Browsing by Author "Giglio, Marilena"
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Item Highly sensitive gas leak detector based on a quartz-enhanced photoacoustic SF6 sensor(The Optical Society, 2016) Sampaolo, Angelo; Patimisco, Pietro; Giglio, Marilena; Chieco, Leonardo; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, VincenzoThe implementation, performance validation, and testing of a gas-leak optical sensor based on mid-IR quartz-enhanced photoacoustic (QEPAS) spectroscopic technique is reported. A QEPAS sensor was integrated in a vacuum-sealed test station for mechatronic components. The laser source for the sensor is a quantum cascade laser emitting at 10.56 µm, resonant with a strong absorption band of sulfur hexafluoride (SF6), which was selected as a leak tracer. The minimum detectable concentration of the QEPAS sensor is 2.7 parts per billion with an integration time of 1 s, corresponding to a sensitivity of leak flows in the 10−9 mbar∙l/s range, comparable with state-of-the-art leak detection techniques.Item Improved Tuning Fork for Terahertz Quartz-Enhanced Photoacoustic Spectroscopy(MDPI AG, 2016) Sampaolo, Angelo; Patimisco, Pietro; Giglio, Marilena; Vitiello, Miriam S.; Beere, Harvey E.; Ritchie, David A.; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, VincenzoWe report on a quartz-enhanced photoacoustic (QEPAS) sensor for methanol (CH₃OH) detection employing a novel quartz tuning fork (QTF), specifically designed to enhance the QEPAS sensing performance in the terahertz (THz) spectral range. A discussion of the QTF properties in terms of resonance frequency, quality factor and acousto-electric transduction efficiency as a function of prong sizes and spacing between the QTF prongs is presented. The QTF was employed in a QEPAS sensor system using a 3.93 THz quantum cascade laser as the excitation source in resonance with a CH₃OH rotational absorption line located at 131.054 cm(-1). A minimum detection limit of 160 ppb in 30 s integration time, corresponding to a normalized noise equivalent absorption NNEA = 3.75 × 10(-11) cm(-1)W/Hz(½), was achieved, representing a nearly one-order-of-magnitude improvement with respect to previous reports.Item Low power consumption quartz-enhanced photoacoustic gas sensor employing a quantum cascade laser in pulsed operation(SPIE, 2017) Sampaolo, Angelo; Patimisco, Pietro; Gluszek, Aleksander; Hudzikowski, Arkadiusz; Giglio, Marilena; Zheng, Huadan; Tittel, Frank K.; Spagnolo, VincenzoWe report here an analysis of the performance of a quartz-enhanced photoacoustic (QEPAS) system operating in a pulsed mode by employing a quantum cascade laser (QCL). The QEPAS system is based on a quartz tuning fork (QTF) having fundamental resonance frequency of 4.2 kHz and a first overtone resonance of 25.4 KHz. Water vapor was used as a target gas by selecting its absorption line falling at 1296.5 cm-1 with a line strength of 1.69⋅10-22 cm/molecule. The QEPAS signal was investigated, while varying the QCL duty-cycle from continuous wave operation, down to 5%, which corresponds to a laser power consumption of 0.17 mW and a pulse-width of 4 μs.Item Low-loss and single-mode tapered hollow-core waveguides optically coupled with interband and quantum cascade lasers(SPIE, 2018) Giglio, Marilena; Patimisco, Pietro; Sampaolo, Angelo; Kriesel, Jason M.; Tittel, Frank K.; Spagnolo, VincenzoWe report single-mode midinfrared laser beam delivery through a 50-cm-long tapered hollow-core waveguide (HCW) having bore diameter linearly increasing from 200 to 260 μm. We performed theoretical calculations to identify the best HCW-laser coupling conditions in terms of optical losses and single-mode fiber output. To validate our modeling, we coupled the HCW with an interband cascade laser and four quantum cascade lasers with their emission wavelengths spanning 3.5 to 7.8 μm, using focusing lenses with different focal lengths. With the best coupling conditions, we achieved single-mode output in the investigated 3.5 to 7.8 μm spectral range, with minimum transmission losses of 1.27 dB at 6.2 μm.Item Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7–7.6 μm Spectral Range(MDPI, 2016) Patimisco, Pietro; Sampaolo, Angelo; Mihai, Laura; Giglio, Marilena; Kriesel, Jason; Sporea, Dan; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, VincenzoWe demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7–7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5–12 µm. We demonstrated Gaussian-like outputs throughout the 4.5–7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range.Item