Silicon photonic acoustic detector (SPADE) using a silicon nitride microring resonator

• DOI: 10.1016/j.pacs.2023.100527
• Publication Date: 2023-07-02T13:28:02Z
• Authors: Michael Nagli; Ron Moisseev; Nathan Suleymanov; Eitan Kaminski; Yoav Hazan; Gil Gelbert; Ilya Goykhman; Amir Rosenthal
• Keywords: Microring silicon-photonics acoustic detector; Optoacoustic imaging; MRR-SPADE; Physics; QC1-999; Silicon-photonics acoustic detector; Acoustics. Sound; QC221-246; SPADE; QC350-467; Photoacoustic imaging; Optics. Light; Research Article

Silicon photonics is an emerging platform for acoustic sensing, offering exceptional miniaturization and sensitivity. While efforts have focused on silicon-based resonators, silicon nitride resonators can potentially achieve higher Q-factors, further enhancing sensitivity. In this work, a 30 µm silicon nitride microring resonator was fabricated and coated with an elastomer to optimize acoustic sensitivity and signal fidelity. The resonator was characterized acoustically, and its capability for optoacoustic tomography was demonstrated. An acoustic bandwidth of 120 MHz and a noise-equivalent pressure of ∼ 7 mPa/Hz1/2 were demonstrated. The spatially dependent impulse response agreed with theoretical predictions, and spurious acoustic signals, such as reverberations and surface acoustic waves, had a marginal impact. High image fidelity optoacoustic tomography of a 20 µm knot was achieved, confirming the detector's imaging capabilities. The results show that silicon nitride offers low signal distortion and high-resolution optoacoustic imaging, proving its versatility for acoustic imaging applications.