Subpicosecond pre-plasma dynamics of a high contrast, ultraintense laser-solid target interaction.

Using the spectral interferometry technique, we measured subpicosecond time-resolved pre-plasma scale lengths and early expansion (<12 ps) of the plasma produced by a high intensity (6 × 1018 W/cm2) pulse with high contrast (109). We measured pre-plasma scale lengths in the range of 3-20 nm, before the arrival of the peak of the femtosecond pulse. This measurement plays a crucial role in understanding the mechanism of laser coupling its energy to hot electrons and is hence important for laser-driven ion acceleration and the fast ignition approach to fusion.

Efficient second-harmonic generation of a high-energy, femtosecond laser pulse in a lithium triborate crystal.

We demonstrate the highest efficiency (∼80%) second harmonic generation of joule level, 27 fs, high-contrast pulses in a type-I lithium triborate (LBO) crystal. In comparison, potassium dihydrogen phosphate gives a maximum efficiency of 26%. LBO thus offers high-intensity (>1018-19W/cm2), ultra-high contrast femtosecond pulses, which have great potential for high energy density science and applications, particularly with nanostructured targets.