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

摘要

We investigated on cyanine dye (HQ) in Langmuir and Langmuir-Blodgett (LB) films using UV-visible spectra and second-harmonic generation (SHG) methods. UV-visible spectra indicated a uniform film transfer. The significant SHG fringe signal as a function of angle of incidence for Z-type LB films observed respectively. The second-order susceptibility χ~((2))_(zzz), refractive indexes at 532 nm as well as the average tilt angle ψ between the molecular (dipolar) axis and surface normal, obtained by means of fitting the SHG data, are 42 pM V~(-1), 1.4841, 57° and 32 pM V~(-1), 1.4775, 53° for LB films without and with Cd~(2+) ions, respectively. These high nonlinearities are due to resonant enhancement resulting from the proximity of the second harmonic wavelength to the absorption band of the films.