Electrochromism in absorbing optically second-order nonlinear media

We show the results of investigations of the linear electroabsorption in a second-order optically nonlinear medium. The spectral behavior of the effect is determined by the dispersion of the imaginary part of the second order susceptibility, χ⁽²⁾(-ω;ω,0). Experimentally, we performed spectral measurements of both the dispersion of the complex linear electro-optic coefficient and the electroabsorption in poly[vinylcarbazole] doped with a second order active molecule, 4-(N,N-diethylamino)-β-nitrostyrene, in the range from 400 to 700 nm. The induced absorption is linear in the applied field and exhibits a single peak at 560 nm that coincides with the wavelength at which the imaginary part of electro-optic coefficient exhibits maximum. This peak is distinctly shifted from the maximum of the linear absorption band of the films, observed at 470 nm.