Post signal processing for CO gas spectroscopy using chip-based supercontinuum source

Abstract

Supercontinuum generation (SCG) is an attractive method to generate broadband optical sources in that it covers more than hundreds of nm bandwidths. In virtue of the advances in nanoscale designs of the nonlinear waveguides, their spectral coverages are allowed in ultraviolet (UV) to mid-infrared (MIR) regions and their bandwidths also extended more than 1 octaves. Since the ro-vibrational bands of the many sorts of gases reside in the infrared regions, there have been advances in absorption spectroscopies, which were demonstrated by transmitting SCG into gas cells [1] , [2]. To extract absorption data of specific gas molecules, it is essential to subtract background signals such as the envelope of the SCG and the effect of optical components, from the cell-transmitted signal. Extra measurement of N 2 cell transmission, linear fitting, and polynomial fitting have been implemented for it. Here, by applying an appropriate high-pass filter, we achieved a clear distinction of the absorption band of CO gas from the SCG transmitted through 400 Torr, 121 mm CO gas cell.