Modeling plasmonic efficiency enhancement in organic photovoltaics.

Efficiency enhancement of bulk heterojunction (BHJ) organic solar cells by means of the plasmonic effect is investigated by using finite-difference time-domain (FDTD) optical simulations combined with analytical modeling of exciton dissociation and charge transport efficiencies. The proposed method provides an improved analysis of the cell performance compared to previous FDTD studies. The results of the simulations predict an 11.

Ring-type plasmon resonance in metallic nanoshells.

A simple, approximate theoretical model of surface plasmon resonance in two-dimensional metal nanoshells is developed. The model is based on the concept of short-range surface plasmons propagating around closed circular metal nanotubes. In this model, the plasmon resonance in a metal nanotube is treated as a propagating, self-interfering plasmonic wave, in a ring-type resonance, at plasmonic wavelengths matching an integer fraction of the nanotube's effective circumference.

Light absorption enhancement in thin silicon film by embedded metallic nanoshells.

Computer simulation studies of absorption enhancement in a silicon (Si) substrate by nanoshell-related localized surface plasmon resonance (LSPR) based on a finite-difference time-domain analysis are presented. The results of these studies show significant enhancement of over 15x in the near-bandgap spectral region of Si, using 40 nm diameter, two-dimensional silver (Ag) nanoshells, simulating cylindrical nanoshell structure. The studies also indicate a clear advantage of the cylindrical nanoshell structure over that of a completely filled Ag-nanocylinders.

Experimental study of an ultrasmall pixel, one-dimensional liquid-crystal device.

A one-dimensional, ultrasmall pixel liquid-crystal (LC) device is experimentally demonstrated. The device has a one-dimensional array of ten 1 mm long, interdigitated, reflective gold electrodes on a glass substrate and a common transparent electrode on the opposite substrate. The interdigitated electrodes are 2 microm wide, separated by a 1 microm interelectrode gap.

The Image Transceiver Device: Studies of Improved Physical Design.

The Image Transceiver Device (ITD) design is based on combining LCOS micro-display, image processing tools and back illuminated APS imager in single CMOS chip [1]. The device is under development for Head-Mounted Display applications in augmented and virtual reality systems. The main issues with the present design are a high crosstalk of the backside imager and the need to shield the pixel circuitry from the photocharges generated in the silicon substrate.

Experimental study of phase-step broadening by fringing fields in a three-electrode liquid-crystal cell.

The fringing-field broadening of a phase-step profile and its dependence on the thickness of a liquid-crystal (LC) cell were studied in a simple, three-electrode LC cell structure consisting of two lateral electrodes biased with a differential voltage and a third, grounded, electrode placed on the opposite substrate. The results were compared both with an approximate analytical model developed earlier for a fringe-field-broadening kernel and with computer simulations. Good agreement between the experiment and the theoretical as well as the simulation results is shown.

Fringing-field effect in liquid-crystal beam-steering devices: an approximate analytical model.

An approximate analytical model was developed that links the fringing-field broadening of the phase profile of a liquid-crystal (LC) beam-steering device, and the resulting diffraction efficiency, to the physical parameters of the device including the cell thickness as well as the dielectric, optical, and geometrical constants of the device. The analysis includes a full solution of the Laplace equation for the LC device in which the broadening of the initial voltage profile into an effective voltage-drop profile, due to the fringing-field effect, is derived. It is shown that within the linear approximation used, the broadening of the phase profile is identical to the broadening of the effective voltage profile in the presence of the fringing field.

On the fringing-field effect in liquid-crystal beam-steering devices.

A detailed simulation of the fringing-field effect in liquid-crystal (LC)-based blazed-grating structures has been carried out. These studies are aimed at clarifying the relationship between the width of the fringing-field-broadened phase profile of the blazed grating and the LC cell thickness. This fringing-field broadening of the blazed grating's phase profile is shown to affect mostly the 2pi phase-step zone (fly-back zone) of the blazed grating.

