Harbin Institute of Technology, Harbin, China
Received Date: November 03, 2016; Accepted Date: November 04, 2016; Published Date: November 11, 2016
Citation: Ma Y (2016) The New Development of QEPAS Trace Gas Sensor. J Laser Opt Photonics 3:e111. doi: 10.4172/2469-410X.1000e111
Copyright: © 2016 Ma Y. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a novel technique for trace gas sensing which was invented by Prof. Tittel’s group in 2002 . QEPAS uses a quartz tuning fork (QTF) as acoustic wave transducer. It process merits of high selectivity, high sensitivity and immune to environmental noise . Therefore it was widely used in many fields and different sensor architecture was developed.
■ Multi-QEPAS (M-QEPAS) sensor: Instead of one QTF employed in QEPAS sensor, multi QTFs was used to build M-QEPAS. The M-QEPAS signal amplitude was enhanced by addition of signal level of each QTF . The schematic plot of M-QEPAS using two QTFs was shown in Figure 1.
■ All-fiber QEPAS sensor: Compared with mirrors, fiber has more stable and flexible configuration. Therefore, the all-fiber structure would save many optical devices, and the whole system of the QEPSA will be more stable and cheaper. An all-fiber QEPAS sensor was demonstrated in . A fiber beam splitter and three QTFs were employed to perform multi-point detection and demonstrated the potential of spatially resolved measurements (Figure 2).
■ Planar laser based QEPAS sensor: The laser beam was shaped as a planar line laser between the gap of the QTF prongs when a cylindrical lens was used . Compared with spherical lens, the planar laser based QEPAS sensor has the advantageous of easier laser beam alignment and a reduction of stringent stability requirements (Figure 3).