Measurements of CO_2 in a multipass cell and in a hollow-core photonic bandgap fiber at 2 μm

摘要

Recently, hollow-core photonic bandgap fibers (HC-PBFs) for use in the 2 μm wavelength region have become available. We have employed tunable diode laser absorption spectroscopy (TDLAS) to quantify CO_2 in nitrogen, injected into a HC-PBF. Our spectrometer contains both an HC-PBF-based absorption cell and an astigmatic Herriott multipass gas cell. The Herriott cell was used for comparison with the HC-PBF cell. The HC-PBF cell's sensitivity and limit of detection were calculated to be 3.5 × 10~(-4) cm~(-1)-Hz~(-1/2) and 59 ppm·m, respectively. To substantiate the spectrometer performance, a measurement was done in the Herriott cell probing a reference gas mixture with nominal 400 μmol/mol CO_2 in N_2. The spectromet-ric results were in good agreement with the reference value. The relative standard uncertainty of the spectrometric result was found to be at the ±2 % level.