Fig. 1. Experimental setup of the high-power CPA system based on the active polarization control technology. Cir, circulator; CFBG, chirped fiber Bragg grating; PC, polarization controller; PA, pre-amplifier; LD, laser diode; YDF, Yb-doped fiber; CO, collimator; PBS, polarization beam splitter; PD, photodetector.

Fig. 2. Output characteristics of the main amplifier. (a) Output power versus the pump power. (b) PER evolution with and without active polarization control. (c) Output spectra. (d) M² factor and corresponding beam profile at different output powers.

Fig. 3. Stability properties of the main amplifier at the output power of 402.3 W. (a) Temporal intensity fluctuations at the closed and open loop states. (b) RF spectrum at the fundamental repetition frequency. Inset: RF spectrum in the frequency range of 1 GHz.

Fig. 4. Noise properties of the main amplifier at the output power of 402.3 W. (a) PN and TJ in the frequency of 10 Hz–10 MHz. (b) RIN spectrum and integrated RIN in the frequency range of 100 Hz–1 MHz.

Fig. 5. Autocorrelation trace of the compressed pulse at the output power of (a) 43.2 W, (b) 192.6 W, and (c) 402.3 W. The blue and red curves, respectively, denote the measured and fitted autocorrelation traces.