Etched Silicon-on-Insulator Microring Resonator for Ultrasound Measurement

Abstract

A novel integrated optical ultrasound sensor based on silicon-on-insulator (SOI) platform is proposed, theoretically analyzed and experimentally demonstrated. By using a selectively etched SOI microring resonator in an add-drop structure, the technique provides a linear and distortion-free sensing response to the ultrasound signal as it prevents the coupling region deformation and removes variations from the power fluctuation of the optical source. The proof-of-concept experimental demonstration of the proposed sensor shows the detection of air-coupled ultrasound pressure at different frequencies and magnitudes, a frequency sensing resolution of 30 Hz and a wide acceptance angle around 75 degrees.

Acoustic Sensing Performance Investigation Based on Grooves Etched in the Ring Resonators

“…In the frequency response experiment, the output amplitude of the SG is kept at 10 V to maintain the stability of the sound pressure level. Song et al calibrated the performance of the polymer ring resonator [ 26 ] at 40 kHz, and the SOI microring resonator produced by Yang et al’s [ 27 ] response frequency points are tested at 40 kHz, 58 kHz, 200 kHz, and 300 kHz to indicate the frequency range. On this basis, we lessen the frequency interval.…”

“…SNR is the difference between the peak and noise floor. Yang et al proposed the SOI microring resonator [ 27 ] which has an SNR of over 50 dB at the measured frequency of 58 kHz. In the paper, we measured frequency at 1 kHz with SNR over 54 dB and calculated MDP further.…”

“…However, the performance demonstrated in the experiment is only at 40 kHz and the sensitivity is expressed by the signal-to-noise ratio (SNR) of just 2.86 dB/Pa. Moreover, in 2020, the etched SOI microring resonator for ultrasound measurement was designed by the University of Sydney [ 27 ], depicting a selectively etched microring resonator in an add-drop structure. It provides a linear and distortion-free sensing response to the ultrasound signal.…”

Optical ultrasound sensors for photoacoustic imaging: a narrative review

“…Resonance-based optical ultrasound sensors including Fabry-Perot (FP) sensors (44)(45)(46)(47), microring resonators (36), Bragg grating sensors (48)(49)(50) and sensors based on surface plasmon resonance (SPR). The emergence of resonancebased sensors benefits from technical advances in fiber optics and silicon photonic integration such as silicon-oninsulators (47,49,51,52).…”

“…Microring resonators are commonly fabricated in silicon-based (51,81,82) or polymer platforms (36,79).…”