Enhancement of Electrooptic Effects at Wavelengths in the Proximity of Electronic Resonances

Abstract

The notion is analyzed of obtaining materials with large electrooptic coefficients relative to their dielectric constants by incorporating appropriate optical transitions near the operating wavelengths. It is shown that in such cases the absorption coefficient becomes an important practical parameter of the material. Enhancement of the electrooptic effect in the vicinity of an optical transition was indeed observed in the compound Na3Li(CrO4)2 · 6H2O. The electrooptic coefficient n03r22 was found to be 9.7 × 10−8 cm/statV at ν˜ = 1.67 × 104 cm−1 and 12.2 × 10−8 cm/statV at ν˜ = 2.00 × 104 cm−1. The absorption coefficient on the tail of the t1 → e transition of the chromate ion was considerably greater than what was initially estimated. This was shown to be due partially to the effects of lattice vibrations and partially to crystal imperfections. The extra absorption can in principle be eliminated, and it is concluded that the approach investigated could lead to electrooptic materials with improved characteristics.