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Proceedings Paper

Thermal effects and upconversion in the Er3+:YAG solid-state heat-capacity laser
Author(s): Marc Eichhorn
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Paper Abstract

Although seen as nearly being impossible to realize, a quasi-three-level laser medium can be used in heat-capacity operation. In this operation mode, the laser medium is not cooled during lasing in order to avoid strong thermal lensing, which, in actively cooled operation, would result in a low beam quality or would even destabilize the laser cavity. Thus, in heat-capacity mode, the laser medium will substantially heat up during operation, which will cause an increase in re-absorption for a quasi-three-level laser medium, resulting in a general drop in output power over time. However, laser power, temperature rise, fluorescence and inversion are coupled by the temperaturedependent spectroscopic properties of the laser medium in a complex way. This paper presents an investigation on these thermal effects and upconversion in the resonantly pumped Er3+:YAG solid-state heat-capacity laser (SSHCL) system. These effects are important for the scaling properties on this laser towards medium- or high-energy systems, and to obtain a good beam quality from the laser itself. It is shown that the expected power drop of this quasi-three-level medium due to the rise in crystal temperature is very low, allowing for high-power operation on substantial time scales. The experimental results and the theoretical background will be explained in detail. The effect of fluorescence re-absorption on the laser properties, especially on threshold and laser efficiency will also be discussed. This fluorescence re-pumping, applicable in general to a large variety of lasers, can drastically increase the output power and thus laser efficiency at a given pump power. Up to 125 W and 89 J in 2 s are achieved using optimized doping levels for upconversion reduction.

Paper Details

Date Published: 12 October 2010
PDF: 12 pages
Proc. SPIE 7836, Technologies for Optical Countermeasures VII, 783608 (12 October 2010); doi: 10.1117/12.864433
Show Author Affiliations
Marc Eichhorn, Institut Franco-Allemand de Recherches de Saint-Louis (France)

Published in SPIE Proceedings Vol. 7836:
Technologies for Optical Countermeasures VII
David H. Titterton; Mark A. Richardson, Editor(s)

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