Frequency doubling of dual frequency injection seeding laser pulses

High power RF intensity modulated pulses at 532 nm are achieved via dual-frequency injection seeding a Q-switched laser at 1064 nm and frequency doubling. A dual-frequency laser signal with beat-note frequency of 200 MHz is injected into a Q-switched Nd:YAG laser cavity, the injected power is 40 mW, two adjacent longitudinal modes of the cavity with mode spacing from 223 to 227 MHz are locked to the injected signal respectively. The output pulses are RF intensity modulated due to the interferences between the two modes. By changing the power transmission index of the output coupler of the Q-switch laser, the pulse durations from 16 ns to 20 ns are observed. When the transmission of the output coupler is 44%, the pulse energy is 7 mJ and pulse width is 16 ns, corresponding a peak power of 437 kW. The RF modulated laser pulse at 1064 nm is frequency doubled by a KTP crystal. The SHG pulse energy is 2.27 mJ with a pulse duration of 12 ns, corresponding to a peak power of 189 kW. Two modulation frequencies at 223 MHz and 446 MHz are observed in the second harmonic wave. The high-power RF intensity modulated pulsed light source at 532 nm has potential applications in long-distance underwater detections.