Ultrahigh-contrast kilojoule-class petawatt LFEX laser using a plasma mirror

Laser pulse contrast exceeding 1011 was demonstrated on a kilojoule-class petawatt laser for fast ignition experiments (LFEX) laser system [J. Phys. IV France 133, 81 (2006)] by implementing a 2 in. plasma mirror. Laser beams of up to 1.2 kJ striking the plasma mirror with a pulse duration of 1.5 ps were reflected and focused onto a target without significant distortions in the focal spot. Transmitted light from the plasma mirror reveals that it has a high reflectivity 2 ps before the main peak. The estimated laser pulse contrast at the target was 1011 at 1 ns before the main peak. No preformed plasma was observed with optical interferometry diagnostics, but in the experiment without a plasma mirror a preplasma was clearly observed. The energetic proton was generated from a 0.1 mu m thick CH film showing excellent pulse contrast. This technique constitutes a promising method to enhance the LFEX laser system performance in fast ignition experiments. (C) 2016 Optical Society of America