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 ? 6.94 ?m2 (corresponding to 1.63 ? 1.78 times diffraction limitation). With full peak power of 0.89 PW, the peak intensity of 2.59 ? 1021 W/cm2 is obtained. The experimental results show that the SW correction scheme near the beam focus is comparatively simple, economic and high-efficient.