Efficient Spherical Wavefront Correction near the Focus for the 0.89 PW/29.0 fs Ti:Sapphire Laser Beam

We demonstrate a new loop system of the spherical wavefront(SW)correction near the beam focus to effectively improve the focusability of 0.89 PW/29.0 fs Ti:sapphire chirped pulse amplification laser.After wavefront correction,the Strehl ratio is improved to reach 0.91,and the focal spot size using the f/4 off-axis parabola is reduced to 6.34 x 6.94μm^(2)(corresponding to 1.63 x 1.78 times diffraction limitation).With full peak power of 0.89 PW,the peak intensity of 2.59 x 10^(21)W/cm^(2)is obtained.The experimental results show that the SW correction scheme near the beam focus is comparatively simple,economic and high-efficient.