A femtosecond optical parametric oscillator (OPO) has been used to characterize the transmission of a number of different all-silica photonic bandgap (PBG) fibers specifically developed for gas sensing in the mid-infrared region. One of these fibers was chosen for its optimum transmission band (bandgap) overlap with methane fundamental absorption spectrum around 3.2 μm. Fourier transform–infrared (FT-IR) spectroscopy of methane has been demonstrated using the air-core of the PBG fiber as a gas cell and the OPO as a light source for concentrations down to 1000 ppm. A comparison with theoretical predicted values is presented alongside the measurements. An evaluation of the signal noise suggests that a measurement resolution better than 100 ppm concentration is achievable using this system.
ASJC Scopus subject areas
- Analytical Chemistry
- Atomic and Molecular Physics, and Optics