Abstract
This study describes development of non-intrusive measurement of CO_2 concentration by using coherent anti-Stokes Raman scattering (CARS) considering non-resonant background noise from channel wall. In order to suppress the influence of non-resonant background noise on measured values, beam diameter conversion was employed for measurement of CO_2 concentration. The relationship between CO_2 concentration and CARS intensity generated from CO_2 was obtained. The effect of background noise suppression was investigated by comparing the ratio of CARS to non-resonant noise of beam whose diameter is 5 mm, 7 mm and 10 mm.
