Very long optical path-length from a compact multi-pass cell

TL;DR

This paper presents a compact multi-pass optical cell design that achieves an exceptionally long optical path-length of over 50 meters, enhancing laser absorption spectroscopy applications.

Contribution

It introduces a novel cylindrical mirror configuration that significantly extends optical path-lengths in a compact, robust design for trace-gas detection.

Findings

Achieved a 50.31 m optical path-length with 40 mm diameter mirrors.

Demonstrated mechanical stability suitable for practical use.

Provided conditions for maintaining very long path-lengths.

Abstract

The multiple-pass optical cell is an important tool for laser absorption spectroscopy and its many applications. For most practical applications, such as trace-gas detection, a compact and robust design is essential. Here we report an investigation into a multi-pass cell design based on a pair of cylindrical mirrors, with a particular focus on achieving very long optical paths. We demonstrate a path-length of 50.31 m in a cell with 40 mm diameter mirrors spaced 88.9 mm apart - a 3-fold increase over the previously reported longest path-length obtained with this type of cell configuration. We characterize the mechanical stability of the cell and describe the practical conditions necessary to achieve very long path-lengths.