Broadband detection of methane and nitrous oxide using a distributed-feedback quantum cascade laser array and quartz-enhanced photoacoustic sensing

Giglio, Marilena; Zifarelli, Andrea; Sampaolo, Angelo; Menduni, Giansergio; Elefante, Arianna; Blanchard, Romain; Pflüegl, Christian; Witinski, Mark F.; Vakhshoori, D.; Wu, Hongpeng; Passaro, Vittorio M. N.; Patimisco, Pietro; Tittel, Frank K.; Dong, Lei; Spagnolo, Vincenzo

doi:10.1016/j.pacs.2019.100159

Cited by 56 publications

(32 citation statements)

References 22 publications

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“…While the resulting increased spectral overlaps may potentially be dealt with using advanced data processing algorithms [ 44 ], it renders QEPAS sensors less suitable for providing broadband continuous spectra compared to other PAS methods. Instead, a viable approach could be to acquire PA signals at distinct, carefully considered, discrete wavelength points [ 45 ]. Another approach might be to design a system with a lower mechanical quality factor to allow for an increase in the applicable wavelength scan rate.…”

Section: Discussionmentioning

confidence: 99%

Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning

Christensen¹,

Høgstedt²,

Friis³

et al. 2020

Sensors

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Quartz-enhanced photoacoustic sensing is a promising method for low-concentration trace-gas monitoring due to the resonant signal enhancement provided by a high-Q quartz tuning fork. However, quartz-enhanced photoacoustic spectroscopy (QEPAS) is associated with a relatively slow acoustic decay, which results in a reduced spectral resolution and signal-to-noise ratio as the wavelength tuning rate is increased. In this work, we investigate the influence of wavelength scan rate on the spectral resolution and signal-to-noise ratio of QEPAS sensors. We demonstrate the acquisition of photoacoustic spectra from 3.1 μm to 3.6 μm using a tunable mid-infrared optical parametric oscillator. The spectra are attained using wavelength scan rates differing by more than two orders of magnitude (from 0.3 nm s−1 to 96 nm s−1). With this variation in scan rate, the spectral resolution is found to change from 2.5 cm−1 to 9 cm−1. The investigated gas samples are methane (in nitrogen) and a gas mixture consisting of methane, water, and ethanol. For the gas mixture, the reduced spectral resolution at fast scan rates significantly complicates the quantification of constituent gas concentrations.

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Section: Discussionmentioning

confidence: 99%

Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning

Christensen¹,

Høgstedt²,

Friis³

et al. 2020

Sensors

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“…In such a single-ended configuration, the resistor thermal noise directly affects the current signal generated by the QTF [13]. Transimpedance amplifiers have been widely employed for studying the performance of QEPAS sensors [14][15][16] and QTFs [17,18]. However, a different approach can also be used.…”

Section: Introductionmentioning

confidence: 99%

Front-End Amplifiers for Tuning Forks in Quartz Enhanced PhotoAcoustic Spectroscopy

et al. 2020

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A study of the front-end electronics for quartz tuning forks (QTFs) employed as optoacoustic transducers in quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing is reported. Voltage amplifier-based electronics is proposed as an alternative to the transimpedance amplifier commonly employed in QEPAS experiments. The possibility to use differential input/output configurations with respect to a single-ended configuration has also been investigated. Four different architectures have been realized and tested: a single-ended transimpedance amplifier, a differential output transimpedance amplifier, a differential input voltage amplifier and a fully differential voltage amplifier. All of these amplifiers were implemented in a QEPAS sensor operating in the mid-IR spectral range. Water vapor in ambient air has been selected as the target gas species for the amplifiers testing and validation. The signal-to-noise ratio (SNR) measured for the different configurations has been used to compare the performances of the proposed architectures. We demonstrated that the fully differential voltage amplifier allows for a nearly doubled SNR with respect to the typically used single-ended transimpedance amplifier.

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“…Extremely robust and reliable QEPAS sensors implementing standard QTF-based acoustic detection modules (ADM) were demonstrated in literature [23,24] and tested in real world applications [25], and also exploiting the single-mode beam delivery provided by optical fibers in the mid-IR [26,27]. Targeted applications were leak detection [28], hydrocarbon detection [29], and environmental monitoring [30,31].Starting from 2013, several studies have been performed to design QTFs with custom geometries optimized for QEPAS sensing [20,21,[32][33][34][35][36][37][38][39][40][41]]. An extensive investigation correlated the resonance frequency and the quality factor of the fundamental mode of the QTF with the prong sizes and geometry.…”

mentioning

confidence: 99%

“…It has been shown that if some additional mass is added to the free end of the prong, an increase of the global stress field is obtained, enhancing the stress distribution along the internal prong surface and the QTF sound-to-current transduction efficiency [32,33]. In addition, an enlargement of the prongs spacing of up to 1.5 mm can facilitate the optical alignment and minimize the photothermal noise level, allowing the use of laser beams characterized by a non-optimum spatial intensity distribution, such as high-power laser beams [34], THz quantum cascade lasers (QCLs) [35], arrays of QCLs [36,37] and dual-antinode configurations [38,39]. The advantages of low-frequency, high-quality factor QTFs with a large prong spacing have been demonstrated in the mid-infrared spectral range, where improvements in the detection limit have been obtained mainly due a the reduction of the photothermal noise contribution.…”

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confidence: 99%

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

et al. 2020

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In this paper the performances of two spectrophones for quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane gas sensing were tested and compared. Each spectrophone contains a quartz tuning fork (QTF) acoustically coupled with a pair of micro-resonator tubes and having a fundamental mode resonance frequency of 32.7 kHz (standard QTF) and 12.4 kHz (custom QTF), respectively. The spectrophones were implemented into a QEPAS acoustic detection module (ADM) together with a preamplifier having a gain bandwidth optimized for the respective QTF resonance frequency. Each ADM was tested for ethane QEPAS sensing, employing a custom pigtailed laser diode emitting at ~1684 nm as the exciting light source. By flowing 1% ethane at atmospheric pressure, a signal-to-noise ratio of 453.2 was measured by implementing the 12.4 kHz QTF-based ADM, ~3.3 times greater than the value obtained using a standard QTF. The minimum ethane concentration detectable using a 100 ms lock-in integration time achieving the 12.4 kHz custom QTF was 22 ppm.

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Broadband detection of methane and nitrous oxide using a distributed-feedback quantum cascade laser array and quartz-enhanced photoacoustic sensing

Cited by 56 publications

References 22 publications

Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning

Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning

Front-End Amplifiers for Tuning Forks in Quartz Enhanced PhotoAcoustic Spectroscopy

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

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