摘要:

This paper presents a detailed study of the waveguide and plasmon polariton properties of four-layer systems involving highly doped semiconductor material. The dispersion relations of waveguide and plasmon polariton modes are calculated for different geometrical parameters and material properties. Special attention is paid to the transition region between the latter modes, which exhibits a complex behavior. Slab plasmon polaritons at wavelengths slightly larger than the plasma wavelength, yielding a positive real part of the permittivity, have been found. Finally, applications at wavelengths near the transition region and near the plasma wavelength are proposed and discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363842

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

New cinnamic acid type nonlinear-optical (NLO) photopolymers and their use in frequency doubling Cerenkov waveguides are reported. Cerenkov configurations are shown to be particularly appropriate for efficient second-harmonic generation in NLO polymers. Analysis of Cerenkov waveguides in three-layer configurations allows optimization of their performance with respect to polymer layer thickness and substrate parameters. The NLO efficiencies predicted from the model and from independently determined NLO material parameters are qualitatively in agreement with the experimentally observed large Cerenkov NLO efficiency of 0.2&percent; W−1 cm−1. We show further that improved device performance results from novel four-layer waveguide configurations. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363997

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A method for measuring the effective birefringence of polymer lightguides is shown to be a useful tool for chemical sensors. It is demonstrated that the method can be either the nonlinear response of an initially anisotropic lightguide on a linear effect of an in-diffusing compound or a stress induced birefringence in an initially isotropic polymer film. The samples used were polyimide for the anisotropic case and the allyl polymer poly(diallylic terephtalic acid) for the isotropic material. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363840

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We investigate the form birefringence due to photoinduced one- and two-dimensional volume index gratings in DuPont photopolymers. The effective medium theory has been applied to the continuous volume subwavelength gratings. With the presence of a one-dimensional volume subwavelength grating, the originally isotropic photopolymer exhibits a negative form birefringence and behaves like a uniaxial dielectric. A form birefringence of −1.2×10−3at &lgr;=632.8 nm is measured at a grating period of &Lgr;=447 nm. Experimental results on the dispersion of the form birefringence versus the illumination wavelength and the grating period are presented. With the presence of a two-dimensional grating, in general, the originally isotropic photopolymer exhibits a biaxial form birefringence and behaves like a biaxial dielectric. Positive form birefringence can also be obtained by recording two volume gratings with different grating wave vectors. By recording two photoinduced volume gratings we can synthesize biaxial dielectrics with the principal axes along any desired directions. We also report the measured principal refractive indices of the medium due to the presence of two-dimensional volume gratings in DuPont photopolymer. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363989

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A numerical simulation of an optically pumped, multimode D2O laser was carried out based on Lamb’s semiclassical laser theory. The numerical code includes the dispersion effect of the laser medium (D2O gas in the cavity) in order to simulate the strength of mode coupling accurately. As a result, multiple-longitudinal-mode oscillations around the Raman resonance frequency were obtained that are roughly in agreement with experimental observations. Energy spectra of the D2O laser emission obtained by the simulation were compared with those of the experimental results for various D2O gas pressures. By including the dispersion effect, temporal variations of mode frequencies were calculated. In addition, resonant pumping was examined to obtain spectrally narrow outputs by tuning a frequency of a pump CO2laser pulse to the line center of the absorption band of D2O molecules. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364111

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The kinetics of dusty plasma in low pressure rf discharges is studied by solving self-consistently the time dependent electron Boltzmann and dust charging equations. The electron temperature, the excitation and ionization rate coefficients, and the dust particle charge are shown to be modulated in the periodic state. It is demonstrated that the presence of dust particles enhances the modulated amplitude, reduces the high energy content of the electron energy distribution, the corresponding effective electron temperature, and the electron excitation and ionization rate coefficients. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364124

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A very high silane dissociation rate (⩾95&percent;) has been measured using mass spectrometric analysis of neutral species in a low pressure (a few mTorr) high density (⩾1011cm−3for a radio frequency source power of 800 W) oxygen/silane (O2/SiH4) helicon deposition reactor. Energy selective mass spectrometric measurements of positive ions have been performed for O2/SiH4flow rate ratios varying from 1 to 10 and for a constant power of 800 W. A simple model of the ion-induced deposition rate has been developed and the results have been compared to the measured deposition rate. It appears that 20&percent;–50&percent; of the silicon atoms in the near-stoichiometric deposited oxides could result from the flux of silicon-containing ions (essentially Si+and SiOH+) to the substrate during deposition. An oxidation process via O2+ions and an etching process via H3+ions could possibly be involved in the ion-induced deposition mechanism. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364103

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Transient Langmuir probe measurements of the plasma density, electron temperature, and plasma potential during “slow quenching’’ of a Cs–Ba tacitron at two different discharge conditions were made. Following the application of a negative voltage pulse on the grid, the grid aperture sheaths initially grew then shrank temporarily, due to an increase in the ion flux from the grid-collector region, then grew again until the discharge eventually extinguished. Discharge extinguishing occurred when the effective ionization cross section became decoupled from the continually rising electron temperature; hence, the discharge could not be maintained owing to the decrease in the ionization rate. This inability to maintain the discharge is considered the mechanism for extinguishing by slow quenching. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364128

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A model was developed to simulate the effects of heavy charged-particle (HCP) radiation on the information stored in three-dimensional computer optical memories. The model is based on (i) the HCP track radial dose distribution, (ii) the spatial and temporal distribution of temperature in the track, (iii) the matrix-specific radiation-induced changes that will affect the response, and (iv) the kinetics of transition of photochromic molecules from the colored to the colorless isomeric form (bit flip). It is shown that information stored in a volume of several nanometers radius around the particle’s track axis may be lost. The magnitude of the effect is dependent on the particle’s track structure. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364096

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a one-dimensional simulation methodology for determining the liquid crystal director distribution in a cell for arbitrary pretilt angles on two glass substrate surfaces. The method is illustrated for cases of an asymmetric twisted nematic cell, a hybrid alignment nematic cell, and a bend alignment nematic cell. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364097

出版商:AIP    

年代:1997

数据来源: AIP