Ion Beam Applications For Optical Coating

Ion beam techniques can be applied advantageously during different phases of optical coatings. Prior to deposition, substrates can be ion beam cleaned with rare gas or reactive gas ions, depending upon the substrate materials involved. During deposition, ion beam sputtering can be employed to produce films of superior optical and mechanical qualities. A hybrid technique has been demonstrated in which coating material initially is sputtered by the ion beam, and subsequently it is generated thermally due to target heating by the ion beam. In this way advantages of sputter deposition are realized during initial stages of film growth, and faster deposition rates can then be achieved using thermal generation. Another hybrid deposition technique involves ion bombardment of the optical surface while simultaneous condensation of thermally generated dielectric material occurs. Potential advantages of this technique include controlled changes of physical and chemical characteristics of the film.