Efficient second harmonic generation in a KDP crystal pumped with picosecond YAG:Nd3+ laser pulses of 0.5 Hz repetition frequency

Frequency doubling in a KDP crystal, pumped with single pulses of 30 psec duration, was optimized. It was found that, under picosecond pumping conditions, there was a definite optimal relationship between the length of a crystal and pump power density. The energy efficiency of conversion to the second harmonic was 92% for a pump power density of 8×10⁹ W/cm² in a crystal 14 mm long.