Some applications like range finding, optical counter measures or engine ignition, require lasers capable of delivering high repetition rate bursts of nanosecond pulses with hundreds of microjoules to a few millijoules in terms of energy per pulse. We have developed such a diode pumped Yb:YAG micro-laser with an oscillator comprised of a 2-mm long 10% at. doped Yb:YAG crystal followed by a Cr:YAG passive Q-switch with an initial transmittance of 85 %. The laser planoconcave cavity is 5-cm long. This oscillator emits 250 μJ to 300 μJ per pulse, with a 3 – 5 ns pulse duration, with an intra-burst pulse repetition frequency that can be tuned continuously from 1 kHz to 20 kHz by increasing the pump power. The pumping diode laser is operated in quasi continuous wave regime, emitting 1-ms to 10-ms long pulses with up to 20 W peak power This qcw pumping results in the emission of a burst of pulses at high repetition rate for the duration of this pump long pulse. These pump pulses, and consequently the bursts of nanosecond pulses, are repeated at very low frequency, between 1 Hz and 5 Hz, so that the average power to handle doesn’t require active cooling. This oscillator is then amplified to the millijoule level in a second 3-mm long Yb:YAG crystal pumped by a synchronous qcw emitting diode laser.
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