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-Ocursive Greek chid₂), 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 geometry, and the effective NLO coefficient of Cz - Ocursive Greek chid₂ in powder form was measured to be 1.2 pm/V at a fundamental wavelength of 1.36 μm. In the ultrathin 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 substrate.