Pulse-width dependence of optical coating damages at 1053 nm laser wavelength is studied. Quarterwave-thick single layer films of high-index materials of A1203, ZrO2 and TiO2, and low-index materials of MgF2 and SiO2 were tested. Damage thresholds of the MgF2 and SiO2 films follow the square root dependence on the pulse-width T (VT scaling) over the pulse widths of 0.35-90 ns. Although the damage thresholds of the Al2O3, ZrO2 and TiO2 films followed the NA scaling from 0.35 to 1 ns, they become independent of the pulse-width for the pulse-widths longer than 6 ns. That is, the pulse-width dependence of the damage threshold is determined by the absorption property of the coating layer, which controls the damage mechanism.
K. Yoshida, K. Yoshida,
"Pulse-width dependence of optical coating damage at 1052 nm", Proc. SPIE 1438, Laser-Induced Damage in Optical Materials 1989, 143816 (1 November 1990); doi: 10.1117/12.2294451; https://doi.org/10.1117/12.2294451