Crystalline fiber Ho3+:YAG laser resonantly pumped by high-spectral-brightness laser diodes

Antoine Berrou; Thierry Ibach; Martin Schellhorn; Wentao Hu; Robert Lammert; Laurent Vaissié; Jeff Ungar; Marc Eichhorn

doi:10.1117/12.906657

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15 February 2012 Crystalline fiber Ho³⁺:YAG laser resonantly pumped by high-spectral-brightness laser diodes

Antoine Berrou, Thierry Ibach, Martin Schellhorn, Wentao Hu, Robert Lammert, Laurent Vaissié, Jeff Ungar, Marc Eichhorn

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Proceedings Volume 8235, Solid State Lasers XXI: Technology and Devices; 823518 (2012) https://doi.org/10.1117/12.906657
Event: SPIE LASE, 2012, San Francisco, California, United States

Abstract

Recent advances of high power and narrow bandwidth laser diodes emitting at 1.9 μm open the path to direct diode pumping of Ho³⁺:YAG lasers. The usual method to pump such laser is to use thulium fiber laser which has an excellent beam quality with high power and narrow bandwidth emission. The draw back of this system is the low efficiency of this fiber laser and the increased overall complexity. In this paper we present first results of resonantly diode pumping of a Ho³⁺:YAG laser with fiberlike geometry. The fiber coupled diode modules used for pumping in this work (BrightLock^TMUltra-500) produce each 25 W at 1.91 μm with 3 nm linewidth. The fiber has a core diameter of 600 μm with 0.22 numerical aperture. The Ho³⁺:YAG crystal has a diameter of 1.2 mm, a length of 60 mm, a doping concentration of 0.75 at.% and is symmetrically pumped by two diode modules from both ends. Total internal reflection on the polished rod barrel allows a high pump intensity along the rod length. The Ho³⁺:YAG laser cavity is composed of a high reflective flat mirror and a concave output coupler with a radius of curvature of 500 mm. With an output coupler of 50 % we measured a threshold of 11 W. The maximum output power was 11.87 W with a wavelength of 2.09 μm. The incident power to output power slope efficiency was 0.38 at currently 4 % of internal losses.

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Antoine Berrou, Thierry Ibach, Martin Schellhorn, Wentao Hu, Robert Lammert, Laurent Vaissié, Jeff Ungar, and Marc Eichhorn "Crystalline fiber Ho³⁺:YAG laser resonantly pumped by high-spectral-brightness laser diodes", Proc. SPIE 8235, Solid State Lasers XXI: Technology and Devices, 823518 (15 February 2012); https://doi.org/10.1117/12.906657

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