Abstract

Communications through the 440-470nm water transmission window requires a laser, a narrow band high field of view filter, and an appropriate detector. Polarization interference filters offer very narrow transmission bands, wide angular field of view, and tuning capability. The Lyot-Ohman, Solc, various hybrids, and recent designs are powerful examples of technologies employing common single crystals of quartz, calcite, or ADP. The superior iso-index filter (n_o = n_e at a particular λ) is potentially the most useful. Materials for iso-index filters are not common since they must be stable single crystals, high quality, and usually involve mixed ions in an isomorphous structure. The research group at UCLA has shown that β"-Al₂O₃ fulfills these conditions within the Na-Ag system . However, β"-Al₂O₃ does not melt congruently and large single crystals are not attainable readily. An alternate superionic conductor, β-Al₂0₃, behaves similarly and can be grown as sizeable (1 × 6 inch) boules.

© 1992 Optical Society of America