Single mode laser diode based compact seed source for continuous wave Yb-Raman fiber amplifier with enhanced higher order Raman suppression.

In this paper, we demonstrated a novel seed source for the continuous wave Yb-Raman fiber amplifier, which adopted an 1140 nm single mode laser diode (LD) as Raman signal seed and a conventional 1085 nm fiber oscillator as the Raman pump seed. By splicing a section of long passive fiber in the Raman pump seed cavity, optimizing the Raman pump seed power and the cooling condition, the higher order Raman threshold was doubled and over 500 W output Yb-Raman fiber amplifier was achieved. In addition, our experiment also proved that, for the first time, splicing long passive fiber in the seed oscillator cavity improved the temporal performance of the first order Raman in the conventional fiber master oscillator power amplifier, which could increase the higher order Raman threshold as a result. The seed structure based on a single mode LD and a long cavity length fiber oscillator, could provide a highly compact and cost effective seed source for the high power Yb-Raman fiber amplifier with enhanced higher order Raman suppression. [ABSTRACT FROM AUTHOR]