摘要:

Employing self‐consistency, the multiple‐scattering problem is formulated for periodic arrays of particles having constitutive parameters distinct from those of the embedding material. AT‐matrix description of individual particle scattering is employed, so that particles need not be spherical. Explicit analytical and numerical results are obtained for the effective complex dielectric constant &egr;¯ and permeability &mgr;¯ in the quasistatic and infinitesimal lattice limits for several lattice geometries, and shown to agree with existing static computations under appropriate conditions. Random arrays are also considered briefly, and the role of single‐particle resonance effects is examined. Finally, longitudinal electric and magnetic waves are predicted to exist at certain discrete frequencies where &egr;¯ or &mgr;¯ vanish.

ISSN:0021-8979    

DOI:10.1063/1.336988

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

From picosecond pump‐probe and forward degenerate four‐wave mixing (DFWM) experiments, we obtain the near‐band‐gap nonlinear absorption and refraction properties of GaInAsP for &lgr;∼1.5 &mgr;m. Using a mode‐locked color center laser, the nonlinear signals are studied in room‐temperature samples as a function of time and wavelength for different pump energies and for materials with different band‐gap energies. Nonlinear absorption cross sections &sgr;ehas large as −5.7×10−15cm2are obtained from the pump‐probe results, while effective nonlinear cross sections &sgr;effas large as 7.8×10−16cm2(corresponding to a steady state ‖&khgr;(3)‖∼3.8×10−3esu for a 20‐ns relaxation time) are measured in the DFWM experiments. The spectral behavior of the data shows that above the band gap, the nonlinearity is due both to band filling and screening of excitonic effects. However, the effectiveness of the screening diminishes within one or two plasma frequencies of the band edge.

ISSN:0021-8979    

DOI:10.1063/1.336989

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Transmission electron microscopy of proton‐exchanged LiNbO3waveguide channels reveals regions of diffuse intensity within the single‐crystal electron diffraction patterns of LiNbO3. The diffuse intensity was not observed from areas of LiNbO3which had been masked with Cr before exchange. Heating the waveguides in air at 550 °C for 2 h sharpened some of the diffuse intensity into diffraction spots, some of whose lattice spacings matched Nb2O5or LiNb3O8. Other reflections also appeared which matched these phases. Small (∼20 nm diam) cavities were also observed in the exchanged channels after heating and suggest the occurrence of a dehydration reaction.

ISSN:0021-8979    

DOI:10.1063/1.336965

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The single‐particle trajectories of relativistic electrons in a magnetic field configuration which consist of a periodic wiggler field produced by a helical winding of two wires (‘‘dipole’’ magnetic field) superimposed on a helical winding of four wires (continuously rotating ‘‘quadrupole’’ magnetic field) are studied. The orbit equations can be reduced to a system of linear, inhomogeneous differential equations for variables related to transverse velocities. These equations are solved exactly and the stability region for the electron orbits in wide range of the parameters is obtained.

ISSN:0021-8979    

DOI:10.1063/1.336966

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We calculate the three‐dimensional light distribution in the focal region of a lens in the presence of absorption. The results are directly applicable to the optical generation of carriers in a semiconductor. A generation volume for these carriers is introduced and its dependence on focus position is investigated.

ISSN:0021-8979    

DOI:10.1063/1.336967

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper reports the results of structural analysis of proton‐exchanged lithium niobate optical waveguides fabricated inZ‐,X‐, andY‐cut substrates immersed in pure benzoic acid. Rutherford backscattering spectrometry, nuclear reactions, secondary ion mass spectrometry, scanning electron microscopy, and x‐ray diffraction were used to measure atomic composition profiles and the marked lattice distortion induced by the proton exchange process in the waveguiding layer. H and Li concentration measurements indicate an exchange of about 70% of the Li atoms are present in the virgin LiNbO3crystal.

ISSN:0021-8979    

DOI:10.1063/1.336968

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have studied the phenomenon of light propagation in an optically active linearly birefringent medium with particular reference to the electro‐optic crystal of Bi12SiO20. Analytic expressions are given for the ellipticity and the orientation of the emerging light vibration when linearly polarized light is incident normally on the crystal. From these expressions we derive the interesting results that there exists an orientation of the incident light vector for which the output beam is linearly polarized and that the input and output linear vibrations are then symmetrically oriented with respect to the principal birefringent axes of the crystal. This particular angle of orientation is expressed in terms of the linear and circular birefringence of the crystal. Since ellipticity is a function of the electric‐field‐induced linear birefringence and hence of the electro‐optic coefficient of the crystal, we have determined the electro‐optic coefficientr41from a measured value of the ellipticity. The coefficientr41is found to be (4.1±0.1)×10−12m/V.

ISSN:0021-8979    

DOI:10.1063/1.336969

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The electric conduction in polyethylene naphthalate film was investigated under high electric fields. The current strongly depended on the electrode materials, especially on the cathode metal. Schottky‐injection current was observed in the specimen with an Al cathode at the fields less than 106V/cm, while at higher fields (>106V/cm) tunneling‐injection current and electroluminescence were observed simultaneously, suggesting the impact ionization by electrons injected from the electrode.

ISSN:0021-8979    

DOI:10.1063/1.336970

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Reflection of Rayleigh surface waves by shallow grooves or metallic strips on general anisotropic crystals is analyzed. In this paper, the groove or strip is considered as a small discontinuity which acts as a surface excitation source for the scattering of the incident wave. The problem is solved by using Fourier transform technique and integration in the complex plane. Reflection coefficients of the various geometries on quartz and lithium niobate are calculated in good agreement with experiment.

ISSN:0021-8979    

DOI:10.1063/1.336971

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A composite acoustic resonator consisting of a buffer and a sample is considered in the present paper. A numerical analysis was accomplished for finding out the resonance conditions. Although complicated expressions were obtained, the composite resonator can be used for nondestructive testing of materials in a relatively simple manner. It is shown that if the acoustic and elasto‐optic parameters of the buffer are known, one can find out those of the sample using the diffraction of a laser beam from the acoustic field in the buffer. Good agreement was obtained between the theoretical and the experimental results in the case of a fused quartz‐dense flint system. It is shown that attenuation coefficient elasto‐optic constants and velocity of propagation can be measured with satisfactory accuracy with the help of the composite acoustic resonator.

ISSN:0021-8979    

DOI:10.1063/1.336972

出版商:AIP    

年代:1986

数据来源: AIP