SYNTHESES OF ORGANIC NONLINEAR OPTICAL-MATERIALS

There is currently extensive interest in the nonlinear optical (NLO) properties of organic compounds. Especially, the large second or third order NLO responses of materials are important in the fields of optical device technology. This paper reviews the syntheses of organic NLO compounds to correlate the NLO responses with chemical structures. Molecular design by means of MO method and crystal engineering of NLO compounds are described in details. Nitroaniline and cyanostyryl derivatives with intramolecular charge-transfer chromophores have excellent NLO characteristics for second order NLO materials. On the other hand, large pi-conjugated compounds, such as phthalocyanines, azo and azomethine dyes as well as pi-conjugated polymers such as polydiacetylenes, polyphenylenevinylenes and polythiophenes are expected to have good third order NLO responses for opto-electronics devices.