摘要:

Acoustical image holograms have been recorded at 3.6 MHz using a specially designed nematic liquid crystal convertor. These holograms are reconstructed with He‐Ne laser light. The figures presented illustrate the practicability of the system, particularly in the field of nondestructive testing.

ISSN:0003-6951    

DOI:10.1063/1.97124

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The effectiveness of surface recombination in speeding up the relaxation of a GaAs e´talon is reported. Various thickness (1.5, 0.5, 0.3, 0.13 &mgr;m) bulk GaAs windowless samples were fabricated and tested as optical logic gates. Times for complete recovery of transmission lie between 400 and 30 ps. The response shows a roughly linear increase in speed as the sample thickness decreases, consistent with surface recombination being the dominant relaxation mechanism. A very fast cycle time of 70 ps is demonstrated using a 0.3‐&mgr;m‐thick windowless GaAs e´talon as an all‐optical logic device. Proton‐bombarded samples show slower recovery and poorer contrast, and they require more gating energy.

ISSN:0003-6951    

DOI:10.1063/1.97125

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We propose using single crystal multilayers of AlAs, GaAs, and AlxGa1−xAs for use as several different kinds of optical interference elements which include high reflectors, transmission filters, and Fabry–Perot cavities. We have grown many of these structures by molecular beam epitaxy and measured their optical characteristics. We find the characteristics of these structures to be very useful for a number of applications for integrated optical devices which we also propose.

ISSN:0003-6951    

DOI:10.1063/1.97126

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The ultrasonic dispersion characteristics of vertically polarized plate waves in fluid‐coupled plates of unidirectional graphite‐fiber reinforced epoxy have been found experimentally to display anomalous dispersion. This anomaly consists of a mixing of the two fundamental plate modes at phase velocities near the bulk composite transverse wavespeed. A calculation of ultrasonic reflection from a fluid‐coupled composite plate accounts very well for the previously unreported experimental observations. It is demonstrated that the anomalous dispersion is a consequence of the presence of the fluid and is strongly enhanced by the highly anisotropic elastic nature of the composite. It is further shown that a much weaker manifestation of the effect also exists in fluid‐coupled plates of elastically isotropic materials.

ISSN:0003-6951    

DOI:10.1063/1.97127

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A low pressure glow discharge switch that has a number of features that are desirable for high power applications is described. The switch has achieved high stand‐off voltage and peak current, has potential for very fast current rate of rise, and operates near the glow‐to‐arc transition in hydrogen or helium. Closure is initiated by light incident on the back of the cathode, and it is observed that surface damage within the area of illumination is less than surrounding areas. Several aspects of the switch are similar to thyratrons and pseudosparks.

ISSN:0003-6951    

DOI:10.1063/1.97128

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Ion beam mixing yielded a distinct enhancement in the sliding life of sputtered MoSxfilms without any deterioration of the excellent lubrication properties. This effect occurs only at higher ion energies indicating an improved film‐substrate adherence caused by a mixing of the interface, which was confirmed by secondary ion mass spectrometry and topographical investigations. In addition to that a considerable enhancement of the film density was found due to a reorientation of the MoSxplatelets which led also to an improvement of the effective film thickness.

ISSN:0003-6951    

DOI:10.1063/1.97129

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Magnetoresistance, Hall coefficient, and thermal diffusivity of new high‐quality graphite films prepared by pyrolysis of a condensation polymer, poly( p‐phenylene‐1,3,4‐oxadiazole) were measured. The total carrier density, mobility, and thermal conductivity were 1.6×1019cm−3, 7400 cm2 V−1 s−1, and 11 W cm−1 K−1for the graphite film annealed at 3000 °C, which are almost comparable to those of highest quality graphites known so far. Drastic changes in the electronic and thermal properties with the heat‐treatment temperature were found and discussed in relation to the development of the high‐quality graphite.

ISSN:0003-6951    

DOI:10.1063/1.97130

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Results of rapid (laser induced) and slow (heating stage induced) crystallization studies on Te1−xGex, 0≤x≤0.6, are reported. The time it takes to laser crystallize varies withxby more than four orders of magnitude. Films with stoichiometric compositions, Te and GeTe, can be crystallized using laser pulses of less than 100 ns duration. Unlike Te, which spontaneously crystallizes at room temperature, GeTe has a crystallization temperature of >150 °C. From these results we argue that, in general, compound materials allow realization of fast‐switching, reversible, phase‐change optical recording media. Furthermore, this fast‐switching capability, from the amorphous to the crystalline state and back, can be attained simultaneously with long term data (amorphous phase) stability, provided the melting temperature of the compound is sufficiently high.

ISSN:0003-6951    

DOI:10.1063/1.97617

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Thin titanium nitride (TiN) and zirconium nitride (ZrN) films containing excess nitrogen up to 62 and 65 at. % N, respectively, were deposited on austenitic stainless steel sheet substrates by triode ion plating at about 823 K. The nitrogen content of the films was determined using the nuclear resonance broadening technique based on the15N(p,&agr;&ggr;)12C nuclear reaction and x‐ray diffraction was used to study the phase compositions. Annealing experiments in evacuated quartz tubes were carried out at 773 and 1173 K to test the stability of the coatings. The results showed no essential differences for TiN before and after heat treatment. Slight indications of diffusion accompanied with the transformation of remaining &agr;‐Zr to ZrN were found in the case of ZrN films after heat treatment at the higher temperature of 1173 K.

ISSN:0003-6951    

DOI:10.1063/1.97131

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

It is found experimentally that a balance between the chemical force and the force due to an applied electric field acting on fractionally charged cesium particles on the surface of silicon leads to an equilibrium state. Measurements of the coverage gradient (∂&thgr;/∂x) in this equilibrium state give a relation between the gradient of the chemical potential (mainly the binding energyUb) and the fractional charge of the cesium particles. For cesium atoms on silicon this relation is found to bef=0.16∂Ub/∂&thgr;+0.03.

ISSN:0003-6951    

DOI:10.1063/1.97132

出版商:AIP    

年代:1986

数据来源: AIP