Active Optical Fibers and Components for Fiber Lasers Emitting in the 2-μm Spectral Range
Filip Todorov, Jan Aubrecht, Pavel Peterka, O. Schreiber, A.A. Jasim, Jan Mrázek, Ondřej Podrazký, Michal Kamrádek, K. Nithyanandan, Martin Grábner, Yauhen Baravets, Jakub Cajzl, Pavel Koška, Adam Fišar, Ivan Kašı́k, Pavel Honzátko
Abstract
Laser sources emitting in the infrared range at around 2 µm are attracting great interest for a variety of applications like processing of transparent thermoplastic polymers in industry as well as plenty of applications in medicine, spectroscopy, gas sensing, nonlinear frequency conversion to the mid-infrared, to mention a few. Of late, fiber lasers compared to other kinds of lasers benefit from their all-fiber design, leading to a compact, robust, and well thermally manageable device. Particularly, thulium- and holmium-doped fiber lasers are the first choice in fiber lasers emitting light around 2 µm. In this paper, we give an overview of our recent results in the research on thulium- and holmium-doped optical fibers, fiber lasers, and related research topics in the 2-µm spectral range. In particular, we present, to our knowledge, the first results of improvement of pump absorption in double-clad fibers thanks to the fiber twist frozen during drawing. Finally, a brief demonstration of material processing by thulium all-fiber laser operating at 2 µm is presented.