ORGANIC MOLECULAR-CRYSTALS FOR OPTICAL-DATA PROCESSING

We report on the nonlinear optical properties of a new class of organi c compounds built of trihalides interacting weakly with donor type mol ecules. The adducts of iodoform with sulphur (CHI3.3S8) and iodoform w ith quinoline (CHI3.3C9H7N) exhibit sizeable electrooptic effects and second harmonic generation comparable to those of the most efficient o rganic coumpounds such as MNA (methylnitroaniline). For both iodoform compounds the angle-tuned phase matching of type I and II has been obs erved. The comparison between the electrooptic effect and the second h armonic generation suggests that in these materials the electrooptic e ffect is mostly electronic in origin. This permits the construction of high speed electrooptical modulators and switching devices operating at very high frequencies up to the terahertz region. The macroscopic o ptical nonlinearity of the adducts stems mainly from the nonlinearity of the iodoform molecule. The largest electrooptic coefficients (r22 = 2.2pm/V) and the largest nonlinear optical susceptibility (d22 = 19.1 pm/V) were measured in the iodoform-sulphur compound.