Optical properties of thin films as short pulse laser debris shields

The debris mitigation is a major challenge for all high-peak-power lasers system. Costly, long lead time focusing parabolas need to be protected from target debris. In order to solve the problem, we employed some preliminary research. In this work, the optical properties of three kinds of thin films (fluorinated ethylene propylene (FEP), perfluoroalkoxy copolymer (PFA) and ethane-tetrafluoroethylene copolymer (ETFE)) were investigated with respect to their application as laser debris shields. The results indicate the transmittance of FEP film at 355 nm is the highest in that of the three films reaching about 93%, though the three thin films all present good transmittance. Thus, the transmittance wavefront and the laser induced damage of FEP film were further investigated. The result indicates that the wavefront error of FEP film is about 1.06 . The damage test was performed with a 355 nm neodymium: Yttrium aluminum garnet (Nd:YAG) laser with a 9.3 ns pulse duration, and it is found that the highest non-damage fluence for FEP film is 10.35 J/cm2 and the 100% damage fluence is 11.48 J/cm2.