  We demonstrate a new high efficiency architecture for cascaded Raman fiber
lasers based on a single pass cascaded amplifier configuration. Conversion is
seeded at all intermediate Stokes wavelengths using a multi-wavelength seed
source. A lower power Raman laser based on the conventional cascaded Raman
resonator architecture provides a convenient seed source providing all the
necessary wavelengths simultaneously. In this work we demonstrate a 1480nm
laser pumped by an 1117nm Yb-doped fiber laser with maximum output power of
204W and conversion efficiency of 65% (quantum-limited efficiency is ~75%). We
believe both the output power and conversion efficiency (relative to
quantum-limited efficiency) are the highest reported for cascaded Raman fiber
lasers.
