Optical design of Lissajous pattern multipass cells with multiple spherical mirrors based on particle swarm optimization

We propose a method to intelligently design and optimize a multiple-spherical-mirrorbased multipass cell (MPC) with Lissajous patterns. The MPC consists of at least three spherical mirrors, which are placed in a rotationally symmetric arrangement. Particle swarm optimization (PSO) is performed to optimize the parameters of the MPC configurations and accelerate the design process. Two Lissajous patterned MPCs with three and five mirrors are built and tested experimentally. We further develop an open-path gas sensor based on a five-mirror-based MPC to detect methane concentrations in ambient laboratory air, and a detection precision of 1.1 ppb with a 123 s averaging time is realized. The PSO algorithm is efficient for optimizing the proposed MPC, which has superior proprieties of symmetry configuration, cost-effectiveness and high detection sensitivity and is well suited for trace gas sensing applications. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement