Multipass laser cavity for efficient transverse illumination of an elongated volume

TL;DR

This paper introduces a robust multipass laser cavity design that efficiently illuminates large, elongated volumes transversely with minimal alignment issues, suitable for beam experiments and large-volume applications.

Contribution

The paper presents a novel multipass laser cavity scheme that provides large-volume transverse illumination with high robustness and no active stabilization.

Findings

Achieved illumination of a 7 x 25 x 176 mm^3 volume with 6 μm laser light.

Cavity design is highly tolerant to misalignment.

Experimental intensity distribution matches simulations.

Abstract

A multipass laser cavity is presented which can be used to illuminate an elongated volume from a transverse direction. The illuminated volume can also have a very large transverse cross section. Convenient access to the illuminated volume is granted. The multipass cavity is very robust against misalignment, and no active stabilization is needed. The scheme is suitable for example in beam experiments, where the beam path must not be blocked by a laser mirror, or if the illuminated volume must be very large. This cavity was used for the muonic-hydrogen experiment in which 6 $\mu$m laser light illuminated a volume of 7 x 25 x 176 mm^3, using mirrors that are only 12 mm in height. We present our measurement of the intensity distribution inside the multipass cavity and show that this is in good agreement with our simulation.