980-nm random fiber laser directly pumped by a high-power 938-nm laser diode

A random lasing based on Rayleigh scattering in a passive fiber directly pumped by a high-power laser diode (LD) has been demonstrated. Owing to the random distributed feedback (RDFB) the low-quality LD beam (938 nm) is converted into the high-quality laser output (980 nm). Because of the relatively low excess above the threshold with the available LD, the RDFB laser output is limited in power on 0.5 W level. In the used gradient-index (GRIN) fiber the output beam has 4.5 lower divergence as compared with the pump beam thus demonstrating a new approach for high-power fiber lasers with high-quality output.