Nitrous oxide quartz-enhanced photoacoustic detection employing a broadband distributed-feedback quantum cascade laser array(AIP Publishing, 2018) Giglio, Marilena; Patimisco, Pietro; Sampaolo, Angelo; Zifarelli, Andrea; Blanchard, Romain; Pfluegl, Christian; Witinski, Mark F.; Vakhshoori, Daryoosh; Tittel, Frank K.; Spagnolo, VincenzoWe present a gas sensing system based on quartz-enhanced photoacoustic spectroscopy (QEPAS) employing a monolithic distributed-feedback quantum cascade laser (QCL) array operated in a pulsed mode as a light source. The array consists of 32 quantum cascade lasers emitting in a spectral range from 1190 cm−1 to 1340 cm−1. The optoacoustic detection module was composed of a custom quartz tuning fork with a prong spacing of 1 mm, coupled with two micro-resonator tubes to enhance the signal-to-noise ratio. The QEPAS sensor was validated by detecting the absorption of the P- and R-branches of nitrous oxide. The measurements were performed by switching the array QCLs in sequence while tuning their operating temperature to retrieve the fine structure of the two N2O branches. A sensor calibration was performed, demonstrating a linear responsivity for N2O:N2 concentrations from 1000 down to 200 parts-per-million. With a 10 s lock-in integration time, a detection sensitivity of less than 60 parts-per-billion was achieved permitting the monitoring of nitrous oxide at global atmospheric levels.Item Quartz-enhanced photoacoustic sensor for ethylene detection implementing optimized custom tuning fork-based spectrophone(Optical Society of America, 2019) Giglio, Marilena; Elefante, Arianna; Patimisco, Pietro; Sampaolo, Angelo; Sgobba, Fabrizio; Rossmadl, Hubert; Mackowiak, Verena; Wu, Hongpeng; Tittel, Frank K.; Dong, Lei; Spagnolo, VincenzoThe design and realization of two highly sensitive and easily interchangeable spectrophones based on custom quartz tuning forks, with a rectangular (S1) or T-shaped (S2) prongs geometry, is reported. The two spectrophones have been implemented in a QEPAS sensor for ethylene detection, employing a DFB-QCL emitting at 10.337 μm with an optical power of 74.2 mW. A comparison between their performances showed a signal-to-noise ratio 3.4 times higher when implementing the S2 spectrophone. For the S2-based sensor, a linear dependence of the QEPAS signal on ethylene concentration was demonstrated in the 5 ppm −100 ppm range. For a 10 s lock-in integration time, an ethylene minimum detection limit of 10 ppb was calculated.Item Single-tube on beam quartz-enhanced photoacoustic spectrophones exploiting a custom quartz tuning fork operating in the overtone mode(SPIE, 2017) Giglio, Marilena; Sampaolo, Angelo; Patimisco, Pietro; Zheng, Huadan; Wu, Hongpeng; Dong, Lei; Tittel, Frank K.; Spagnolo, VincenzoWe report here on the realization of a single-tube on-beam quartz-enhanced photoacoustic (QEPAS) spectroscopy sensor employing a custom-made quartz tuning fork (QTF) with a large prong spacing. The prongs of the QTF have been designed in order to provide a quality factor twice higher when the QTF operates in the first overtone flexural mode than in the fundamental mode. The influence of the microresonator tube on the main parameters characterizing the sensing performance of the QEPAS spectrophone, including the quality factor, the magnitude of the QEPAS signal and the associated background noise was investigated in detail.Item Tuning forks with optimized geometries for quartz-enhanced photoacoustic spectroscopy(Optical Society of America, 2019) Patimisco, Pietro; Sampaolo, Angelo; Giglio, Marilena; dello Russo, Stefano; Mackowiak, Verena; Rossmadl, Hubert; Cable, Alex; Tittel, Frank K.; Spagnolo, VincenzoWe report on the design, realization, and performance of novel quartz tuning forks (QTFs) optimized for quartz-enhanced photoacoustic spectroscopy (QEPAS). Starting from a QTF geometry designed to provide a fundamental flexural in-plane vibrational mode resonance frequency of ~16 kHz, with a quality factor of 15,000 at atmospheric pressure, two novel geometries have been realized: a QTF with T-shaped prongs and a QTF with prongs having rectangular grooves carved on both surface sides. The QTF with grooves showed the lowest electrical resistance, while the T-shaped prongs QTF provided the best photoacoustic response in terms of signal-to-noise ratio (SNR). When acoustically coupled with a pair of micro-resonator tubes, the T-shaped QTF provides a SNR enhancement of a factor of 60 with respect to the bare QTF, which represents a record value for mid-infrared QEPAS sensing.