Organic molecular materials displaying effective optical second harmonic generation (SHG) is of major interest in molecular engineering and non-linear optics. In this review synopsis of experimental and theoretical studies of photoactive molecular multilayer Langmuir-Blodgett (LB) films of oriented dipolar betaine type organic molecules is presented and the pathways of search of new indandione-1,3, pyridinium betaine (IPB) derivatives with enhanced second- order non-linear response are discussed. Characterization of highly dipolar betaine-type molecules, with IPB molecule as a prototype, has been presented and conditions of effective SH generation discussed. Molecular structure, phase transitions and optical properties of monolayers of amphiphilic IPB derivatives on the water/air interface have been discussed. Electronic and both linear and non-linear optical properties of LB multilayer molecular assemblies of amphiphilic IPB derivatives have been discussed. New developments in molecular engineering in search for new molecular compounds with high SHG response have also been briefly discussed.
Edgar A. Silinsh,
"Organic molecular materials for nonlinear optics", Proc. SPIE 2968, Optical Organic and Semiconductor Inorganic Materials, (6 February 1997); doi: 10.1117/12.266807; https://doi.org/10.1117/12.266807