High brightness narrow-linewidth microsecond pulse green laser by frequency doubling of a master oscillator power amplifier Nd:YAG laser

We demonstrated a high brightness narrow-linewidth microsecond (μs) pulse green laser from second harmonic generation (SHG) of a master oscillator power amplifier (MOPA) laser system. The oscillator was a quasi-continuous wave pulsed diode-side-pumped 1064 nm Nd:YAG laser with an average output power of 45.2 W and a beam quality factor of M2 = 1.21, operating at a pulse repetition frequency of 500 Hz with a ∼160 μs of pulse duration. After a two-stage amplifier, the fundamental output power of MOPA system was increased up to 198 W. Using a type-I lithium triborate nonlinear crystal, the maximum SHG output power of 78.4 W at 532 nm was obtained with a linewidth of 0.54 pm and a beam quality factor M2 less than 1.61. The brightness of the green light was as high as 1.08 × 1010 W/cm2 sr. This is, to the best of our knowledge, the highest brightness solid state light source for the narrow-linewidth μs pulse green lasers at 532 nm.