摘要:

Coupled‐waveguide optical modulators with Schottky contacts are proposed in two waveguide configurations, namely, in the embedded‐waveguide configuration and in the rib‐waveguide configuration. It is shown that the heterostructured embedded‐waveguide device is suitable for efficient modulation and that the homostructured rib‐waveguide device has fairly small modulating power per bandwidthP/&Dgr;fin spite of its simpler structure. GaAs homostructured rib‐waveguide devices were fabricated, and optical modulation was carried out at a light wavelength of 1.06 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.324496

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Normal‐mode analysis is presented to study wave propagation along general anisotropic elastic waveguides. Introducing a concept of material perturbation, normal modes of these general waveguides are successfully examined in terms of those of a conveniently defined ’’reference waveguide’’ with simpler material parameters. Employing the Rayleigh‐Ritz variational technique, a coupled‐mode equation is deduced, and the solution interprets the desired propagation property as a mode coupling between normal modes of the reference waveguide. Considering the case of two‐mode coupling, the mode conversion is analyzed in some detail. The results are applied to the case of a specific waveguide with a YIG film on an isotropic substrate. This example suggests the possibility of a ’’Rayleigh‐Love wave mode converter’’. Numerical calculations about some basic properties of this device are presented also.

ISSN:0021-8979    

DOI:10.1063/1.324497

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The treatment of the surface of an alumina insulator with a Mn/Ti coating significantly increases its voltage‐holdoff capability. Insulators treated with this coating had vacuum‐holdoff voltages about 25% higher than did untreated insulators. During processing (quasimetallizing) the coating penetrates into the alumina, so it is fairly insensitive to damage by abrasion or electrical breakdown. The quasimetallized coatings is also comparable with subsequent metallizing and brazing of the alumina insulator. We conclude that the coating (1) decreases the surface resistivity of the insulator, (2) decreases the insulator’s secondary‐electron‐emission yield, and (3) makes the surface of the insulator dielectrically more uniform.

ISSN:0021-8979    

DOI:10.1063/1.324498

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The ultrafast streak camera is presently the only comprehensive temporal diagnostic tool available for laser‐fusion studies. An internally emplaced CCD readout system has been designed to minimize the data reducing complexity, cost, and time delay associated with the present phosphor/intensifier/film readout technique. Experimental results using the front‐illuminated Fairchild 202 CCD and the back‐illuminated RCA SID 52501 CCD for direct imaging of the streak‐camera photoelectrons are presented. The important sensor requirements which optimize the performance of the CCD in the streak‐camera application have been defined.

ISSN:0021-8979    

DOI:10.1063/1.324499

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An investigation of the effect of velocity/temperature boundary layers on the conductivity and the power output of an MHD generator has been presented in this paper; the analysis is based on the Boltzmann transfer equation. It is seen that the conductivity and the mean power output per unit volume of an MHD generator becomes considerably reduced because of the presence of the velocity and temperature boundary layers. The power output is found to decrease sharply with boundary‐layer thickness for low values of the thickness and levels off at larger thicknesses.

ISSN:0021-8979    

DOI:10.1063/1.324500

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The deformation of Si‐doped GaAs single crystals with a carrier concentration of 1018cm−3was investigated by determining the stress/strain relationships for &agr; and &bgr; bending at 500 °C. Marked differences were found between the &agr; and &bgr; deformation curves. Using Gilman and Johnston’s model for dislocation multiplication and combining it with a linear relationship between the dislocation velocity and applied stress, a theoretical model was developed to explain the above‐mentioned differences in terms of dislocation mobilities &mgr;, dislocation multiplication factorsC, activation stresses &tgr;a, and the initial densities of dislocation sources &rgr;0. Applying a numerical curve fitting procedure to the experimental curves, these parameters were found to have the following values for &agr; and &bgr; bending, respectively: &mgr;&agr;=8.5×10−12and &mgr;&bgr;=3.8×10−12cm3 dyn−1 sec−1;C&agr;=89 andC&bgr;=130 cm−1; &tgr;a&agr;=2.11×108and &tgr;a&bgr;=2.7×108dyn cm−2; &rgr;0&agr;=9×105and &rgr;0&bgr;=4.5×102cm−2.

