Frequency doubling a 140 × 110 mm 40 J sub-ps
1054 nm beam for laser matter interaction studies was investigated
at the Central Laser Facility, with efficiencies greater
than 60% being achieved. The conversion characteristics
(efficiency, beam quality, focusability, and pulse length)
for two large 157 mm diameter aperture high quality KDP
crystals of thickness 2 mm and 4 mm were studied. Using
a fundamental drive beam of two times diffraction limited
quality, focal spots of four times the diffraction limit
in the frequency doubled beam were achieved and beam degradation
effects shown to be minimal.