Anisotropic second-order nonlinearities of organic monolayers.

Abstract

Monolayers prepared from hemicyanine chromophores of high second-order nonlinearity (\ensuremath{\beta}=1.3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}26}$ esu at resonance) have been used to study anisotropies of the concomitant ${\mathrm{\ensuremath{\chi}}}^{(2)}$-susceptibility tensor. All components of this third-rank tensor have been determined by Fourier analysis of the anisotropic coverage density ${\mathit{N}}_{\mathit{s}}$(\ensuremath{\varphi}) with respect to the angle of rotation about surface normal. Depending on the preparation both ${\mathit{C}}_{\mathit{s}}$ and ${\mathit{C}}_{2\mathit{v}}$ symmetry could be identified.