Sub-parts-per-trillion level sensitivity in trace gas detection by cantilever-enhanced photo-acoustic spectroscopy

Abstract

An exceptional property of photo-acoustic spectroscopy is the zero-background in wavelength modulation configuration while the signal varies linearly as a function of absorbed laser power. Here, we make use of this property by combining a highly sensitive cantilever-enhanced photo-acoustic detector, a particularly stable high-power narrow-linewidth mid-infrared continuous-wave optical parametric oscillator, and a strong absorption cross-section of hydrogen fluoride to demonstrate the ability of cantilever-enhanced photo-acoustic spectroscopy to reach sub-parts-per-trillion level sensitivity in trace gas detection. The high stability of the experimental setup allows long averaging times. A noise equivalent concentration of 650 parts-per-quadrillion is reached in 32 minutes.

Purity Analysis of Gases Used in the Preparation of Reference Gas Standards Using a Versatile OPO-Based CRDS Spectrometer

“…. Reports in the literature on cw singly resonant OPO systems pumped at 1064 nm and operating at wavelengths below 2.5 µm are scarce [5,6]. is is due to the challenge to achieve stable operation as the PPLN gain bandwidth becomes very broad when the idler and signal are approaching the point of degeneracy (2128 nm).…”

“…is is due to the challenge to achieve stable operation as the PPLN gain bandwidth becomes very broad when the idler and signal are approaching the point of degeneracy (2128 nm). is wavelength range is of interest for various spectroscopic applications including the measurements of the quadrupole spectrum of molecular hydrogen [7], hydrogen uoride detection [6], and for the study of CO and CH 4 absorption lines, which are used in satellite retrieval measurements [8].…”

Narrow-Band Thermal Photonic Crystal Emitter for Mid-Infrared Applications

“…For sensing applications, the MIR domain is of a great interest, since the absorption peak due to photon-phonon coupling of the many simple molecules falls within this regime [1]. It has been shown that high performance though expensive and bulky spectroscopy can be reached with a sensitivity of down to part per trillion [2,3]. However, reaching such a performance in fully integrated system on chip device is far from trivial [4,5].…”

Quartz-Enhanced Photoacoustic Detection of Ethane in the Near-IR Exploiting a Highly Performant Spectrophone

“…Extreme working conditions combined with life-threatening risks, such as intoxication and poisoning of the operators, triggered many remote sensing solutions like the employment of unmanned aerial vehicle (UAVs) [8][9][10].Laser based spectroscopic techniques guarantee a high detection selectivity because of the narrow linewidths characterizing the laser source employed in the visible to the terahertz range, capable of exciting the target molecules while not being absorbed by the gas matrix [11][12][13][14]. The spectral purity of the excitation source, combined with wavelength/amplitude modulation approaches and the efficiency of the optical detection techniques result in reaching detection sensitivity levels as low as parts per quadrillion [15][16][17].Depending on the specific application, these unique characteristics can make laser-based sensors more suitable solutions for remote, fast, selective and sensitive trace gas detections relying on UAVs compared to electrochemical and semiconductor sensors. For instance, a non-dispersive infrared (NDIR) sensor was mounted on a UAV for environmental monitoring and proved to be able to detect CO 2 concentrations of 0.5% in air with a 10 s warm-up time [8].…”

“…Laser based spectroscopic techniques guarantee a high detection selectivity because of the narrow linewidths characterizing the laser source employed in the visible to the terahertz range, capable of exciting the target molecules while not being absorbed by the gas matrix [11][12][13][14]. The spectral purity of the excitation source, combined with wavelength/amplitude modulation approaches and the efficiency of the optical detection techniques result in reaching detection sensitivity levels as low as parts per quadrillion [15][16][17].…”