High-resolution liquid-crystal-based spatial light modulator with a thin crystalline silicon photosubstrate structure.

We report an optically addressed, liquid-crystal-based spatial light modulator demonstrating a resolution of 25 line pairs/mm at 50% modulation transfer function and more than 40-line-pair/mm limiting resolution by using a 25-μm-thick silicon Schottky diode-array photosubstrate. This resolution is obtained concurrent with a high photosensitivity of approximately 20 μW/cm(2) and a contrast ratio of over 200:1. The high resolution and photosensitivity obtained with the thin photosubstrate are explained by a fringing field and an equivalent-circuit model, respectively.

Optically addressed spatial light modulator with a high photosensitivity and intensity adaptation range.

An optically addressed spatial light modulator based on a single-crystal silicon Schottky diode array photoreceptor and nematic liquid crystals with a high photosensitivity (better than 1microW/cm(2)) and input light intensity adaptation range (greater than 3 orders of magnitude) is demonstrated. This photosensitivity and intensity adaptation range is concurrent with a spatial resolution of 25 line pairsymm, contrast ratios greater than 200:1, and response times less than 10 ms in a wide photosensing wavelength range of 400-1100 nm.

Ternary phase and amplitude modulations using a twisted nematic liquid crystal spatial light modulator.

Ternary phase and amplitude modulations that use a reflective mode, 45° twisted nematic liquid-crystal spatial-light modulator are demonstrated. This use offers a simple method for implementation of ternary phase-amplitude filters with high resolution, high optical efficiency, and fast response time.

Application of a wire-grid-mirror liquid-crystal light valve in a nonlinear joint transform correlator.

We describe the operation of a wire-grid-mirror liquid-crystal light valve and its use for optical pattern recognition. The nonlinear characteristic of the wire-grid-mirror liquid-crystal light valve is used to implement the nonlinear joint transform correlator. Experimental results and computer simulations show that the nonlinear characteristic of the wire-grid-mirror liquid-crystal light valve can produce a well-defined correlation peak and low output background.

Introduction to the feature on spatial light modulators and their applications.

The special issue of Applied Optics on spatial light modulators presents a collection of papers that describe improvements in basic devices, smart pixels, and system applications.

Spatial light modulators for optical information processing: introduction by the feature editors.

Some twenty-five papers (including two Letters to the Editor) in this 15 November 1989 issue of Applied Optics consider the technology and use of spatial light modulators. This brief introduction reviews the field.

Near-infrared-to-visible image conversion using a Si liquid-crystal light valve.

A real-time near IR-to-visible image converter using a Hughes silicon liquid-crystal light valve (Si LCLV) has been demonstrated. A 1.06-microm image was converted to a 0.

Optimal operation temperature of liquid crystal modulators.

This paper describes analyses and confirming experiments on the optimum temperature for fast response in nematic liquid crystal (LC) modulators. It is demonstrated that the LCs or LC mixtures with higher nematic-isotropic phase transition temperatures have higher optimum temperatures and greater potential for improving the figure of merit. Also discussed is the performance of the LC mixture exhibiting optimum temperature at around room temperature.

Phase conjugation of low-power optical beans using liquid-crystal light valves.

A real-time hologram generated in the liquid-crystal layer of a leaky-mirror silicon light valve is read by the same low-intensity beams used to record it. For a particular geometry, one of the diffracted beams propagating away from the device is the optical phase conjugate of one of the original beams, thus permitting correction of path-propagation aberrations. Experimental results show correction of tilt, focusing error, and random phase aberrations.

Research on nonlinear optical materials: an assessment.

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986.

Pixel-by-pixel array division by optical computing.

An optical system, which divides two arrays in real time, has been conceived and demonstrated for the first time to our knowledge. The pixel-by-pixel division, performed with analog signals, treats two incoherently illuminated arrays in parallel. The configuration used is a feedback arrangement with the data introduced in the loop through two optical image converters (liquid-crystal light valves in our experiments).