Generation of a high-energy picosecond laser pulse with a high-contrast ratio by chirped-pulse amplification

The generation of a 1.052- mu m laser pulse of 3.5-ps duration and 28-J energy by fiber-grating chirped-pulse amplification in a large-aperture Nd-glass laser system is reported. A novel technique that significantly improves the contrast ratio was used, resulting in a pulse with 8-TW peak power and a contrast ratio of better than 900, limited by the dynamic range of the detection system. The high contrast ratio was obtained by selecting only only the central portion of the frequency-chirped pulse where the chirp is positive and linear. The high-intensity compressed pulse thus generated was frequency-upconverted to 526 nm with a 40% conversion efficiency.< >