Atmospheric Environment Monitoring by Antiresonant Fiber-Enhanced Raman Spectroscopy With Sub-ppm Sensitivity

Hollow-core antiresonant fibers (HC-ARFs), attributed to their lower loss, wide transmission bandwidth, and low silica signals, have found widespread utilization in fiber-enhanced Raman spectroscopy (FERS). The system’s detection capability can be effectively enhanced by increasing the effective length of HC-ARF. We investigated the silica signals of nodeless antiresonant fiber of different lengths in a transmission system, revealing that the generation of silica signals can be attributed to two parts: one component arises from the overlapping interaction between the laser’s transmission within the fiber core and the microstructure, whereas the other component results from the leakage of the laser into the cladding during transmission. The limit of detection (LOD) of the system based on a 5-m-long HC-ARF is 0.51 ppm for 12C16O2, 0.14 ppm for 13C16O2, 0.22 ppm for 12C16O18O, and 0.098 ppm for CH4, respectively, with an input laser power of 1.6 W and an integration time of 900 s. The system demonstrates its excellent detection and isotopic analysis capabilities.