1kW Narrow-Linewidth CW Fiber Laser Source for Spectral Beam Combining

We present the design and development of a packaged, narrow-linewidth high power fiber laser module with output power of 1 kW as the source for Spectral Beam Combining. This is a cladding pumped single mode ytterbium doped fiber laser in a MOPA configuration with slope efficiency of 87% generating 1 kW of continuous wave power, at 1060 nm with a linewidth of 15 GHz and SNR of 30 dB. A MHz linewidth seed laser is line broadened to 15 GHz through phase modulation using white noise source and then further amplified to kW power through three amplifier stages. We also report the various experimental investigations on line broadening techniques and building process optimizations in order to improve the spectral quality.