Linear and nonlinear optical properties in Langmuir-Blodgett multilayers of new cyanine dye

We investigated on cyanine dye (HQ) in Langmuir and Langmuir-Blodgett (LB) films by UV-vis spectra and second-harmonic generation (SHG) methods. UV-vis spectra indicated a uniform film transfer. The significant SHG fringe signal as a function of angle of incidence for Z-type LB films was observed respectively. The refractive indexes at 532 mn and average tilt angle psi between the molecular (dipolar) axis and surface normal from fitted SHG data are 1.4841, 57 degrees, and 1.4775, 53 degrees without and with Cd2+ ions, respectively. The second-order susceptibility X-ZZZ((2)) = 42 pmV(-1) and 32 pmV(-1) for LB films with and without Cd2+ ions are obtained by measuring SHG signals. These high nonlinearities are due to resonant enhancement resulting from the proximity of the second-harmonic wavelength to the absorption band of the films. (C) 2008 Elsevier B.V. All rights reserved.