Abstract

Fiber lasers operating at 2µm wavelength range have great potential in applications like coherent LIDAR [1] and remote sensing [2]. In particular, the 2.09~2.1μm range exhibits low atmosphere attenuation [1]. The 2µm region could also be a new window for optical communication in hollow core fibers [3], where narrow linewidth and linearly polarized light is preferred. Efficient 2µm range lasing has already been demonstrated with both holmium (Ho) [4] and thulium (Tm) doped fiber lasers [5] reaching 2.2µm. However, these lasers cannot directly provide linearly polarized light, and inserting a polarizer in the cavity dramatically reduces the slope efficiency. Also, the widely used linear cavity for long wavelength lasing requires careful selection of the output coupling ratio for optimized lasing at a single wavelength. Here, we report an efficient Ho-doped polarizer-free all-fiber laser with linearly polarized output. Utilizing a broadband fiber loop mirror, the output coupling can be continuously tuned, allowing the optimization of output power while covering the whole Ho and Tm band.

© 2017 IEEE