Compact, spherical mirror-based dense astigmatic-like pattern multipass cell design aided by a genetic algorithm.

We propose a unique way to design multipass cells (MPCs), which combines cost-efficient spherical mirrors with the high-density pattern of astigmatic mirrors. Such functionality was accomplished using at least three standard spherical mirrors appropriately tilted, which breaks the parallelism between them. A genetic algorithm (GA) supported the cell configuration optimization. A 16 m and 23.8 m optical path length (OPL) MPC was developed, practically realized, and proved by a time-of-flight (TOF) experiment to demonstrate the principle. Finally, CO2 detection at 2004nm obtaining 0.4 ppmv limit of detection (LOD) using wavelength modulation spectroscopy (WMS) with 10 s averaging was performed.