High-sensitivity acoustic sensing based on mechanical resonance modulation of whispering gallery mode optical resonator

The acoustic sensors for environmental noise monitoring and disaster warning have specific sensitivity and response frequency band requirements. We present a high-quality factor whispering gallery mode optical resonator combined with mechanical resonance modulation to enhance the detection of low-frequency acoustic signals. Although the resonator remains in a mechanical resonant state, low-frequency acoustic signals are loaded onto the high-frequency resonance, and this resonance overcomes the influence of low-frequency noise on the resonant spectrum shift. Experimental results show that the system exhibits excellent performance within the frequency range of 100 Hz to 1 kHz, achieving a sensitivity of 6.86 V/Pa at 500 Hz. Compared with the system without modulation, the signal-to-noise ratio of the sensing system under mechanical modulation improves by over 20 dB, and the minimum detectable pressure is 7.76 μPa/Hz1/2. These results confirm the system’s ability to detect weak low-frequency acoustic signals.