An all-Optical Photoacoustic Sensor for the Detection of Trace Gas

Abstract

A highly sensitive Fabry–Perot based transduction method is proposed as an all-optical alternative for the detection of trace gas by the photoacoustic spectroscopy technique. A lumped element model is firstly devised to help design the whole system and is successfully compared to finite element method simulations. The fabricated Fabry–Perot microphone consists in a hinged cantilever based diaphragm, processed by laser cutting, and directly assembled at the tip of an optical fiber. We find a high acoustic sensitivity of 630 mV/Pa and a state-of-the-art noise equivalent pressure, as low as at resonance. For photoacoustic trace gas detection, the Fabry–Perot microphone is further embedded in a cylindrical multipass cell and shows an ultimate detection limit of 15 ppb of NO in nitrogen. The proposed optical trace gas sensor offers the advantages of high sensitivity and easy assembling, as well as the possibility of remote detection.

Cantilever-enhanced photoacoustic spectroscopy for gas sensing: A comparison of different displacement detection methods

“…Michelson interferometer has high sensitivity and good stability, but the bulky volume and high cost limit its application in some specific fields. CEPAS based on Fabry-Perot interferometer is relatively compact [50] , [51] , [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] , [60] , [61] , [62] . A Fabry-Perot cavity is formed between the end facet of the fiber and the free end of the cantilever.…”

Optical Fiber Probe Microcantilever Sensor Based on Fabry–Perot Interferometer

“…The all-optical FP acoustic sensor with a cantilever structure has the merits of simple structure, compact size, and high stability of optical path compared to traditional mechanical cantilever photoacoustic spectroscopy systems. Thomas et al [ 86 ] designed and fabricated a hinged microcantilever-based microphone for trace NO detection in a nitrogen atmosphere. The stainless-steel hinged microcantilever is manufactured by laser cutting, as shown in Figure 10 .…”

Small-volume highly-sensitive all-optical gas sensor using non-resonant photoacoustic spectroscopy with dual silicon cantilever optical microphones

“…Though gas chromatography-mass spectrometry has high sensitivity to detect volatile and semi-volatile organic compounds, its columns need to be maintained regularly and are always with time consumption [8] . The optical gas sensing technology, such as tunable diode laser absorption spectroscopy (TDLAS) [9] , [10] and photoacoustic spectroscopy (PAS) [11] , [12] , [13] , has been widely applied because of their fast response, high sensitivity and selectivity. The gas detection based on TDLAS is achieved by detecting the attenuation of optical power, and the detection sensitivity is proportional to the gas absorption optical length.…”