Synthesis of fully continuous phase screens for tailoring the focal plane irradiance profiles

In laser driven inertial confinement fusion systems, it is desirable to produce smooth focal plane intensity profiles [1]. Traditionally, binary random phase plates (RPPs) have been used to produce a focal plane irradiance profile which consists of a smooth Airy function shaped envelope and a superimposed fine scale speckle pattern. The speckle is smoothed by conduction smoothing in the laser produced plasma and/or by externally imposed temporal smoothing methods. Although easy to fabricate and use, the RPPs have very limited flexibility in producing arbitrary shaped irradiance profiles. In addition, the secondary maxima of the Airy profile lead to a 15% loss of the energy from the desired region in the focal plane. This loss of the laser energy requires the operation of the fusion lasers at higher energies thereby increasing their cost of operation. Additionally the scattered energy could also cause optical damage to detection equipment near the target.