Experimental Characterization of Novel Materials for Nonlinear Optics Represented by Iodoform Complexes

We report on nonlinear optical properties of a new class of efficient nonlinear optical compounds built of trihalides interacting weakly with donor type molecules. Adducts of iodoform with sulphur (CHI 3 · 3S 8 ) and quinoline (CHI 3 · 3C 9 H 7 N) exhibit sizeable electrooptic effects and second harmonic generation comparable to POM and better than urea. Angle-tuned phase matching of type I and II has been observed for both compounds. The comparison between the electrooptic effect and the second harmonic generation suggests that the electrooptic effect is mostly electronic in origin. The atomic force microscope was used to record the molecular structure on free-standing iodoform-sulphur crystal plates. The intermolecular spacings on the crystal surface correspond remarkably closely with those in the bulk.