Production Techniques of Phase Plates for Laser Focal Spot Smoothing

摘要

In high power lasers such as the VULCAN Nd:glass laser system at the RutherfordAppleton Laboratory (RAL), the quality of the focal spot is a critical issue for the laser-plasma interaction studies. Beam smoothing techniques have therefore had to be developed to overcome these undesirable phase and amplitude modulation problems. Kato et al developed the random phase plate (RPP) in order to provide a means to scramble the phase of a laser beam and thereby cause a smoothing effect. This method was then employed in order to increase the quality of data gained from laser-plasma interaction experiments. Deng et al developed an alternative technique using an array of refracting lenses to split the beam into many separate beamlets. A combination of these two techniques, the phase zone plate array (PZP), was developed at RAL in collaboration with researchers from AWE plc. This report describes the techniques developed at RAL to manufacture both the RPP and PZP plates.