A new method to improve the contrast ratio of fs ultra-intense laser pulses

Based on recent progress in chirped pulse amplification (CPA) techniques, we describe several new methods to improve the contrast ratio of ultra-intense laser pulses, for example by means of spatial filtering, temporal filtering, improving the contrast ratio of the seed, ring-cavity regenerative amplification, optical parametric CPA, double-CPA, and temporal filtering using nonlinear crystals. Through these new techniques the contrast ratio of ultra-intense laser pulses has been successfully increased to 1011.