We report on a compact conductively cooled high-repetition-rate nanosecond Nd:YAG laser. The oscillator was an laser diode side-pumped electro-optical (EO) Q-switched Nd:YAG rod laser adopting unstable cavity with a variable reflectivity mirror. A pulse train of 142 mJ with duration of 10 ns, repetition rate of 80 Hz at 1064 nm has been achieved. Maximum pulse energy was obtained at the pump energy of 1380 mJ, corresponding to the optical–optical conversion efficiency of 10.3%. The peak power was deduced to be 14.2 MW. The near-field pattern demonstrated a nearly super Gaussian flat top profile. To our knowledge, this is the highest repetition rate operation for a conductively cooled EO Q-switched Nd:YAG rod laser.
Multilayer dielectric gratings (MDGs) are more and more used to compress pulse in the next generation
of chirped-pulse amplification (CPA) system for high-energy petawatt (HEPW)-class lasers due to their
high efficiency and high damage threshold for picosecond pulses. The damage tests for MDGs were
carried out with long pulse (12ns) in air and short pulse (0.66~9.7ps) in vacuum at 1053nm,
respectively. The experiment methodologies and results were discussed. For both long and short pulse,
the initial damage locates at the grating ridges opposite to the incoming wave, which is consistent with
the maximum normalized electric field intensity (NEFI). For long pulse, the damage is characterized by
melting and boiling. And for short pulse, the damage is ascribed to multiphoton-induced avalanche
ionization because of the electric field enhancement in the grating groove structure. And Measurement
results of the dependence of damage threshold on the pulse width are presented. And the damage
threshold of MDG in beam normal is 4.4J/cm<sup>2</sup> at 70° incidence angle for 9.7ps pulse.