摘要:

Voltage‐controlled optical bistable laser operation is demonstrated for the first time using nonlinear optical absorption of two‐dimensional excitons in a GaAs‐AlGaAs multiple quantum well (MQW) laser. The laser used here is the conventional MQW laser diode but with tandem electrode configuration. TheL‐Icurve of light output as a function of current injected into one segment of electrodes can be changed by a bias voltage applied to the other segment of electrodes. At the onset of laser oscillation, a hysteresis loop appears, the shape of which depends strongly on the applied bias voltage. This bistability is ascribed to the nonlinear absorption of two‐dimensional excitons.

ISSN:0003-6951    

DOI:10.1063/1.97614

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report on an efficient semiconductor laser array pumped by a high‐energy electron gun. A peak power of 350 kW in a 4‐ns pulse has been measured from a 25‐mm2CdS laser. For the materials studied (CdS, ZnxCd1−xS, and ZnSxSe1−x), laser action has been obtained in the blue‐green region of the spectrum.

ISSN:0003-6951    

DOI:10.1063/1.97090

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report the first optically pumped mode‐locked Al0.3Ga0.7As/GaAs multiple quantum well (MQW) laser in external cavity. The MQW structure with a total thickness of 5 &mgr;m was grown by molecular beam epitaxy on a Si‐doped GaAs substrate and was synchronously pumped by a mode‐locked Kr+laser (82 MHz) at 647.1 nm. The MQW laser emitted 10 ps pulses at 8085 A˚ with peak powers as high as 6 W. The demonstrated MQW laser combines desirable properties of quantum wells with advantages of an external cavity, such as specific band‐gap design with high beam quality and the possibility of intracavity tailoring of the laser beam.

ISSN:0003-6951    

DOI:10.1063/1.97091

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The low‐frequency limit of Biot’s theory of fluid‐saturated porous media predicts that the coefficients for viscous attenuation of shear waves and of the fast compressional wave are proportional to the fluid permeability. Although the observed attenuation is generally in qualitative agreement with the theory, the magnitude of the observed attenuation coefficient in rocks is often more than an order of magnitude higher than expected. This apparent dilemma can be resolved without invoking other attenuation mechanisms if the intrinsic permeability of the rock is inhomogeneous and varies widely in magnitude. A simple calculation of the overall behavior of a layered porous material using local‐flow Biot theory shows that the effective permeability for attenuation is the mean of the constituent permeabilities while the effective permeability for fluid flow is the harmonic mean. When the range of variation in the local permeability is one or more orders of magnitude, this difference in averaging method can easily explain some of the observed discrepancies.

ISSN:0003-6951    

DOI:10.1063/1.97092

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The first demonstration of a fuel density‐radius product measurement using secondary nuclear fusion reactions is presented. This technique involves using neutrons and protons generated by DT {T(d,n)&agr;} and D3He {3He(d,p)&agr;} fusion reactions, respectively, in a pure deuterium fuel.

ISSN:0003-6951    

DOI:10.1063/1.97093

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Silicon‐germanium alloys are found to be simple model systems for studying the effects of melting temperature changes on the liquid‐solid interface dynamics during pulsed laser melting. The melting temperature of these alloys can be continuously varied from 1210 to 1685 K. An alloy of Si50Ge50is shown to closely model the melting kinetics of amorphous silicon. By tailoring the melting temperature versus depth with multilayer structures, the effects of superheating, undercooling, and thermal conductivity on the solidification dynamics have been studied.

ISSN:0003-6951    

DOI:10.1063/1.97094

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report in this letter on an interesting and unexpected effect which is not fully understood yet. Strong hydrogen‐implanted accumulation layers on ZnO surfaces, produced and maintained at 80 K, can be further enhanced by illumination with visible light. The enhancement attained is surprisingly large, amounting to a twofold increase in surface electron density, up to 6×1014cm−2. The photoenhanced layer is less than 10–20 A˚ in width, thus constituting a two‐dimensional electron system, which is by far the strongest ever attained on any semiconductor surface. Measurements of the electron transport characteristics and of the spectral response of the photoenhancement process are presented.

ISSN:0003-6951    

DOI:10.1063/1.97095

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report the first preparation of indium phosphide using flow modulation techniques in the hydride vapor phase epitaxial system. A conventional single barrel reactor was used. Layer growth rates as low as 25 A˚/cycle were demonstrated. Room‐temperature carrier concentrations for the unintentionally doped InP of 5×1015cm−3and electron mobilities of 3650 cm2/V s were achieved.

ISSN:0003-6951    

DOI:10.1063/1.97096

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Up to 20 dB of photocurrent amplification with a frequency response of 2 GHz has been observed in GaAs Schottky photodiodes. The amplification may be caused by a reduction in Schottky built‐in potential under illumination. The device may find application in improving the sensitivity of optical receivers.

ISSN:0003-6951    

DOI:10.1063/1.97097

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Electrical conductivity measurements ona‐Ge:H/a‐Si:H superlattices parallel and perpendicular to the layers are explained by a simple quantum well model which yields effective electron masses 0.4m0fora‐Ge:H and 0.3m0fora‐Si:H. Space‐charge‐limited currents observed at high fields are used to determine the density of deep gap states in thea‐Ge:H layers.

ISSN:0003-6951    

DOI:10.1063/1.97098

出版商:AIP    

年代:1986

数据来源: AIP