title: Theoretical study of the spectroscopic and nonlinear optical properties of trans- and cis-4-hydroxyazobenzene.
abstract: We investigate the molecular structure, vibrational and electronic absorption spectra, and electronic hyperpolarizabilities of trans and cis isomers of 4-hydroxyazobenzene (HOAB) via density functional theory. Results show that the azo dye exhibits a high third-order nonlinear optical response and good optical transparency. Both the basis set and the functional are important influences on the results obtained when calculating the absorption spectrum and NLO response. We also study the effect of the solvent on the electronic absorption spectrum to assess the ability of the functional to reproduce the experimental spectrum in combination with a suitable solvent model. Our calculations show that the SMD model of Truhlar et al. handles the electrostatic and the non-electrostatic effects of hydrogen-bonding solvents on the absorption spectrum better than the traditional polarizable continuum model does. In addition, our results indicate that the dye trans-HOAB exhibits a high second hyperpolarizability and excellent optical transparency. Also, although the second hyperpolarizability of cis-HOAB is much lower than that of trans-HOAB, it is non-negligible when calculating the optical nonlinearity of HOAB under an optical pump. We also examine the effect of frequency dispersion on second harmonic generation. This study provides the basis for further research on the spectroscopic and nonlinear optical properties of novel azo dyes and other π-conjugated compounds.
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China. haipli@cumt.edu.cn.
authors.forename: Hai-Peng
authors.initials: HP
authors.lastname: Li
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Ze-Tong
authors.initials: ZT
authors.lastname: Bi
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Wen-Yue
authors.initials: WY
authors.lastname: Fu
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Run-Feng
authors.initials: RF
authors.lastname: Xu
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Xiao-Peng
authors.initials: XP
authors.lastname: Shen
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Ming-Xue
authors.initials: MX
authors.lastname: Li
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China.
authors.forename: Gang
authors.initials: G
authors.lastname: Tang
authors.affiliation: School of Physics, China University of Mining and Technology, Xuzhou, P.R. China. han6409@263.net.
authors.forename: Kui
authors.initials: K
authors.lastname: Han
keywords: Absorption spectrum; Azo dye; Density functional theory calculations; Frequency dispersion; Nonlinear optics; Solvent effect