Dynamic Focal Spot Size Using a Static Phase Plate

A distributed phase plate (DPP) is designed for the: University of Rochester Laboratory for Laser Energetics OMEGA laser system that can, manipulate the focal spot size during a three-nanosecond pulse. These hybrid full aperture diffractive elements alter the focal spot size to match the diameter of an imploding target. When implemented in the OMEGA system, these DPPs will greatly increase on-target energy efficiency in direct drive experiments. The OMEGA'S current focal spot diameter is unchanging during the beam pulse. Because of this, much of the energy misses the target after it shrinks from implosion. The newly modified DPPs have the ability to dynamically control the focal spot diameter on target to account for an imploding target. Simulated illumination shows that the new DPPs increase the late pulse percent intensity on-target from 27.5 % to 73.4%. They also produce an azimuthally symmetric and super-Gaussian intensity profile to maintain reasonable irradiation uniformity. Page I 2