Effect of dual-pulse temporal shaping on ultraviolet nanosecond laser damage of fused silica surface in high fluence regime

The pre-pulse and post-pulse have the opposite effects on the damage behaviors at pulse delay of 20 ns. The pre-pulse irradiation significantly increases the main-pulse threshold to be much higher than the single-pulse threshold, but the post-pulse has little effect on the main-pulse threshold.

For near-threshold damage sites, the pre-pulse reduces the average damage size and depth to be smaller than those of single-pulse, while the post-pulse drastically increases the average size and depth to be much larger than single-pulse. The average size of the damage site is monotonously increased from 43.6 µm to 127.9 µm with raising the post-pulse energy. For the pre-pulse case with the shape factor of 0.61, the damage threshold of main-pulse increases with the delay and nearly stabilizes after 10 ns.