Z-type Langmuir-Blodgett films of a three-component optically nonlinear dye

Langmuir-Blodgett (LB) films of N-octadecyl-4-[(4-dimethylaminophenyl)azo]p yridinium iodide are Y-type and consequently the second-harmonic intensity is modest when the number of layers is odd and negligible when even. Howeve r, the required non-centrosymmetric structural arrangement may be obtained by combining the cationic dye in a 1:1:1 ratio with an amphiphilic ammonium cation and a complex dianion; the second-harmonic intensity from LB films of [N-octadecyl-4-[(4-dimethylaminophenyl)azo]pyridinium](+)[dioctadecyldim ethylammonium](+)[bis(2-thione-1,3-dithiol-4,5-dimercapto)zinc](2-) then in creases as I-2 omega(N) = I2 omega(1)N2, where N is the number of layers. T he films have an effective second-order susceptibility of chi(eff)((2)) = 1 0 pm V-1 at 1.064 mu m. (C) 1999 Elsevier Science B.V. All rights reserved.