Shock ignition is a relatively new approach to inertial fusion energy which seeks to heat fusion fuel more efficiently. Unlike fast ignition, which employs exceptionally high-intensity laser pulses, shock ignition endeavours to achieve high efficiency with laser intensities that are not dramatically higher those already employed in ignition scale laser facilities such as the National Ignition Facility in California, and Laser MegaJoule in France.
Shock ignition achieves its enhanced efficiency by depositing much of the laser energy late in time, at which point in time much of the original mass of the fuel capsule has been vapourised, and is at such low density that the laser does not significantly interact with it. This results in the laser coupling more effectively to the 'important' part of the fuel capsule: the fuel itself. The shock ignition approach was first pioneered by the Laboratory for Laser Energetics at the University of Rochester, but has since become a key area of exploration for laboratories in Europe.