Quartz-enhanced photoacoustic spectroscopy

Abstract

A new approach to detecting a weak photoacoustic signal in a gas medium is described. Instead of a gas-filled resonant acoustic cavity, the sound energy is accumulated in a high- Q crystal element. Feasibility experiments utilizing a quartz-watch tuning fork demonstrate a sensitivity of 1.2x10(-7) cm(-1) W/ radicalHz . Potential further developments and applications of this technique are discussed.

Compact QEPAS sensor for trace methane and ammonia detection in impure hydrogen

“…Quartz enhanced photoacoustic spectroscopy (QEPAS) is a rapidly developing, sensitive, selective spectroscopic technique for laser based trace gas detection with a fast response time [1,2]. QEPAS combines the main characteristics of photoacoustic spectroscopy (PAS) with the benefits of using a quartz tuning fork (QTF), thus providing an ultra-compact, cost-effective, robust acoustic detection module (ADM).…”

Quartz-enhanced photo-acoustic spectroscopy for breath analyses

“…Quartz tuning forks (QTFs) have shown great potential as sound transducers for PAS and have been increasingly applied to selective and sensitive detection of trace gases since its introduction in 2002. 11 Standard low cost QTFs with resonance frequencies at 32.7 kHz are typically used as sensors, however, also custom made QTFs have been reported. [12][13][14][15][16][17][18] The PA signal is proportional to the Q-factor: S ∝ QP α/f 0 , where P is the optical power, α is the molecular absorption coefficient and f 0 is the resonant frequency of the QTF.…”

Analog Front-End Circuitry in Piezoelectric and Microphone Detection of Photoacoustic Signals

“…There are many kinds of detectors used in photoacoustic equipment [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Some of them are quite sophisticated solutions-e.g., optical microphones [6,7], quartz resonator-based detectors [13][14][15], and microcantilevers for which the deflection is measured with interferometric techniques [16][17][18].…”

“…Some of them are quite sophisticated solutions-e.g., optical microphones [6,7], quartz resonator-based detectors [13][14][15], and microcantilevers for which the deflection is measured with interferometric techniques [16][17][18]. Such solutions are typically aimed at increases of the sensitivity of the detector, but usually they are associated with high complexity and cost.…”