  High power fiber lasers operating at the 1.5micron wavelength region have
attractive features like eye-safety and atmospheric transparency, and cascaded
Raman fiber lasers offer a convenient method to obtain high power sources at
these wavelengths. A limitation to power scaling however has been the lower
conversion efficiency of these lasers. We recently introduced a high efficiency
architecture for high power cascaded Raman fiber lasers applicable for
1.5micron fiber lasers. Here we demonstrate further power scaling using this
new architecture. Using numerical simulations we identify the ideal operating
conditions for the new architecture. We demonstrate a high efficiency 1480nm
cascaded Raman fiber laser with an output power of 301 W, comparable to record
power levels achieved with rare-earth doped fiber lasers in the 1.5 micron
wavelength region.
