Non-centrosymmetric alignment of an optically nonlinear dye

Multilayer Langmuir-Blodgett (LB) films of the organic dye, E-N-octadecyl-4-[2-(4-dibutylaminophenyl)ethenyl]pyridinium octadecylsulphate, are non-centrosymmetric. The second harmonic generation (SHG) increases quadratically with the number of layers and gives rise to a moderately high susceptibility of χ_zzz ⁽²⁾ 70 pm V^-1 at 1.064 μm. The real and imaginary parts of the dielectric permittivity at 532 nm and the LB layer thickness are ε_r=2.93 and ε_i=0.30 and l=3.70 nm, respectively