Browsing by Author "Vitiello, Miriam S."

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    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, Vincenzo
    We 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.
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    THz Quartz-enhanced photoacoustic sensor for H2S trace gas detection
    (The Optical Society, 2015) Spagnolo, Vincenzo; Patimisco, Pietro; Pennetta, Riccardo; Sampaolo, Angelo; Scamarcio, Gaetano; Vitiello, Miriam S.; Tittel, Frank K.
    We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H2S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H2S rotational absorption line with a line-strength as small as S = 1.13·10−22 cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient αmin = 2.3·10−7 cm−1 and a normalized noise-equivalent absorption NNEA = 4.4·10−10W·cm−1·Hz-1/2, several times lower than the values previously reported for near-IR and mid-IR H2S QEPAS sensors.