Abstract

Soon after the first demonstration of the orientation analysis based upon the evaluation of nonlinear optical signals obtained by second-harmonic generation (SHG) the orientation behavior of liquid-crystal (LC) thin films has gained increasing scientific interest, revealing the mechanisms of bulk and surface LC-alignment via interaction between substrate surface, surfactant, and organic thin film. The perfect in-plane alignment of LC-layers and other selected organic molecules, which exhibit a strong tendency for polar ordering, is an excellent example of rotational anisotropy. In fact, organic monolayers usually show rotational isotropy around the surface normal. We have measured the anisotropic orientation behavior of LC-films. A high degree of inplane anisotropy was obtained by depositing the LC-films onto rubbed polyimide-covered substrates. The analysis with respect to the relevant second-order susceptibility tensor components is based upon the experimental results obtained in total reflection geometry and transmission geometry which allowed a stepwise increase of the angle-of-incidence β (Fig. 1).

© 1992 IQEC