Multichannel laser-induced contamination test bench

Kurzfassung

Lifetime enhancement of optical components is still one of the major topics in space based laser applications. In this paper a novel multichannel test setup for basic research of laser- induced contamination (LIC) phenomena is introduced. Main part of the setup is an ultra-high vacuum chamber with a contamination source similar to a Knudsen cell, which offers the possibility to apply constant partial pressure of pure contamination material throughout the whole time of testing. Up to three different optical samples can be tested simultaneously under identical experimental conditions. As laser source a diode pumped Nd:YAG system with frequency doubling and tripling is used. It provides 10 ns pulses with a repetition rate between 1 and 1000 Hz and 2.5 mJ pulse energy for 355 nm. Contamination growth is monitored online by transmission and fluorescence detection. LIC growth dynamic was analysed in dependence on laser fluence and repetition rate. Uncoated and HR and AR coated fused silica optics were investigated. The coatings were produced by different processes: e-beam, Ion Beam Sputtering, and Magnetron Sputtering. The influence of coating morphology and composition on LIC growth is discussed.