Abstract

Uncoated electrooptic and photorefractive materials such as LiNbO₃, BaTiO₃, CdTe, and PLZT all exhibit large first surface reflectivities (~20%) due to their high refractive indices (n ~ 2.2-2.6). Therefore, photorefractive recording in volume holographic applications suffers from reduced optical throughput (~64%) as well as problematic multiple reflections that tend to reduce the grating modulation while recording extraneous gratings. This situation is further aggravated by the necessity to operate photorefractive devices over a broad range of wavelengths, polarizations and input angles, often simultaneously. An effective bandpass antireflection (AR) coating previously developed for bismuth silicon oxide (Bi₁₂SiO₂₀) consisting of an electron-beam deposited double layer quarterwave stack of magnesium fluoride and zirconium dioxide has been modified to apply to the specific substrate indices and operating wavelengths of the photorefractive materials listed above. The as-deposited AR coatings exhibit desirable broadband characteristics with reflectivities well below 1%. In addition, measured reflectivities were shown to be relatively insensitive to both polarization (TE, TM) and angles of incidence over the 0-45° range.

© 1989 Optical Society of America