Novel third-order nonlinear optical materials composed of ionic polymers and chromophores

The complex composed of ionic polymer and ionic dye was investigated for third order nonlinear optics. The complexes were prepared by ion exchange reaction between sulfonic group of the polymers and cationic dyes. As cationic dyes, hemicyanines(HC-n), where n indicates the number of double bonds between the aromatic rings, oxacyanine(OC-1) and triphenylmethane derivatives were used. The dye content of the complex could be controlled with in the range of 0.1-0.6 molar ratio of bound dyes to the sulfonic groups by the composition of mixed solvents for the reaction. The thin films of complexes were made by spin coating of their CHC13/MeOH solution on fused quartz plates. They were transparent and homogeneous with naked eyes and polarizing microscope. THG measurements were performed by use of pumping laser light from 1.5im to 2.ljim. x3 values of every complexes were found to be linearly proportional to the dye content (M)(mmol/cm3). The x3 values of hemicyanine complexes became large at the pumping wavelengths in resonant region of every dyes, and x3 of HC-2 was always larger than that of HC-1, whereas that of OC-1 with a srnmetrical structure was ten times smaller than that of HC-1. The largest values attained at each maximum (M) and at the pumping of 1.5m were 1.8x10"esu for HC-1, 2.4x10"esu for HC-2 and 1.7x10"esu for Crystal Violet. However, in the case of Malachite Green and Basic Cyanine 6GH, their THG intensities were negligibly small even at resonant region.