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

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2008-05, Vol.321 (1), p.7-10
• Main Authors: Gao, Feng, Wang, Chuang, Zeng, Hao, Ma, Shihong
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Cyanine dye; Exact sciences and technology; General and physical chemistry; Langmuir blodgett films; Langmuir–Blodgett film; Second-harmonic generation (SHG); Surface physical chemistry; UV–vis spectra
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2008.02.017

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 nm and average tilt angle ψ between the molecular (dipolar) axis and surface normal from fitted SHG data are 1.4841, 57° and 1.4775, 53° without and with Cd 2+ ions, respectively. The second-order susceptibility χ ZZZ ( 2 ) = 42   pm   V − 1 and 32 pm V −1 for LB films with and without Cd 2+ 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.