A Gold Diaphragm-Based Fabry-Perot Interferometer With a Fiber-Optic Collimator for Acoustic Sensing

In this paper, a high sensitive fiber-optic Fabry-Perot interferometer sensor based on gold diaphragm for acoustic detection has been proposed and experimentally demonstrated. The extrinsic Fabry-Perot interferometer (EFPI) comprises a 140-nm-thick gold diaphragm and the end-face of a fiber-optic collimator, both of which are enclosed into a structure made of glass tubes. A fiber-optic collimator is first adopted in acoustic sensing to reduce the light loss and improve the sensitivity. The experimental results show that the proposed sensor has a wide flat response range from 400 Hz to 12 kHz, almost covering the primary frequency component of audible sound. The pressure sensitivity and the minimum detectable acoustic pressure level (MDP) are measured to be −175.7 dB re 1rad/ $\mu $ Pa@150Hz and $95.3~\mu $ Pa/Hz ^1/2 @2kHz, respectively. The proposed sensor has advantages of high sensitivity, wide flat response, low cost, and simple fabrication, which shows its potential as a fiber optical microphone with high sensitivity and high acoustic quality in practical applications.