E. F. Aust

Light-induced orientation in a high glass transition temperature polyimide with polar azo dyes in the side chain

We report on both polar and nonpolar light-induced orientation of a polyimide of high glass transition temperature (Tg ≈ 210 °C) with nonlinear optical azo dye molecules in the side chain. This photoinduced orientation is shown to occur at room temperature, i.e., at least 190 °C below the Tg value of the polymer, which indicates that the photoisomerization-induced movement of the nonlinear optical chromophores induces, in turn, a movement of the polyimide main chain. This allows for an efficient orientation of the dye molecules in spite of the stiffness of the polyimide main chain. A nonpolar orientation is induced by polarized light irradiation alone, whereas polar orientation is achieved by application of a dc field during the photoisomerization process. Further light irradiation in the absence of a dc field destroys the previously induced stable polar order. A detailed theoretical study of this light-induced depoling process is also presented.

Electro‐optical waveguide microscopy

Optical waveguide microscopy is used to image lateral heterogeneities of the electro‐optic (EO) response of poled polymer waveguide structures. The sensitivity of the technique is demonstrated for a poly(methylmethacrylate) thin film doped with Disperse Red 1 between gold electrodes in a modified Kretschmann configuration. Even after aging of the poled polymer for one week, heterogeneities due to the anisotropy of the refractive index tensor can be distinguished from those owing to fluctuations of the EO coefficients.

GUIDED OPTICAL WAVES IN A FERROELECTRIC LIQUID CRYSTAL LAYER

This article reports on the use of guided optical waves for investigating ferroelectric liquid crystals. Although the liquid crystal layer is highly anisotropic in the SmA and SmC* phases, every principle value of the refractive index ellipsoid has been determined by choosing an appropriate rotation angle of the prism with respect to the direction of molecular orientation. In the SmC* phase, an alternating electric field gives rise to the molecular swing around the rubbing direction. The induced alternation of refractive indices provides a high contrast of reflectivity of the incident light, involving the particular characteristics of ferroelectric liquid crystals.

Electro-Optical Waveguide-Spectroscopy and -Microscopy

Abstract This paper deals with the application of some recently developed evanescent wave-optical techniques for the characterization of electro- optically active macromolecular systems. In particular, guided optical wave-spectroscopies and - microscopies are used to determine the linear and nonlinear optical properties.

Langmuir–Blodgett–Kuhn multilayer assemblies of NLO active amphiphiles and ionene polymers: Importance of complementary charges

Langmuir–Blodgett–Kuhn films of ionene polymers and nonlinear optically (NLO) active amphiphiles were investigated using several ultrathin film-sensitive techniques to determine multilayer ordering. Studies involved the formation of “passive–active” AB y-type multilayers of the ionenes and the NLO active amphiphiles. Deposition was possible with the use of an alternate three compartment dipping trough. The multilayer structures and thicknesses were verified by X-ray diffraction and reflection measurements and surface plasmon spectroscopy on a gold-coated glass substrate. Two main factors were determined to be responsible for the formation of stable alternating film architectures, namely electrostatic interaction in the hydrophilic layers and the van der Waals interaction in the hydrophobic layers. The use of ionenes as a class of amphiphilic polymers allowed the preparation of films with excellent optical quality.

Evaporated polyurea optical waveguides: electrooptic and structural properties

Abstract Electrooptically active planar waveguides of aromatic polyurea were prepared by simultaneous deposition of 4,4′-diamino-diphenyl-methane and 4,4′-diphenylmethane-diisocyanate from the vapor phase and subsequent corona poling. X-ray diffraction spectra show that part of the films has a pronounced layered structure reminiscent of self-assembling systems. Attenuated total reflectance spectroscopy of the waveguide modes of the polymer films was used to measure the piezoelectric and electrooptic susceptibilities. The contributions of the nonlinear polarizability of the urea groups and their dipolar orientation in the applied field are identified. Possible applications of this material for novel optical modulator geometries are discussed.

Novel polymeric materials, architectures, and characterization techniques for electro-optics

Abstract This contribution deals with recent developments in the field of integrated electro-optics. We first present a novel characterization technique based on optical waveguide microscopy that allows for the imaging of linear and nonlinear optical lateral heterogeneities in planar waveguide structures. Next, a new class of amorphous polymers is introduced: the charged groups of solid polyelectrolytes are compensated by counter-ions with a high χ(2) response. The advantage of these materials is their high level of doping that can be achieved without recrystallization observed for other host/ guest-systems. And finally, we present waveguide structures based on the Langmuir/ Blodgett/ Kuhn-technique with a complex internal optical architecture controlled at the molecular level.