Low threshold and high spectral purity 1.7 μm random fiber laser based on hybrid gain

Abstract

1.7 μm band lasers have shown great potential in various applications including gas monitoring and pumping mid-infrared lasers. However, due to the lack of an effective gain mechanism, the lasing performance of current sources in this band, in terms of the threshold, the spectral purity, as well as the reliability, is still inferior to their counterparts at ∼1 μm or ∼1.5 μm and hinders their actual applications. Here, we propose the first demonstration of an efficient 1.7 μm random fiber laser with hybrid gain in a common cavity structure to the best of our knowledge. In the hybrid gain approach, the lasing threshold is greatly reduced benefiting from the active gain of thulium fiber, while the optical efficiency is dramatically boosted accompanied by the nonlinear gain of stimulated Raman scattering. Besides, the optimized cavity design based on two backward pumped half-open cavities can produce a completely pure 1.7 μm lasing for the whole power scaling range. This work enriches the gain mechanism of the 1.7 μm band laser and provides high spectral purity and low lasing threshold as well as excellent robustness for realistic applications.