Unified analysis of spatially-coupled absorption and saturation dynamics in multi-pass pumped thin-disk lasers

TL;DR

This paper introduces a comprehensive theoretical model for multi-pass pumped thin-disk lasers that unifies various physical effects, validated with experiments, and offers practical guidelines for optimizing high-power laser performance.

Contribution

It develops a unified self-consistent framework combining pump absorption, gain saturation, thermo-optic effects, and diffraction, with experimental validation for Yb:YAG thin-disk lasers.

Findings

Accurately predicts absorption, power, and beam quality within 3% error.

Proves the existence of a unique steady-state solution.

Provides guidelines for pump-power scaling and pass-number optimization.

Abstract

We present a theoretical framework that unifies pump absorption, gain saturation, thermo-optic distortion, and cavity diffraction into a self-consistent model of multi-pass pumped solid-state lasers. By deriving a theoretical formulation of the nonlinear coupling of the superimposed pump energy and effective absorption, we prove an unique steady-state solution exists. Applied to the multi-pass Yb:YAG thin-disk module, the framework is quantitatively validated with experiments, reproducing a well matched absorption tendency, errors in output power, beam diameter and M^2 within 3.0%, 1.7%, and 0.05 respectively. This approach provides predictive guidelines for pump-power scaling and pass-number optimization in high-power lasers.