OPTIMIZING THE SEARCH FOR NEW FERRO-ELECTRIC/

FERROELASTIC OPTICS. S. C. Abrahams, Physics Department, Southern Oregon State College, Ashland, OR 97520, USA

The application of crystallographic principles to structural studies published in the literature provides an accelerated path toward new materials with desirable properties. Nonlinear optics differ from classical optics in having both a strong dependence on light intensity and a capacity for coherent light generation at combination frequencies. The impetus for increasing the number of known nonlinear optics arises from the demand for a range of devices dependent upon these unique properties, including second and third harmonic generation, parametric oscillation and optical bistability. Uses include high speed signal switching in all-optical systems and information storage at high densities. Nonlinear optic properties imply noncentrosymmetry. The magnitude of higher order optical susceptibilities is generally larger in ferroelectric crystals than in simple piezoelectrics and such materials are hence in greatest demand. The rate-determining step along the discovery path is the prediction of new ferroelectrics, or new ferroelectric/ferroelastics, using similar principles. Following verification of the predicted property additional criteria must be met, including transparency in the required spectral range, superior optic figures of merit and the growth of optical quality single crystals, before a material becomes a new nonlinear optic of value. Systematic application of established principles to all structures listed in several polar point groups within the inorganic database has led to the prediction of many new ferroelectrics; the eventual treatment of all polar point groups will substantially enlarge this number. In the meantime, new ferroelectrics have also been predicted from the current literature. Newly predicted ferroelectric/ferroelastic nonlinear optics will be discussed. This work has been supported by NSF grant DMR-9310461 .