PRACTICAL DESIGNS FOR THIN-FILM WAVE PLATES

Thin film wave plates are constructed by the oblique deposition of die lectric material onto glass substrates. Two basic designs incorporatin g biaxial columnar thin films have been proposed. The single-column-an gle plate provides different sensitivities of retardance to angular ti lting, but suffers from thickness (and hence retardance) wedging. The double-column-angle plate is relatively insensitive to tilt and substa ntially free of wedging. However, both basic designs are susceptible t o the ingress of atmospheric moisture, which has the effect of reducin g the retardance. In this paper we describe modifications to the basic designs that seal the wave plates against the uptake of atmospheric m oisture. The modifications eliminate wedging in the single-column-angl e plate, but the characteristic angular sensitivities of the basic des igns are retained. (C) 1998 Society of Photo Optical Instrumentation.