ISSN:0021-8979    

DOI:10.1063/1.324501

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The centroids for distributions of various ions important in Si technology (Al, P, and As) implanted at energies from 5 to 100 keV and a fluence of 1×1013cm−2into 1300–1400‐A˚‐thick SiO2layers of metal‐silicon dioxide‐silicon (MOS) structures have been located by using measurements of the photocurrent as a function of the gate voltae which is called the photoI‐Vtechnique. This technique senses trapped electrons on sites related to the implanted ions after charging by avalanche injection. A high‐temperature (1000 °C in N2for 30 min) premetallization anneal was used in order to minimize trapping on atomic displacement damage sites which could give a different centroid than that of the ion distribution. Good agreement of the trapped electron centroid deduced from the photoI‐Vtechnique with calculations of the ion centroid based on the theory of Lindhard, Scharff, and Schio&slash;tt (LSS) and with independent experimental determinations of the ion centroid from profiles using secondary ion mass spectroscopy (SIMS) or He+ion backscattering was found in most cases. The photoI‐Vtechnique is shown to have distinct advantages over most techniques which directly measure the ion distribution or centroid like SIMS and He+ion backscattering because of its nondestructive nature, minimally perturbing effect, and extremely low detectability limit of 1011charges/cm2or less. The empirical relationship observed by Chu, Crowder, Mayer, and Ziegler for ion implantation into various amorphous insulators between the LSS normalized centroid &rgr; and the LSS normalized energy &egr; of &rgr;=2.7&egr; has been shown for the first time to be valid for &egr;?0.4.

ISSN:0021-8979    

DOI:10.1063/1.324510

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The stress field of an edge dislocation lying in the midplane of an isotropic plate of thickness 2awith free surfaces is calculated. The Burgers vectorblies in the plane of the plate. The field is calculated as the sum of two terms: the stresses of the dislocation in an infinite medium together with an array of images which annul the tangential tractions, and the stresses which annul the normal tractions and are derived from a stress function given by a convergent Fourier integral. The long‐range bending of the beam depends only on the integral and agrees with Eshelby’s result. The energy of interaction with a similar dislocation at a distanceXacan be expressed by a Fourier integral alone. If this integral is evaluated by the method of residues, the asymptotic form for largeXis given by the poles of the integrand with the smallest positive real parts. These do not lie on the imaginary axis; the asymptotic form, therefore, shows damped oscillations ∼3.0075bD sin(1.3843X+0.1175) exp(−3.7488X). The first minimum occurs atX?2.4.

ISSN:0021-8979    

DOI:10.1063/1.324511

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A Fourier‐transform method is used to obtain the displacement field for an edge dislocation. The method reproduces known results and produces new solutions that can be compared with those from atomistic models of edge dislocations.

ISSN:0021-8979    

DOI:10.1063/1.324512

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The property of single halogen interstitials as the hardening agent has been studied through experiments using KBr doped with alkali impurity. Thermal recovery of the radiation‐induced increment of the flow stress &Dgr;&tgr;, and the thermal annealing of color centers in KBr : Na and KBr : Li are measured by means of an isochronal pulse‐annealing technique. Single‐intersititial‐type centers,HAandIAcenters, decay at nearly the same temperature around 100 K in KBr : Na and around 210 K in KBr : Li, which is accompanied by the decrease of a considerable amount of &Dgr;&tgr; in both samples. The effects of optical illumination at 77 K on the thermal recovery of &Dgr;&tgr; and on the concentration of color centers are also examined to prove the responsibilities of theHAandIAcenters for the hardening effect. It is shown that theIAcenter is more resistant to dislocation movements than theHAcenter.

ISSN:0021-8979    

DOI:10.1063/1.324513

出版商:AIP    

年代:1978

数据来源: AIP