Rapid Multipoint Gas Sensing Using a Silicon-Photonic-Integrated Widely-Tunable Narrow-Linewidth Laser by FMCW Interferometry

We present a spectroscopic method using a silicon-photonic-integrated laser by frequency-modulated continuous-wave (FMCW) interferometry to realize rapid multipoint gas sensing. The employed hybrid integrated external cavity laser has a wide tuning range of 147 GHz, a narrow linewidth of 180 kHz and a high sweeping speed of 294 THz/s (∼2700 nm/s), enabling sub-millisecond multipoint spectroscopic gas sensing. In the proof-of-concept experimental demonstration, three methane sensing nodes are deployed along a 30-m optical fiber, achieving a measurement sensitivity of 6 ppm with a time resolution of 0.5 ms and a positioning spatial resolution of 0.7 mm. Having the advantage of high spatiotemporal resolution, our proposed method promotes a novel way of developing spectroscopic gas sensors for challenging safety monitoring applications where spatially resolved chemical analysis with fast response is required.