Fig. 1. Experimental setup of the high-power linearly polarized CPA system. ISO, isolator; Cir, circulator; CFBG, chirped fiber Bragg grating; LD, laser diode; WDM, wavelength division multiplexer; PM YDF, polarization-maintaining Yb-doped fiber; CO, collimator.

Fig. 2. The laser properties of the seed pulse: (a) output spectrum; (b) pulse train.

Fig. 3. (a) Output spectrum after two cascaded CFBGs. (b) Pulse waveforms after the two cascaded CFBGs, pre-amplifier 1 and pre-amplifier 2.

Fig. 4. Output characteristics of the main amplifier: (a) average power and single pulse energy as a function of the pump power; (b) output spectra at selected output power; inset: linear-scale spectrum at the highest power; (c) pulse waveform at the highest power; (d) evolution of the polarization degree with the enhancement of the output power.

Fig. 5. (a) Beam quality of the main amplifier at the selected operating power; (b) M² factor at the output power of 612 W.

Fig. 6. Autocorrelation traces of the compressed pulse at the highest output power (a) without and (b) with fine adjusting of the higher-order dispersion of the CFBG.