Single-mode millijoule fiber laser system with high pulse shaping ability

Abstract The coherent amplification network (CAN) aims at developing a laser system based on the coherent combination of multiple laser beams, which are produced through a network of high beam quality optical fiber amplifiers. For the front-end sources of high power laser facilities, single-mode linearly polarized beams in the nanosecond time scale are required. According to these two requirements, a millijoule polarized fiber laser system was studied. Using polarization maintaining Ytterbium-fiber laser system as the seed, 10-μm core diameter Yb-doped fiber amplifier as the first-stage power amplifier and 40-μm core diameter polarizing photonic crystal fiber (PCF) as the second-stage power amplifier, the all-fiber laser system output 1.06-mJ energy at 10 ns with diffraction limited mode quality. Using 85-μm core diameter rod-type PCF as the third-stage power amplifier, 2.5-mJ energy at 10-ns pulse width was obtained with better than 500:1 peak-to-foot pulse shaping ability and single-mode beam quality. The energy fluctuation of the system was 1.3% (rms) with 1-mJ output in an hour. This fiber laser system has the advantages of high beam quality, versatile pulse shaping ability, good stability, small volume, and free of maintenance, which can be used in many applications.