Single plasma mirror providing 104 contrast enhancement and 70% reflectivity for intense femtosecond lasers.

To efficiently eliminate picosecond pre-pulses that accompany ultrashort pulses emitted from high-power chirped-pulse-amplification laser systems, we have developed a high-performance plasma mirror system. By reducing the reflectivity of the antireflection coating on the substrate for the plasma mirror to the limit of current technology (∼0.006%), we achieved the highest pre-pulse contrast enhancement reported to date for a single plasma mirror of 104 at 1 ps before the pulse peak. By optimizing the laser incidence to the plasma mirror and the laser fluence, the reflectivity of the plasma mirror has been improved to 70%. The contrast improvement indicates extensibility to 100 PW class lasers by doubling this plasma mirror system. Contrast enhancement of 108 should be possible without a serious reduction in energy (no more than 50%).