Abstract

Multi-stage glass laser systems used in high temperature plasma generation, for applications such as inertial confinement fusion, ICF, require very well defined laser pulses to be propagated and focused on target. Efficient energy extraction is a significant factor in modem high power lasers used for ICF research such as NIF in the US, LMJ in France and the modified HELEN laser in the UK. Multi-passing techniques are employed to make most effective use of the stored energy. Control of the laser amplitude and phase distributions becomes more difficult in such systems. We have applied phase elements in two different ways to achieve better control of the laser pulses. Firstly, we describe static phase correction elements to compensate for thermally induced aberrations and secondly, we show how phase elements may be used to modify the intensity distribution of the laser beams in intra– and extra–cavity configurations. The phase elements are fabricated through lithographic processes using amplitude masks. The masks arc either generated from measured laser wavefronts or beam propagation calculations.

© 2000 IEEE