Micro-lens arrays were adopted to homogenize the beam profile of 532-nm pumping laser for the main amplifier of an intense femtosecond, chirped pulse amplification (CPA) Ti:sapphire laser. Experimental measurements showed a great improvement of the near-field pattern of the CPA beam after the main amplifier and the size of the focal spot was improved from 2.7 times diffraction limitation (DL) to 1.6 DL. The spot size focused by an f/4 off-axis parabola (OAP) in the target chamber was measured to be 5.8 micron (full-width at half-maximum (FWHM)), and a peak intensity of 2.6*10^(20) W/cm2 was obtained at the output power of 120 TW. Peak intensity exceeding 10^(21) W/cm2 or even 10^(22) W/cm2 can be expected with smaller f-number focusing configuration and wavefront correction.

Electron acceleration in a tightly focused ultra-intensity linear polarized laser beam is investigated numerically. It has been found that the acceleration is strong phase dependent and is periodic to the variety of the initial laser field phase. When optimal initial parameters are chosen, the electron can be accelerated effectively. The accelerated electrons are emitted in pulses of which the full width is less than the half period of the laser field.