摘要:

The sharply convergent acoustic beam used in the scanning acoustic microscope can provide sufficient intensity to produce strong nonlinear effects at microwave frequencies. Second harmonic acoustic radiation generated in the vicinity of the beam focus is readily detected and used to form an image of an object placed in the focal plane.

ISSN:0003-6951    

DOI:10.1063/1.88759

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Misfit dislocations introduced during LPE growth are shown to act as sinks for point defects introduced by 1‐MeV electron bombardment in Ga1−xAlxAs1−yPy/GaAsp+nheterojunctions. Electron‐beam‐stimulated dislocation motion was observed directly withinsituTEM studies on previously bombarded material. SEM measurements have correlated beam‐induced defect annealing with recombination‐enhanced defect motion. These results suggest that dislocation networks, which are active in the dark‐line‐defect degradation mode of heterostructure lasers, may form by a climb mechanism which is activated by the injection‐stimulated motion of point defects.

ISSN:0003-6951    

DOI:10.1063/1.88760

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A liquid crystal field‐effect light valve with high‐speed turn‐off operation is described. The three‐terminal device is symmetric in its turn‐on/turn‐off operation and uses digital rather than multifrequency addressing.

ISSN:0003-6951    

DOI:10.1063/1.88761

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We apply the theory of linear antennas to metal‐barrier‐metal (MBM) devices. An expression is derived for the optical voltage induced across the insulating barrier, taking into account that the metal conductivity is in the relaxation region for infrared and visible radiation. It is shown that the optical voltage should drop with frequency according to &ohgr;−3. This &ohgr;−3dependence suggests that we should look for new mechanisms in order to extend the usefulness of MBM devices into the visible region.

ISSN:0003-6951    

DOI:10.1063/1.88762

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An analysis of space‐charge‐limited counterstreaming flow of ions and electrons in a high‐voltage planar diode in the presence of a strong transverse magnetic field is presented. A two‐component one‐dimensional cold‐fluid model is used which includes most self‐consistent effects. A substantial enhancement of ion current by a factor of 3–6 is found at fields slightly larger than the critical magnetic insulation field.

ISSN:0003-6951    

DOI:10.1063/1.88763

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

It has been found that the stable flow of a magnetically focused unneutralized intense relativistic electron beam (IREB) depends on beam front parameters (e.g., current and voltage rise times) and on the geometry of the propagation region (e.g., length). It is argued in this letter that a pulsed IREB is susceptible to a two‐stream instability resulting from reflection of electrons from the beam front. This effect may have to be taken into account in IREB applications involving fast rise times and/or long drift lengths, such as ion accelerators, electron autoaccelerators, and intense microwave generators.

ISSN:0003-6951    

DOI:10.1063/1.88764

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We have used transmission electron microscopy to study crystalline defects in Si wafers which were first implanted with Si ions to produce an amorphous surface layer and then annealed to produce epitaxial regrowth. The original high degree of crystalline perfection is not entirely recovered. In the implanted layer, small defect clusters, interstitial loops, and large half‐loops have been observed. The density, distribution, and characteristics of these defects have been determined.

ISSN:0003-6951    

DOI:10.1063/1.88765

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The physical state of W implanted in Cu has been studied by4He+ion channeling and transmission electron microscopy. At implant concentrations ≲1 at.%, W is in solid solution but may form elemental bcc precipitates on annealing to ≳450 °C. For implant concentrations of ∼10 at.%, a disordered layer of Cu and W is formed with the W occupying no regular lattice sites; on annealing W precipitates are formed with dimensions of a few hundred angstroms.

ISSN:0003-6951    

DOI:10.1063/1.88766

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Accurate matching of propagating constants (or phase matching) of TE0and TM0modes has been demonstrated in birefringent waveguides prepared by reactively sputtering tantalum in O2/N2mixtures. Exact phase matching occurs at a guide thickness of 3926 A˚ for films with indices of 1.884 and 1.914 on glass substrates. For a coherence length ⩽1 cm, corresponding to a difference in normalized propagation constants, &Dgr; (&bgr;/k), of 3×10−5, the thickness must be within 20 A˚ of this value and this has been reproducibly obtained after calibration of the deposition rate. Reduction of &Dgr; (&bgr;/k) to within 6.3×10−6has been demonstrated. These techniques can be extended to the fabrication of active polarization converters.

ISSN:0003-6951    

DOI:10.1063/1.88741

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Two‐photon absorption is measured using two picosecond pulses: a monochromatic pulse and a pulse with broad frequency spectrum. Single pulses of high peak intensity were applied to crystalline samples without damage. Introducing a time delay of several picoseconds between the two pulses, possible two‐step processes can be elucidated. As an example, two‐photon absorption in CdS was investigated over an energy range from 2.4 to 3.5 eV.

ISSN:0003-6951    

DOI:10.1063/1.88742

出版商:AIP    

年代:1976

数据来源: AIP