Broadband antireflection coatings deposited with ion-assisted evaporation

SiO2, Ta2O5 and MgF2 have been deposited by electron beam evaporation under bombardment of ions generated by three different ion or plasma sources. Multilayer systems containing 5 to 12 layers have been designed and realized. The maximum reflectance R of a glass/air interface can be reduced down to R < 0.5 percent in a spectral region of 400 nm to 700 nm with each of such AR coatings mostly exceeds that of all-oxide system in the shorter wavelength region. With scanning scratch test the scratch resistance of the coatings have been determined relative to each other.