A study of ambient upstream material properties using perpendicular laser driven radiative blast waves in atomic cluster gases

We report on the characterisation of the upstream medium ahead of a radiative cylindrical blast wave launched in an argon cluster gas with a 1 J, 1 ps, 1054 nm Nd:Glass laser system. By launching two perpendicular blast waves and introducing a time delay between the heating beams it is possible to determine the extent of the cluster medium by observing the high energy absorption region associated with clusters, as apposed to the low energy deposition in monatomic gas. It was found that argon ions launched from the initial laser driven cluster ionisation created a ballistic ion wave which sweeps out ahead of the hydrodynamic blast wave at an initial velocity of 1000 kms -1. This ballistic wave disassembles the clusters ahead of the blast wave into a neutral gas medium before the arrival of a radiative precursor. This observation gives us confidence that the dynamics of a radiative blast wave in cluster based experiments is determined primarily by the properties of an upstream atomic gas, and is not significantly influenced by cluster affects on energy transport or other material properties. © 2011 Elsevier B.V

Spectral enhancement in optical parametric amplifiers in the saturated regime

We present numerical and experimental studies on a front-end laser system for seeding a sub-picosecond multi-terawatt/petawatt light source based on two highly saturated optical parametric amplifiers. Numerical results showing energy gain, spectral gain, and stability as saturation is approached are presented. An experimental realisation of the system has been constructed, and its performance has been found to be in good agreement with the numerical simulations. The total gain is in excess of 105 over a few picosecond gain window, and the pulse energy is ∼100 μJ with 4 % root mean square stability. © 2013 Springer-Verlag Berlin Heidelberg