Recent Progress in Infrared Absorption Spectroscopy for Gas Sensing With Discrete Optics, Hollow-Core Fibers and On-Chip Waveguides

Infrared absorption spectroscopy (IAS) is currently a powerful tool for gas sensing. Gas sensors based on IAS show advantages of high sensitivity, good selectivity and in-situ measurement. Typical infrared gas sensors include sensors based on discrete optics, hollow-core fiber sensors and on-chip sensors, suitable for different application environments. Discrete sensors and hollow-core fiber sensors have a relatively large volume and a heavy weight, but due to large light-gas interaction length (tens of meters or even kilometers), their sensitivity is obviously higher than on-chip gas sensors. Mature complementary metal oxide semiconductor (CMOS) fabrication process promotes the development of miniaturized on-chip sensors, which is portable in size, low in power consumption and light in weight. But the small on-chip sensor volume limits the interaction effect between light and gas analyte. Sensing techniques such as slow-light enhanced absorption spectroscopy and surface-enhanced infrared absorption spectroscopy are proposed to improve the on-chip sensing performance. In this paper, we review the gas sensing principle based on IAS briefly and the recent progress of the three kinds of sensors using different spectroscopy techniques. Finally, some conclusions and an outlook of IAS gas sensors are reached.