Quartz-Enhanced Photoacoustic Spectroscopy: A Review

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

doi:10.3390/s140406165

Cited by 351 publications

(293 citation statements)

References 101 publications

(113 reference statements)

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“…The water absorption spectra are obtained by scanning the laser optical frequency, adding a voltage ramp to the laser current at a frequency of 20 mHz. The QTF electrical signal S can be expressed as [6,22]:…”

Section: Qepas Sensing With Custom-made Tuning Forksmentioning

confidence: 99%

“…This acoustic signal is then detected either by a microphone (conventional PAS) or by means of piezoelectric quartz tuning fork (QTF), both acting as acousto-electric transducers. This now well-established variant of PAS is known as quartz-enhanced photoacoustic spectroscopy (QEPAS) [6,7]. QEPAS operation requires proper focalization of the excitation laser beam between the prongs of the QTF and modulation of the excitation source at a frequency matching one of the resonant frequencies of the QTF.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy

Tittel¹,

Sampaolo²,

Patimisco³

et al. 2016

Opt. Express

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Abstract:A detailed investigation of a set of custom quartz tuning forks (QTFs), operating in the fundamental and first overtone flexural modes is reported. Support losses are the dominant energy dissipation processes when the QTFs vibrate at the first overtone mode. These losses can be decreased by increasing the ratio between the prong length and its thickness. The QTFs were implemented in a quartz enhanced photoacoustic spectroscopy (QEPAS) based sensor operating in the near-IR spectral range and water vapor was selected as the gas target. QTF flexural modes having the highest quality factor exhibit the largest QEPAS signal, demonstrating that, by optimizing the QTF prongs sizes, overtone modes can provide a higher QEPAS sensor performance with respect to using the fundamental mode.

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Section: Qepas Sensing With Custom-made Tuning Forksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy

Tittel¹,

Sampaolo²,

Patimisco³

et al. 2016

Opt. Express

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show abstract

“…6 A number of different light sources (QCLs, LEDs, DFBs, OPOs and more) have been reported used in QEPAS experiments. [15][16][17][18][19][20] OPOs seem to be the optimal choice for providing large wavelength tunability, high energy, molecular selectivity and cost-effective device for the generation of infrared light in the 1.5 to 5 µm spectral range. 21 Therefore, a pulsed single mode mid-infrared (MIR) OPO has been developed.…”

Section: Methodsmentioning

confidence: 99%

“…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. The stiffness of quartz provides an efficient means of confining the acoustic energy in the prongs of the QTF, resulting in large quality factors (Q-factors) of the order 100000 in vacuum and 3-8000 at atmospherical pressures.…”

Section: Introductionmentioning

confidence: 99%

Quartz-enhanced photo-acoustic spectroscopy for breath analyses

Petersen¹,

Lamard²,

Feng³

et al. 2017

SPIE Proceedings

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An innovative and novel quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for highly sensitive and selective breath gas analysis is introduced. The QEPAS sensor consists of two acoustically coupled microresonators (mR) with an off-axis 20 kHz quartz tuning fork (QTF). The complete acoustically coupled mR system is optimized based on finite element simulations and experimentally verified. Due to the very low fabrication costs the QEPAS sensor presents a clear breakthrough in the field of photoacoustic spectroscopy by introducing novel disposable gas chambers in order to avoid cleaning after each test. The QEPAS sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared optical parametric oscillator (MIR OPO). Spectroscopic measurements of methane and methanol in the 3.1 µm to 3.7 µm wavelength region is conducted. Demonstrating a resolution bandwidth of 1 cm −1 . An Allan deviation analysis shows that the detection limit at optimum integration time for the QEPAS sensor is 32 ppbv@190s for methane and that the background noise is solely due to the thermal noise of the QTF. Spectra of both individual molecules as well as mixtures of molecules were measured and analyzed. The molecules are representative of exhaled breath gasses that are bio-markers for medical diagnostics.

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“…2427 Limit of Detection (LOD) values of parts-per-trillion (ppt) have been demonstrated using quartz-enhanced photoacoustic spectroscopy (QEPAS) systems. 28,29 One of the main reasons for the success of photothermal techniques is the fact that the signal is only originating from the absorption whereas in conventional transmission spectroscopy methods, scattering and reection losses inuence the measured signal. 17 This makes these techniques particularly attractive for applications in the eld.…”

mentioning

confidence: 99%

On-Chip Mid-Infrared Photothermal Spectroscopy Using Suspended Silicon-on-Insulator Microring Resonators

et al. 2016

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Mid-infrared spectroscopic techniques rely on the specific ”fingerprint” absorption lines of molecules in the mid-infrared band to detect the presence and concentration of these molecules. Despite being very sensitive and selective, bulky and expensive equipment such as cooled mid-infrared detectors is required for conventional systems. In this paper, we demonstrate a miniature CMOS-compatible Silicon-on-Insulator (SOI) photothermal transducer for mid-infrared spectroscopy which can potentially be made in high volumes and at a low cost. The optical absorption of an analyte in the mid-infrared wavelength range (3.25–3.6 μm) is thermally transduced to an optical transmission change of a microring resonator through the thermo-optic effect in silicon. The photothermal signal is further enhanced by locally removing the silicon substrate beneath the transducer, hereby increasing the effective thermal isolation by a factor of 40. As a proof-of-concept, the absorption spectrum of a polymer that has been locally patterned in the annular region of the resonator was recovered using photothermal spectroscopy. The spectrum is in good agreement with a benchmark Fourier-transform infrared spectroscopy (FTIR) measurement. A normalized noise equivalent absorption coefficient (NNEA) of 7.6 × 10–6 cm–1 W/Hz1/2 is estimated.

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Quartz-Enhanced Photoacoustic Spectroscopy: A Review

Cited by 351 publications

References 101 publications

Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy

Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy

Quartz-enhanced photo-acoustic spectroscopy for breath analyses

On-Chip Mid-Infrared Photothermal Spectroscopy Using Suspended Silicon-on-Insulator Microring Resonators

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