Mid-infrared methane detection in a photonic bandgap fiber using a broadband optical parametric oscillator

We demonstrate methane sensing using a photonic bandgap fiber-based gas cell and broadband idler pulses from a periodically-poled lithium niobate femtosecond optical parametric oscillator. The hollow core of the fiber was filled with a methane:nitrogen mixture, and Fourier transform spectroscopy was used to measure transmission spectra in the 3.15–3.35 µm methane absorption region. The method has applications in gas sensing for remote or hazardous environments and potentially at very low concentrations.