High-efficiency 50 W burst-mode hundred picosecond green laser

We report high-energy, high-efficiency second harmonic generation in a near-infrared all-solid-state burst-mode picosecond laser at a repetition rate of 1 kHz with four pulses per burst using a type-I noncritical phase-matching lithium triborate crystal. The pulses in each burst have the same time delay (similar to 1 ns), the same pulse duration (similar to 100 ps) and different relative amplitudes that can be adjusted separately. A mode-locked beam from a semiconductor saturable absorber mirror is pulse-stretched, split into seed pulses and injected into a Nd:YAG regenerative amplifier. After the beam is reshaped by aspheric lenses, a two-stage master oscillator power amplifier and 4f imaging systems are applied to obtain a high power of similar to 100 W. The 532 nm green laser has a maximum conversion efficiency of 68%, an average power of up to 50 W and a beam quality factor M-2 of 3.5.