CO2 laser-based trace gas detection: a nonintrusive ammonia monitor with subsecond response time

摘要

Abstract: We describe a method to increase the tuning rate of a grating-tuned cw CO$-2$/ laser by using an intra-cavity ZnSe wedge as a tuning element. The wedge is mounted on a galvo element directly in front of the grating which forms one of the cavity mirrors. Its orientation determines the angle of incidence of the laser radiation on the grating, and can be adjusted thorugh the voltage applied to the galvo element. This allows fast, accurate switching between different laser lines at a switching rate of up to 30 Hz. This technique is useful for on-line background absorption correction in trace gas monitoring and for multicomponent analysis of gas samples. !11