Design method of variable optical path length multi-pass cell

Abstract

According to the basic principle of the Herriott-type multi-pass cell (MPC), this paper analyzes the relationship between the optical path length (OPL) and the distance of the mirrors, and proposes a design method of variable optical path length MPC, which makes it easier to implement variable optical path length MPC. In the design, the incident angle is controlled to arrange the spots in a circle on the concave mirrors, and a method of adjusting the distance between the reflectors and the position of the exit point is proposed to realize the continuous and controllable numbers of passes (integer). MPC is frequently used to improve the sensitivity of gas detection, and the variable OPL designation is helpful for gas detecting of wide concentration range and the exploration of noise compensation methods in MPC.