Wavelength flexible, kW-level narrow linewidth fibre laser based on 7GHz PRBS phase modulation

We report on the results of a narrow linewidth fibre laser with >1kW laser output. Pseudo-random bit sequence (PRBS) phase modulation at 6.9GHz was employed to suppress Stimulated Brillouin Scattering (SBS). The laser demonstrated wavelength tunable operation from 1036nm to 1071nm, with spectral purity exceeding 40dB over most of the range. A delivery fibre length of 3m was enabled by exploiting the short gain lengths in a customized 250 mu m cladding fibre design. Near diffraction limited beam quality of M-2=1.19 was measured with no indication of transverse modal instability (TMI).