Application of ionized cluster beam to anti-reflection coating of transmission windows

High transmission films with high adhesive strength have been developed by using the ionized cluster beam (ICB) method. It was demonstrated that the acceleration voltage plays a very important role in controlling the optical quality of films. The transmission windows obtained are as follows. (1) The germanium (Ge) window coated with a zinc sulfide (ZnS) film obtained at 3 kV acceleration voltage had a transmittance of 96% at 10 μm wavelength and the adhesive strength of the film obtained was over 430 kg cm-2, which endured even after thermal treatment at 4600C. (2) The zinc sulfide (ZnS) window coated with lead fluoride (PbF2) film obtained by controlling the acceleration voltage within the range from 0.5 kV to zero had a transmittance of 95% at 10 μm wavelength and the adhesive strength of the film was 240 kg cm-2. (author)