Second-order nonlinear optical properties of unpoled bent molecules in powder and in vacuum-deposited film

The second-order nonlinear optical (NLO) properties of the monolithic bent molecule (Cz-Oxd(2)), two oxadiazolylstyryl moieties bridged to a carbazole . have been investigated for powder and film forms. The powdered sample was studied by using second harmonic generation with a total reflection geomet ry, and the effective NLO coefficient of Cz-Oxd(2) in powder form was measu red to be 1.2 pm/V at a fundamental wavelength of 1.36 mum. In the ultrathi n film prepared by using the vacuum deposition method, a bent molecule was found to have a tendency to be aligned parallel on the surface of a solid s ubstrate.