Second-Order Hyperpolarizabilities of Aromatic Carboxylates without Visible Absorption

Abstract

The second-order hyperpolarizabilities (β) of aromatic carboxylates were evaluated by the hyper Rayleigh scattering method at 1.064 µ m and semiempirical molecular orbital calculation. The β values of methyl methoxybenzoate and its dimer in methanol solution were measured to be 22 and 49×10 -30 esu, respectively, which are about 0.6 and 1.3 times that of p -nitroaniline. The calculation of β and dipole moment (µ ) of the methyl methoxybenzoate oligomers revealed an almost linear increase of these values with increasing number of repeating units up to trimers. Since the oligomers have a short cutoff wavelength of about 300 nm as well as large β and µ, these compounds are concluded to be promising chromophores for second-order nonlinear optics.