Highly polar molecular crystals for electro-optic applications

We report on a series of new acentric 4-nitrophenylhydrazone derivatives which bear more than one hydroxy or methoxy electron donating group whose large molecular nonlinear optical properties were characterized with semi-empirical calculations and hyper-Rayleigh scattering. The second harmonic powder test results of several compounds showed large signals, two to three orders of magnitude larger than urea, which make these materials potentially interesting for nonlinear optics. Crystals of one of these hew molecules (3,4-dihydroxybenzaldehyde-4-nitrophenylhydrazone, 3,4-DHNPH) are very promising for electro-optics. The properties are discussed in detail and a comparison with some of the best existing crystals for electro-optic applications is given.