Merocyanines nonlinear materials

The large molecular hyperpolarizability of the merocyanine chromophore (4,5) and the highly polar environment of the quasicrystals has prompted studies of the second order nonlinear optical properties of these materials (6). 

To illustrate the potential of LB films in nonlinear optics, two examples will be given to illustrate both quadratic- and cubic-order effects. The motivation for the first example came from early accounts of nonlinearity in a specific merocyanine dye molecule (49). No good crystals of this material are available, but an extremely large value of P was predicted on the basis of measurements with powdered samples. The reliability of such data is not high because powder efiSciency is a function of particle size distributions. The initial experiments were with a simple merocyanine dye alternated with o)-TA. However, the best results (50) were obtained by using organic superlattices based on the two molecules shown by Structures 4. la and 4. lb. 

Okada, S., Masaki, A., Matsuda, H., Nakanishi, H., Koike, T., Ohmi, T., Yoshikawa, N., and Umegaki, S., Merocyanine-p-toluenesulfonic acid complex with large second order nonlinearity, in Nonlinear Optical Properties of Organic Materials III (Proc. SPIE, 1337), Khanarian,... 

Ferroelectric behavior has been detected for polymer 11, as a consequence of the "chiral smectic-C" stracture of the liquid crystalline phase (29). Polymer 12 is a second order nonlinear optical material, the polarizable side groups, in which can be poled in a 10-20 kV electric field to generate values in the region on 34-45 picometers per volt (30, 31), Finally, species 13 is a photochromic polymer, which undergoes a spiropyran-merocyanine transformation when exposed to ultraviolet light (32),... 

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