All-Optical Detection of Acoustic Pressure Waves with applications in Photo-Acoustic Spectroscopy

TL;DR

This paper presents an all-optical acoustic pressure wave detection method using a bare single-mode fiber, enabling high-temperature and hazardous environment measurements with improved safety and robustness.

Contribution

The study introduces a novel fiber-based optical detection system for acoustic waves, eliminating the need for microphones and enhancing environmental resilience.

Findings

Detection sensitivity of approximately 50 ppm for NO₂

Effective operation above 200°C environments

Demonstrated detection of photo-acoustic generated sound waves

Abstract

An all-optical detection method for the detection of acoustic pressure waves is demonstrated. The detection system is based on a stripped (bare) single-mode fiber. The fiber vibrates as a standard cantilever and the optical output from the fiber is imaged to a displacement-sensitive optical detector. The absence of a conventional microphone makes the demonstrated system less susceptible to the effects that a hazardous environment might have on the sensor. The sensor is also useful for measurements in high temperature (above $200^{\circ}$C) environments where conventional microphones will not operate. The proof-of-concept of the all-optical detection method is demonstrated by detecting sound waves generated by the photo-acoustic effect of NO$_2$ excited by a 455 nm LED, where a detection sensitivity of approximately 50 ppm was achieved.