Jay S. Schildkraut

Determination of the electrooptic coefficient of a poled polymer film

The use of the rate of change of the relative phase shift of p- and s-polarized light with voltage to determine the electrooptic coefficient of a poled polymer film is discussed.

Theory and simulation of the formation and erasure of space‐charge gratings in photoconductive polymers

Equations that describe the formation of space charge in a photoconducting polymer are presented. The equations are written in a nondimensional form that includes the electric‐field dependence of charge generation efficiency, charge mobility, recombination rate, and trapping rate. The equations are solved numerically for the condition of illumination with an intensity distribution that varies sinusoidally with position. The effect of traps on the formation of a space‐charge grating is modeled. Finally, the erasure of the space‐charge grating by uniform illumination is considered.

Absorption and second-harmonic generation of monomer and aggregate hemicyanine dye in Langmuir–Blodgett films

Absorption spectra and second-harmonic generation of Langmuir–Blodgett monolayers containing a hemicyanine dye with a large second-order hyperpolarizability are reported. The dye is found to be in the form of H aggregates in a pure-dye film and mostly monomeric in a 1:4 dye–arachidic acid film. This observation explains a report in the literature that mixed dye–arachidic acid films display greater second-harmonic generation efficiency than a pure-dye film. It may also be a factor in the reported failure of second-harmonic generation to increase quadratically with the number of layers in noncentrosymmetric multilayer films.

PHOTOCONDUCTING ELECTRO-OPTIC POLYMER FILMS

We describe electro‐optic polymer films that also exhibit photoconductivity. An acrylic polymer containing (as a side chain) a stilbene chromophore with a high second‐order nonlinear susceptibility was doped with a perylene sensitizer for photocharge generation and a triarylamine hole transporting molecule. A polymer film was fabricated that had an electro‐optic coefficient of 2.5 pm/V. Absorption of light by the sensitizer, that occurs in a region in which the polymer is otherwise transparent, results in a photocurrent and charge trapping. The quantum efficiency of photocharge generation and photorefractive figures of merit were calculated.

Photorefractive effect in a new organic system of doped nonlinear polymer

We report an experimental observation of the photorefractive effect in a new polymeric system in which a nonlinear organic polymer was doped with a photosensitizer, borondiketonate (BDK), and a hole transport agent, tri‐p‐tolylamine (TTA). The photoconductivity and the electro‐optic effect have been studied. The process of grating formation with the applied field is presented. A strong electric field dependence of the diffraction coefficient has been observed.

Long-range surface plasmon electrooptic modulator

An electrooptic modulator based on electrically varying the degree of coupling of a light beam to a long-range surface plasmon excitation is modeled. A specific embodiment of a modulator is shown to be capable of changing its reflectance from 0.00 to 0.84 on the application of 100 V across a 1-microm thick electrooptic film with a second-order susceptibility of 2 x 10(-7) esu. The affect that the width of the long-range surface plasmon excitation resonance has on the performance of the modulator is considered. Plane-wave calculations show that decreasing the width of the resonance increases the amount of modulation possible for a given voltage change. More realistic calculations which take into account diffraction of a beam of finite width show that a decrease in resonance width can in some cases degrade device performance.

Methods for generating blue-noise dither matrices for digital halftoning

Blue-noise dither halftoning methods have been found to produce images with pleasing visual characteristics. Results similar to those generated with error-diffusion algorithms can be obtained using an image processing algorithm that is computationally much simpler to implement. The various techniques that have been used to design blue-noise dither matrices are reviewed and compared. In particular, a series of visual cost function based methods and several techniques that involve designing the dither matrices by analyzing the spatial dot distribution are discussed. Ways to extend the basic blue-noise dither techniques to multilevel and color output devices are also described, including recent advances in the design of jointly optimized color blue-noise dither matrices.

Zero‐order and first‐order theory of the formation of space‐charge gratings in photoconductive polymers

When a photoconducting polymer is illuminated by light with an intensity that varies sinusoidally with position, the space‐charge electric field, hole density, ionized photosensitizer density, hole trap density, and other properties, will also vary with position. We derive an expression for the zero‐order Fourier component of the hole density and a linear system of equations for the first‐order Fourier component of a number of variables. The system of equations is solved for the steady‐state first‐order Fourier component of the electric field for the case in which hole untrapping is negligible or no hole traps are present. Next, the equations are simplified for the case in which the initial trap density is far greater than the density of holes, and for the case of no hole traps. Finally, we compare the zero‐order hole density and first‐order electric field calculated from our equations to values obtained by Fourier transforming the results of numerical calculations.

A fully automatic redeye detection and correction algorithm

A fully automatic redeye detection and correction algorithm was developed at Eastman Kodak Company Research Laboratories. The algorithm is highly sophisticated so that it is able to distinguish most redeye pairs from scene content. It is also highly optimized for execution speed and memory usage enabling it to be included in a variety of products. Detected redeyes are corrected so that the red color is removed, but the eye maintains a natural look.

Dispersion of the complex electro-optic coefficient and electrochromic effects in poled polymer films

The importance of electrochromic effects in the ellipsometric determination of the electro-optic coefficient of poled polymer films is discussed. A relation between electrochromism and the complex electro-optic coefficient is proposed. The dispersion of the electro-optic coefficient for the charge-transfer molecules is shown to follow the simple two-level model.