@article{Aydin:19,
author = {Yigit Ozan Aydin and Fr\'{e}d\'{e}ric Maes and Vincent Fortin and Souleymane T. Bah and R\'{e}al Vall\'{e}e and Martin Bernier},
journal = {Opt. Express},
keywords = {Fiber lasers; High power fiber amplifiers; High power fiber lasers; High power lasers; Laser sources; Laser systems},
number = {15},
pages = {20659--20669},
publisher = {OSA},
title = {Endcapping of high-power 3 \&\#x00B5;m fiber lasers},
volume = {27},
month = {Jul},
year = {2019},
url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-27-15-20659},
doi = {10.1364/OE.27.020659},
abstract = {Fiber tip photodegradation through OH diffusion currently limits the long term operation of high-power fiber lasers and amplifiers operating near 3\&\#x2009;\&\#x00B5;m. To address this issue, we investigate the resistance to OH diffusion of fluoride and oxide endcaps manufactured out of ZrF\$_4\$4, AlF\$_3\$3, GeO\$_2\$2, SiO\$_2\$2 and Al\$_2\$2O\$_3\$3 fibers. To this extent, the endcaps are spliced at the output of a 20\&\#x2009;W continuous-wave fiber laser operating at 2.8\&\#x2009;\&\#x00B5;m and their degradation over a 100\&\#x2009;h time period is monitored. While the fluoride-based endcaps underwent failure during the first 10\&\#x2009;h, their oxide counterparts survived the experiment, although showcasing degradation which was reflected as an increase of the endface temperature over time. To overcome this issue, we propose a novel method to completely suppress OH diffusion which consists in sputtering a nanoscopic diffusion barrier film made of silicon nitride (Si\$_3\$3N\$_4\$4) on the output face of the endcap. The effectiveness of the approach is validated on Al\$_2\$2O\$_3\$3, ZrF\$_4\$4 and AlF\$_3\$3 endcaps which show no sign of degradation after being used for more than a 100\&\#x2009;h at the output of a 3\&\#x2009;\&\#x00B5;m high-power fiber laser.},
}