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Sensors 2017, 17(12), 2792;

Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing

Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China
College of Engineering, Shantou University, 243 Daxue Road, Shantou 515063, China
Author to whom correspondence should be addressed.
Received: 3 November 2017 / Revised: 26 November 2017 / Accepted: 27 November 2017 / Published: 2 December 2017
(This article belongs to the Section Physical Sensors)
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A Pound-Drever-Hall (PDH)-based mode-locked cavity-enhanced sensor system was developed using a distributed feedback diode laser centered at 1.53 µm as the laser source. Laser temperature scanning, bias control of the piezoelectric ceramic transducer (PZT) and proportional-integral-derivative (PID) feedback control of diode laser current were used to repetitively lock the laser modes to the cavity modes. A gas absorption spectrum was obtained by using a series of absorption data from the discrete mode-locked points. The 15 cm-long Fabry-Perot cavity was sealed using an enclosure with an inlet and outlet for gas pumping and a PZT for cavity length tuning. The performance of the sensor system was evaluated by conducting water vapor measurements. A linear relationship was observed between the measured absorption signal amplitude and the H2O concentration. A minimum detectable absorption coefficient of 1.5 × 10–8 cm–1 was achieved with an averaging time of 700 s. This technique can also be used for the detection of other trace gas species by targeting the corresponding gas absorption line. View Full-Text
Keywords: infrared absorption spectroscopy; cavity enhanced absorption spectroscopy; gas sensor infrared absorption spectroscopy; cavity enhanced absorption spectroscopy; gas sensor

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He, Q.; Lou, M.; Zheng, C.; Ye, W.; Wang, Y.; Tittel, F.K. Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing. Sensors 2017, 17, 2792.

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