We proposed a novel method, using an asymmetric four grating compressor
(AFGC) to improve the spatial uniformity of laser beams, to suppress the
small-scale self-focusing (SSSF) during the post-compression of ultrahigh peak
power lasers. The spatial uniformity is an important factor in performing
post-compression, due to the spatial intensity nonuniformity will be enhanced
while going through a nonlinear process. And what's more, the strong intensity
spikes induced during nonlinear process can seriously damage the subsequent
optical components. Moreover, the three-dimensional numerical simulations of
the post-compression are implemented based on a petawatt (PW) class laser with
a standard compressor and an AFGC. The results show that the post-compression
with AFGC can shorten the laser pulses from 30fs to sub-10fs and meanwhile
efficiently suppress SSSF. This work provides a promising scheme for the
post-compression scaling to PW and even 10PW lasers