Volume 89, Issue 11, 01 June 2001
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
Analysis of the scattered light distribution of a tightly focused laser beam by a particle near a substrate89(2001); http://dx.doi.org/10.1063/1.1365941View Description Hide Description
We present a calculation method to analyze the scatteredelectromagnetic field by a particle near a substrate. The method is based on the iterative calculations of the extended Mie scatteringtheory [J. P. Barton, D. R. Alexander, and S. A. Schaub, J. Appl. Phys. 64, 1632 (1988)] and of plane-wave decompositions in order to include the multi-scattering between the particle and the substrate. The method is applicable to an arbitrary incident beam and an arbitrary distance between the particle and the substrate. It is possible to analyze the interaction between a particle and a multilayered substrate. We present the electromagnetic field distribution when the particle near the substrate is illuminated with focused laser beam.
89(2001); http://dx.doi.org/10.1063/1.1367314View Description Hide Description
Resonance of space-charge field can occur in photorefractive polymers through a moving fringe and can be described by a forced oscillation equation with damping. The resonance frequency and the magnitudes of both the amplitude and the imaginary part of the space-charge field at the resonance frequency are functions of three experimental parameters: total incident intensity, applied electric field, and grating wave vector. Thus, the diffraction efficiency of grating and the gain coefficient of two-wave mixing are dependent on the three experimental parameters. Our theory can also be applied to inorganic photorefractive crystals.
89(2001); http://dx.doi.org/10.1063/1.1370364View Description Hide Description
We fabricate semi-insulating InGaAs/GaAs multiple quantum wells and observe the excitonic enhancement of the photorefractivity in the Franz–Keldysh geometry at wavelengths of 0.92–0.94 μm. A maximum two-wave mixing gain of 138 and a maximum diffraction efficiency of are obtained. The saturation intensity and the spatial resolution are also measured by four-wave mixing. The diffraction efficiency is saturated at a high external electric field. The dominant cause of this saturation is the deviation of the excitonic electroabsorption from its quadratic law.
Determination of the emission zone in a single-layer polymer light-emitting diode through optical measurements89(2001); http://dx.doi.org/10.1063/1.1350998View Description Hide Description
We study the emission zone in a single-layer polymer light-emitting diode. The emission zone is found by studying the angular distribution of the electroluminescence. The emission is modeled by accounting for optical interference. We account for birefringence of the anode layer in our model. The active polymer was, however, found to be isotropic. The anode consists of a single-layer of the conducting polymer complex poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonate) (PEDOT-PSS), with enhanced conductivity. As a cathode we use plain aluminum. By using only PEDOT-PSS we avoid having a thin metal layer or indium-tin-oxide as the anode in the path of the escaping light. The active material is a substituted polythiophene with excellent film forming properties. A comparison between the experimental and calculated angular distribution of light emission from a single-layered polymer light-emitting diode was shown to be in good agreement for the spectral region studied. By assuming a distribution of the emission zone, we deduce the position as well as the width of the zone.