13.6 dB is realized with a multi-pass configuration. Furthermore, a single-sideband intermodal scattering with a suppression ratio of 8 dB is measured and an intensity modulation is observed by incorporating the phase modulation into a ring resonator spectral. This thermoelastic SAW technique, as an initial step of acousto-optic modulation in low-loss $\rm{Si_3N_4}$ platform, is promising for integrated microwave photonics and programmable photonics applications.