Abstract

The benefits of ion based deposition processes such as ion assisted deposition (IAD), plasma ion-assisted deposition (PIAD), reactive ion plating (RIP), magnetron sputtering and ion beam sputtering have been described in the literature for two decades. One important paper was given by Martin and Netterfield in 1986 [1]. The ability to produce oxide films with high packing density is common for these deposition techniques. The temperature stability of optical coatings, defined by the temperature dependence of the optical performance, depends strongly on the packing density of the individual layers in a multilayer stack. If the film structure is not fully dense, water vapor from the air can penetrate the film. In that case the average refractive index varies with air humidity and ambient temperature. This leads to an vacuum to air shift which is typical for conventional evaporated oxide coatings. The vacuum to air shift of the optical thickness is in the range between 1% to 5 % [1,2,3]. With high packing density films there is no discernible difference between the spectral photometric measurements in vacuum and on air [1,2,3].

© 1998 Optical Society of America