Plasma-based beam combiner for very high fluence and energy

Extreme optical fluences, much beyond the damage threshold of conventional optics, are of interest for a range of high-energy-density physics applications. Nonlinear interactions of multiple beams in plasmas have the potential to produce optics that operate at much higher intensity and fluence than is possible in solids. In inertial confinement fusion experiments indirectly driven with lasers, many beams overlap in the plasma inside a hohlraum, and cross-beam energy transfer by Brillouin scattering has been employed to redistribute energy between laser beams within the target. Here, we show that in a hot, under-dense plasma the energy of many input beams can be combined into a single well-collimated beam. The emerging beam has an energy of 4 kJ (over 1 ns) that is more than triple that of any incident beam, and a fluence that is more than double. Because the optic produced is plasma, and is diffractive, it is inherently capable of generating higher fluences in a single beam than solid-state refractive or reflective optics. In a hot, under-dense plasma, eight input beams are combined into a single, well-collimated beam, whose energy is more than triple than that of any incident beam. This shows how nonlinear interactions in plasmas can produce optics beams at much higher intensity than possible in solids.