Acoustic Sensing Characteristics Research Based On The Groove Structure Of Optical Waveguide Resonator

The acoustic detection technology based on optical technology is developing towards high sensitivity and wide band.Traditional acoustic sensors use moving parts such as vibrating diaphragm as sensing units,which are limited by the mechanical resonant frequency of moving parts,resulting in small detection sensitivity and narrow frequency response range.Optical microcavity has the advantages of high quality factor,strong anti-interference,easy miniaturization and integration,and is widely used in various fields.The acoustic sensing technology based on optical microcavity provides a new direction for the development of high sensitivity and wide band acoustic sensing technology.Ring resonator is a kind of basic optical structure unit manufactured by micro-nano machining technology.It has strong spatio-temporal enhancement effect and frequency selection effect.It is an effective way to improve the sensitivity of sound sensing and broaden the spectrum response range.An acoustic sensor based on evanescent field optical waveguide ring resonator is proposed in this paper.The acoustic sensor grooves the annular resonator and the grooves are used as direct sensitive structures to excite the evanescent field.A series of resonators with different groove sizes were fabricated for comparative analysis of acoustic performance.Acoustic parameters such as response bandwidth,sensitivity and signal-to-noise ratio varied with Q values caused by different grooves.This paper studies the following three aspects:(1)Analysis of sensing principleSound waves propagate forward in the air as longitudinal waves alternating between density and density.The density of the air medium will change with the compression and relaxation of the sound waves.This change is manifested as the offset of the resonant frequency on the macro level.Combined with the evanescent field theory and effective refractive index,the feasibility of detecting sound signal by evanescent field in ring resonator was preliminatively verified.(2)Ring resonator performance parameters and sensing testBased on the acoustic sensing effect of the optical waveguide ring resonator with evanescent field,ring resonators with different groove parameters were processed according to the simulation results,and the performance parameters FWHM,Q value,ER were tested,and an experimental system was built to test and compare the acoustic properties such as frequency response range,sensitivity,minimum detectable sound pressure,and finally the resolution and recording sensing were tested.(3)Influence of environmental parameters and cavity length variation on acoustic sensing performanceThe environmental parameters of ring resonator acoustic sensor are tested experimentally.The frequency response and sensitivity of the ring resonator acoustic sensor were tested by changing the ambient pressure,then the sensitivity was tested by changing the ambient temperature and humidity,and finally the sensing performance was tested by changing the length of the cavity.