Extending the optical path of segmented circular multipass cells by reiteration of reflection patterns.

This Letter presents a novel, to the best of our knowledge, design element for the segmented circular multipass cell (SC-MPC) concept, which enables a substantial increase in optical path length without enlarging the cell footprint or sampling volume. It features a specific tilt of individual mirror segments within the cell to repeatedly redirect the laser beam propagation from one starlike pattern to another, thereby achieving multiple uses of mirror segments. We present the theoretical foundations, outline the pattern selection process, and characterize the resulting individually tilted segmented circular multipass cell (iSC-MPC) in a spectroscopic setting. The results demonstrate optical performance comparable to classical two-mirror long-path length absorption cells, but within a substantially smaller footprint. This compactness offers an inherent mechanical stability and robustness paired with high versatility, which makes the iSC-MPC highly potential for a wide range of applications.