Wavefront Correction in Vacuum of SULF-1PW Laser Beamline

We report here an improvement of the focusing quality of SULF-1PW laser beamline, planning to drive and generate 5~10 GeV electron beams. After the wavefront correction in vacuum with an adaptive optical system and the focusing with an f/56 off-axis parabolic mirror, near diffraction-limited focal spots with a size of 52 × 54 μm2 at full width at half maximum are achieved, and the enclosed energy inside this size is ~36.6%. Consequently, the focused intensity of ~1.66×1019 W/cm2 can be achieved at 1 PW peak power. Moreover, we also examine the wavefront stability in air and vacuum respectively. From the statistical analysis of 1900 shots successive laser pulses at 1 Hz, we identify the wavefront fluctuation resulted from air turbulence and the better correction capacity in vacuum. This work demonstrates the importance and necessity of the wavefront correction in vacuum for high peak power lasers.