Linear optical properties of the nonlinear optical calcium and strontium tartrato-antimonates (III), Ca[Sb2{(+)-C4H2O6}2] •2H2O and Sr[Sb2{(+)-C4H2O6}2] •2H2O

The study of nonlinear optical properties of crystals requires a thorough knowledge of the linear optical properties: knowledge of the transparency range is necessary, some information about the optical activity is useful. Above all, high quality refractive indices (with errors less than 10(-4)) and their dispersion are the most important basic data, as they enable a detailed analysis of phase-matching conditions of nonlinear optical processes and an estimation of the nonlinear optical potential of a new non-centrosymmetric crystal. Such high quality refractive indices are also necessary in other areas of nonlinear optics, for example for the evaluation of nonlinear optical measurements like measurements of Maker fringes. In this short communication we present the linear optical basis for nonlinear optical investigations of the hexagonal calcium and strontium tartrato-antimonates, Ca[Sb-2{(+)-C4H2O6}(2)]. 2H(2)O ("CaSbT") and Sr[Sb-2{(+)-C4H2O6}(2)]. 2H(2)O ("SrSbT"). The Sr compound has been known for a long time; its morphological crystallography is already presented in the famous Chemische Krystallographie by Paul Groth (1910). The Ca salt was first synthesized 1983 by one of us (L.B.).