In-fiber polarizer based on a 45-degree tilted fluoride fiber Bragg grating for mid-infrared fiber laser technology

We report the direct femtosecond laser inscription of a 45 degrees tilted fiber Bragg grating (TFBG) into fluoride fiber, creating an in-fiber mid-infrared polarizer. Utilizing a 16 mm long intracavity TFBG, we demonstrate a 2.862 mu m Ho3+Pr3+:ZBLAN fiber laser with 21.6 dB output polarization extinction ratio (PER), up to 0.37 W output power and 31.3% slope efficiency. In addition, we experimentally demonstrate that the laser PER is a linear function of grating length. Our results show that fluoride TFBGs are a promising route to replace bulk polarizers in mid-IR laser cavities, paving the way to all-fiber mid-infrared laser systems. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement