2ND-HARMONIC GENERATION INVESTIGATION ON MOLECULAR-ORIENTATION IN LANGMUIR-BLODGETT-FILMS POLED BY AN ELECTRIC-FIELD

DC electric field induced molecular reorientation in hemicyanine Langm uir-Blodgett multilayers has been investigated by rotation-angle secon d harmonic generation (SHG) technique. The hemicyanine molecules could align their chromophore axes towards the field direction along the su bstrate normal, leading to reduction of the dipping-induced in-plane a nisotropy and enhancement of the macroscopic optical nonlinearity upon poling at room temperature. With increasing poling field, the SHG int ensity increased quadratically and reached an enhancement of an order of magnitude at a field of 1.33 x 10(6) V/m. (C) 1998 Elsevier Science B.V. All rights reserved.