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

Abstract

Acoustic detection based on optical technology has moved in the direction of high sensitivity and resolution. In this study, an optical waveguide acoustic sensor based on a ring resonator with the evanescent field is proposed. Grooves are introduced into the ring resonators as a direct sensitive structure to excite the evanescent field. A series of resonators with diverse grooves are fabricated for a comparative analysis of acoustic performance. The acoustic parameters of bandwidth, sensitivity, and signal-to-noise ratio (SNR) vary with different grooves indicated by the Q-factor. The results show that the ring resonators with variable-sized grooves exhibit excellent capability of acoustics detection. A maximum frequency of 160 kHz and a high sensitivity of 60.075 mV/Pa is achieved, with the minimum detectable sound pressure being 131.34 µPa/Hz1/2. Furthermore, the resonators with high Q-factors represent a remarkable sound resolution reaching 0.2 Hz. This work is of great significance for optimizing acoustic sensors and broadening the application range.

Ultrasensitive Acoustic Detection Using an Enlarged Fabry–Perot Cavity with a Graphene Diaphragm

“…According to FFT-processed spectra in Figure e, the F–P sensor with the EBC is capable of distinguishing mixed sound signals with a detection resolution of 0.01 Hz. Comparatively speaking, the 0.01 Hz detection resolution precedes the performance larger than 0.2 Hz in acoustic sensors previously published in literature studies. ,, …”

“…Comparatively speaking, the 0.01 Hz detection resolution precedes the performance larger than 0.2 Hz in acoustic sensors previously published in literature studies. 4,35,38 Given the merits presented before, the F−P acoustic sensor with the EBC has displayed potential speech detection capability. To prove the idea, a commercial microphone (B&K 4189) and the F−P sensor with the EBC simultaneously receive voice signals ("hello" in Chinese), as shown in Figure 5f−5h (man) and Figure 5i−5k (woman).…”

“…Besides the SNR, the minimum detectable sound pressure (MDP) also determines availability in a noisy environment and difficulty in signal processing. 34 In order to calculate the MDP, the relationship between the MDP and the SNR can be given by 35,36…”

“…Besides the SNR, the minimum detectable sound pressure (MDP) also determines availability in a noisy environment and difficulty in signal processing . In order to calculate the MDP, the relationship between the MDP and the SNR can be given by , MDP = p RBW · 10 SNR / 20 where RBW is the 3 dB resolution bandwidth of the amplitude-frequency spectrum at sound frequency. Referring to sound pressure shown in Figure S6a and eq , the MDP in the range of 0.5–18 kHz is calculated, as shown in Figure S6b.…”

Alternative Approach to Design and Optimization of High-Q Ring Resonators for Membrane-Free Acoustic Sensors

“…In the early stage, we developed an approach to the design and fabrication of a resonator, with a Q factor of up to 10 6 -10 7 , which was applied to a resonant micro-optic gyroscope and an optoelectronic oscillator [27,28]. Subsequently, optical waveguide membrane-free acoustic sensors based on grooves etched in ring resonators are proposed [29], and the resonators have Q-factors of up to 10 6 . The acoustic wave can be sensed by calculating the shift of the resonant frequency, due to the change in the air refractive index of the groove caused by the acoustic wave.…”