Ultra-high-enhancement-factor integrated long-wave infrared gas sensor based on the tapered sub-wavelength grating slot waveguide

In this paper, an on-chip long-wave infrared gas sensor using the tapered sub-wavelength grating slot waveguide is proposed, designed, and analyzed in detail. At an operating wavelength of 7.70 μm, the slow-light enhancement factor of the designed waveguide gas sensor can reach 6.1516 by introducing the slow-light effect and carefully optimizing structural parameters. When the methane is treated as the target gas, the sensitivity and limit of detection are 19.0341 and 0.18524 ppm, respectively. If nitrous oxide is regarded as the target gas, the corresponding sensitivity and limit of detection will be 159.2375 and 0.02173 ppm.