High power sub-ps pulse generation by compression of a frequency comb obtained by a nonlinear broadened two colored seed

Frequency combs with large line spacing have many applications and are under intense research. Methods for generating such combs either start with initial frequency spaced lasers (like combined single-frequency lasers, phase- and amplitude modulated lasers or mode-locked-laser) or employ nonlinear effects to start or extend its spectral bandwidth in fibers or micro cavities [1-3]. Here we demonstrate the generation of a frequency comb of several nm widths with arbitrary frequency spacing from ~50 GHz to 500 GHz by four-wave-mixing (FWM) of two external cavity lasers (EDCL) combined amplified in a high power large-mode area fiber amplifier. The power levels demonstrated are in the range of several 100 W to 4 kW. We also demonstrate that in the temporal picture, pulses of multiple kW peak power can be generated by compressing the output beam.