Fabry-P\'{e}rot etalon walk-off loss in ring cavities

TL;DR

This paper analyzes the walk-off loss caused by Fabry-Pérot etalons in ring laser cavities, providing theoretical insights, numerical calculations, and experimental validation to optimize laser design.

Contribution

It offers a comprehensive analysis of walk-off loss in ring cavities with Fabry-Pérot etalons, including theory, numerical modeling, and experimental validation.

Findings

Loss can be minimized by realignment or matching reflectivity with refractive index

Numerical calculations extend beyond analytic limits

Tilt-tuning experiment demonstrates practical loss reduction

Abstract

Fabry-P\'erot etalons are widely used for laser frequency control. Inserting them in laser cavities imparts unavoidable walk-off loss and reduces the output power. Here, we treat the technology-relevant case of the walk-off loss of an etalon in a unidirectional ring cavity, which is a standard design of single-frequency lasers. We provide the theory background by discussing the analytic limits. The loss can be efficiently minimized by realignment, or by proper matching of the etalon's surface reflectivity with its refractive index. We numerically calculate the loss in the region uncovered by the analytic limits. We discuss practical laser design considerations, and we perform a tilt-tuning experiment in a single-frequency, solid-state laser setup.