172-fs, 27-µJ, Yb-doped all-fiber-integrated chirped pulse amplification system based on parabolic evolution by passive spectral amplitude shaping

Parabolic pulses with linear self-phase-modulation-induced frequency chirp are attractive in ultrafast laser fiber amplification system for the functionality of nonlinearities suppression. In this paper, we present an effective way of parabolic pulse evolution by passive spectral amplitude shaping with a pair of chirped fiber Bragg gratings (CFBG). By this approach, a high-energy high-peak-power Yb-doped fiber chirped pulse amplification (CPA) system is demonstrated. The oscillator is a dispersion-managed passively mode-locked Yb-doped fiber laser with a broadband Gaussian-shaped spectrum which is evolved to parabola in a following preamplifier with pre-chirping management by a CFBG compressor. The pulses are then stretched with a CFBG stretcher, based on frequency-to-time mapping, the temporal profiles of the pulses show an identical parabolic envelope to the spectrum. The shaped pulses are further amplified with three stages of all-fiber amplifiers and compressed by a grating-pair compressor. The pulse duration is compressed to 172 fs with a pulse energy of 27 µJ. The central pulse encompasses 72% of total pulse energy, corresponding to a pulse peak power of 113 MW. No obvious pulse degeneration is noticed at nonlinearity accumulation B-integral as high as 12 rad. This configuration shows a significant potential for nonlinearity tolerance in high-energy operation compared with conventional CPA system.