High sensitivity methane and ethane detection using low-loss mid-IR hollow-core photonic bandgap fibers

摘要

We present sub-ppm sensitivity, broadband gas absorption measurements using improved hollow-core photonic-bandgap fibers with low loss in the range 3-3.6 μm. The sensitivity levels, unprecedented for a fiber-based sensor system, were achieved by addressing the strong mid-IR vibrational bands through use of a high-intensity supercontinuum source and by exploiting long interaction lengths in the HC-PBGFs. We measured mixtures of methane (1034 ppm) and ethane (50.4 ppm) and attained 7 and 0.9 ppm sensitivities for 0.925 and 5.69 m long HC-PBGF samples, respectively, from high-resolution (0.2 nm) spectra. Significant scope for further sensitivity improvement exists through use of longer fibers in combination with more sophisticated sensing schemes.