Abstract

We have fabricated a custom quartz tuning fork (QTF) with a reduced fundamental frequency, a larger gap between the prongs and the best quality factor in air at atmospheric conditions ever reported. Acoustic microresonators have been added to the QTF, these were optimized through experiments. We demonstrate a normalized noise equivalent absorption of 3.7 × 10−9 W·cm−1·Hz−1/2 for CO2 detection at atmospheric pressure. Influence of the inner diameter and length of the microresonators has been studied as well as the penetration depth between the QTF prongs.

Highlights

  • Detection of hazardous chemicals and greenhouse gases is one among the many challenges of our century

  • We demonstrate the performance of our detector and explain the influence of the dimensions of the acoustic resonators on the quality factor

  • Two longitudinal acoustic resonators are placed along the laser beam, inside the cavity, these are cut from stainless steel hypodermic needles

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Summary

Introduction

Detection of hazardous chemicals and greenhouse gases is one among the many challenges of our century. Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) appeared in 2002 [1] providing a good compromise between compacity and sensitivity. This technique involves the generation of a pressure wave through gas excitation with an amplitude, or wavelength, modulated laser and its detection with a Quartz Tuning Fork (QTF), usually complemented by longitudinal acoustic resonators. Commercial QTFs are well suited for vacuum use and present two major drawbacks for photoacoustic spectroscopy: a small gap between their prongs as well as a high resonance frequency. Standard QTFs present low quality factors at atmospheric pressure, and the small gap between the prongs makes it difficult for a laser beam to pass through. We demonstrate the performance of our detector and explain the influence of the dimensions of the acoustic resonators on the quality factor

Experimental Set Up
Results
Conclusions

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