On thermal effects in solid state lasers: the case of ytterbium-doped materials

TL;DR

This paper reviews theoretical and experimental insights into thermal effects in solid-state lasers, especially focusing on ytterbium-doped materials, highlighting measurement techniques and clarifying misconceptions about thermal lensing.

Contribution

It provides a comprehensive overview of the theoretical basis and measurement tools for thermal effects in Yb-doped solid-state lasers, including new discussions on the thermo-optic coefficient.

Findings

Evaluation methods for temperature mapping in Yb-doped crystals

Clarification of the role of dn/dT in thermal lensing

Examples of thermal effects specific to Yb-doped materials

Abstract

A review of theoretical and experimental studies of thermal effects in solid-state lasers is presented, with a special focus on diode-pumped ytterbium-doped materials. A large part of this review provides however general information applicable to any kind of solid-state laser. Our aim here is not to make a list of the techniques that have been used to minimize thermal effects, but instead to give an overview of the theoretical aspects underneath, and give a state-of-the-art of the tools at the disposal of the laser scientist to measure thermal effects. After a presentation of some general properties of Yb-doped materials, we address the issue of evaluating the temperature map in Yb-doped laser crystals, both theoretically and experimentally. This is the first step before studying the complex problem of thermal lensing (part III). We will focus on some newly discussed aspects, like the definition of the thermo-optic coefficient: we will highlight some misleading interpretations of thermal lensing experiments due to the use of the dn/dT parameter in a context where it is not relevant. Part IV will be devoted to a state-of-the-art of experimental techniques used to measure thermal lensing. Eventually, in part V, we will give some concrete examples in Yb-doped materials, where their peculiarities will be pointed out.