Nodular defects induced laser damage of 532 nm thin-film polarizers

Abstract

The laser damage characteristics of the thin-film polarizers for the wavelength of 532 nm and AOI of 56° were investigated using a Nd:YAG laser system with a wavelength of 532 nm and a pulse width of 9 ns. The results showed that the damage morphologies induced by nodular defects in the witnesses is significantly different compared to 1064 nm polarizers. The nodular seeds are incompletely ejected after on-shot laser and butterfly-like damage pits are formed, which gradually develop into the typical nodular ejection pits as laser irradiation. Analysis of the internal structure showed that single or two adjacent SiO2 particles formed the nodular seeds, which were mainly located in bottom layers and were tightly bound to the surrounding layers. In addition, the simulated electric field intensity (EFI) distributions and damage morphologies of nodular defects with different structures were compared, and it was found that the formation of the nodular damage is closely related with the EFI distributions in the thin films.