  Raman fiber lasers (RFLs) are currently promising and versatile light sources
for a variety of applications. So far, operations of high power and
brightness-enhanced RFLs have absorbed enormous interests along with rapid
progress. Nevertheless, the stable Raman lasing at high power levels remains
challenged by the thermal effects. In an effort to realize more effective
thermal management in high power RFLs, here we demonstrate, for the first time,
an all-fiberized RFA employing metal-coated passive fiber enabling high power
lasing. By employing aluminum to the cladding of graded-index (GRIN) passive
fiber, the thermal abstraction of the laser devices is more sufficient to
support low-temperature operation. The maximum output power reaches 3.083 kW at
1130 nm with a conversion efficiency of 78.7%. To the best of our knowledge,
this is the first Raman laser generation based on metal-coated passive fiber.
Meanwhile, it is also the highest power attained in the fields of all kinds of
Raman lasers based on merely nonlinear gain.

Optics