Optimal coating solution for a compact resonating cavity working at Brewster angle.

In a compact Nd:Glass resonator, the laser that enters the gain medium at Brewster angle can work either for P-polarization or S-polarization, in which polarization the optical coatings possess higher laser-induced damage threshold (LIDT) was investigated. For the P-polarized configuration, only one high reflection (HR) coating on the rear surface of the Nd:Glass substrate is needed, and the laser-induced damage occurred near the substrate-coating interface at a fluence of 10 ± 2 J/cm² (1064nm 10ns). Although S-polarized configuration needs two coatings, one HR coating and one anti-reflection (AR) coating on the rear and front surface of the Nd:Glass substrate respectively, its overall LIDT was about 1.8 times higher than that of the P-polarized configuration. The laser-induced damage occurred at the interface between the S-polarized AR coating and the Nd:Glass substrate. The observed interfacial damage behaviors were interpreted using a phenomenological model that took the nano-sized absorbers, electric-field intensity (EFI) distribution and coating thickness into consideration.