Organic nonlinear optical crystals based on configurationally locked polyene for melt growth

A series of nonlinear optical chromophores based on configurationally locked polyene are synthesized, and the single crystal growth from the melt are investigated. The chromophores consist of a pi-conjugated hexatriene bridge between the dialkylamino or methoxy electron donors and the dicyanomethylidene electron acceptor. The physical and nonlinear optical properties and the single crystal X-ray structures of these chromophores are characterized. Specifically, the chromophore 2-{3-[2-(4-dimethylaminophenyl)vinyl]- 5,5-dimethylcyclohex-2-enylidene} malononitrile (DAT2) exhibits a strong powder second-harmonic generation signal of about 2 orders of magnitude greater than that of urea and a large temperature difference of 80 degrees C between the melting temperature and the recrystallization temperature. Finally, we demonstrate the growth of single crystalline thin films of DAT2 by a Bridgman-type melt growth technique, which gives a new direction for organic nonlinear optical crystal engineering using melt-growth techniques.