A multistep pulse compressor (MPC) based on a single-pass single-grating-pair (SSGP) is proposed to simplify the entire multi-petawatt (PW) compressor. Only one grating pair with relatively long perpendicular distance is used to generate the same amount of spectral chirp compared with a fourgrating main compressor. As SSGP compressor induces the largest spatial chirp, it can introduce the best beam-smoothing effect to the laser beam on the last grating. When considering the diffraction loss of only two gratings, the total compression efficiency of the SSGP compressor is even larger than that of a four-grating main compressor. Furthermore, the wavefront aberration induced by SSGP compressor can be better compensated by using deformable mirrors, however it is difficult or complicated to be well compensated in a four-grating compressor. Approximately 50-100 PW laser pulses can be obtained using this SSGP-based multistage-smoothing MPC with a single laser beam.

High-performance 86 μJ, 11.2 fs pulses with a spectrum range of 800-1050 nm are generated based on 1030 nm, 190 fs Yb femtosecond pulses by using multi-plate based spectral broadening and filtering. Taking advantage of single beam configuration, the obtained pulses own excellent power and spectral stabilities. Since the output spectrum is obtained by spectrally filtering the broadened components, the temporal contrast of output pulses is enhanced by at least four orders of magnitude. Together with the robust and simple setup, the proposed method is expected to be a competitive option for the generation of seed pulses for 10s-100s petawatt lasers.

An improved single-shot fourth-order auto-correlator for temporal contrast measurement is proposed, in which spectral broadening based on self-phase modulation, followed by spectral filtering, is used for sampling pulse generation. When the input pulse energy is 5.5 mJ, the device has a measurement dynamic range of 3 × 10−11, a temporal resolution of approximately 200 fs, and a time window of 68 ps in a single shot. In addition, benefiting from the sCMOS camera data acquisition system, the measurement accuracy is self-verified using simply a tilted glass plate in the optical path of the sampling pulse. Since there is only one input beam without spatiotemporal overlap during sampling pulse generation, the setup is stable and easy to adjust.