Experimental characterization of apodized wavelength modulation spectroscopy for accurate quantitative measurement

Abstract

The potential and drawbacks of the apodized 2f/1f wavelength modulation spectroscopy are theoretically studied and experimentally characterized. We apply a near-infrared DFB-based laser spectrometer, tunable around the R(32) CO2 absorption line centered at 6369.408 cm−1. The performance of the apodized method is shown by minimizing the pressure deviation between the gauge and experimental pressures by using the beneficial effect of the scaling (Formula presented.) -factor. This factor equalizes the experimental and simulated peak heights of the CO2 absorption trace. We found that when (Formula presented.) -factor is varied up to its optimum value of ~200, a pressure deviation of nearly zero is obtained at a case pressure of 19 ± 0.5 mbar. Under such optimum condition a minimum uncertainty of ±1 mbar is also obtained for the pressure deviation. However, we further acquired that far from this optimum condition, compared to the common method, the apodized approach is also capable of reducing the pressure deviation by ~13.5 % at 20 ± 0.5 mbar of CO2 pressure, indicating the performance of the proposed method for precise pressure measurement of a gas sample, regardless of the optical limits. © 2016, Springer Science+Business Media New York.