摘要:

An integrated multilayer laser consisting of three double heterostructure GaAs laser diodes connected in series by reversed biasedp+n+tunnel junctions have been grown by molecular beam epitaxy. The lasers operate at currents comparable to single double heterostructure lasers but at approximately three times the single laser voltage.

ISSN:0003-6951    

DOI:10.1063/1.93585

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The threshold current density, laser wavelength, grown layer thickness, reverse breakdown voltage, and far‐field radiation pattern as a function of position on the grown wafer are reported for broad area multiple quantum well GaAlAs heterostructure lasers grown by metalorganic chemical vapor deposition. It is found that the layer thickness varies across a 1.5‐in. sample by as much as 20% at the outer edges of the water, leading to a lasing wavelength shift of as much as 150 A˚ owing to the quantum size effect. It is shown that this thickness variation has only a small effect on the threshold current density across the water such that the uniformity of threshold current density is comparable to that reported previously for molecular beam epitaxy‐grown conventional double heterostructure lasers.

ISSN:0003-6951    

DOI:10.1063/1.93586

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We show that birefringence can be optically induced in hybrid aligned nematic (HAN) liquid crystals at normal incidence for light fields much lower than the Fredericksz threshold. In this case no threshold exists and the nonlinear optical effect at normal incidence is of the same order as that obtained with homeotropic (HOM) cells for the maximum useful angle. An analysis of the effect of the anchoring energyWsis worked out showing that weak anchoring on the walls enhances the nonlinear effect by one order of magnitude or more.

ISSN:0003-6951    

DOI:10.1063/1.93587

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The improved performance characteristics of a compact pulsed, atmospheric pressure CO2laser using He‐free, H2buffered gas mistures are reported. Both peak and average power are found to be optimal with this mixture as a result of an enhanced gain amplitude and rise time. A ∼2.7‐cm3discharge has produced 17‐W average laser power at ∼300 Hz.

ISSN:0003-6951    

DOI:10.1063/1.93588

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Optical waveguides fabricated in LiNbO3by what has previously been described as silver‐lithium or thallium‐lithium ion exchange in the molten nitrates AgNO3or TlNO3have not generally been reproducible. We show that the large increases of the extraordinary index (&Dgr;ne= 0.12), which are observed intermittently, result not from introduction of the heavy ions, Ag+or Tl+, but from hydrogen‐lithium exchange, which occurs when hydrogen is present as an impurity in the melts.

ISSN:0003-6951    

DOI:10.1063/1.93589

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A one‐dimensional theory of the generation of ultrasonic waves by photoacoustic absorption in a composite structure is described. The model consists of a backing material, an absorbing bulk or surface film, and a sample. Variations of ultrasonic amplitude and intensity with structure dimensions, optical absorption coefficient, frequency, and material parameters are discussed and compared with reported experimental data. It was found that the important material group—for both backing and film or sample—is &agr;(D)1/2, where &agr; is effectively a thermal‐expansion coefficient andDis the thermal diffusivity. The relevance of the parameters in the heated volume to imaging is discussed.

ISSN:0003-6951    

DOI:10.1063/1.93590

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Some observational results on the XeCl excimerB→Xfluorescence and laser emissions from dilute Ne/Xe/HCl mixtures in a very small volume (∼1 cm3) pulsed avalanche discharge of ∼200‐ns duration at high current densities (0.6< j<1.8 kA/cm2) and at high gas pressures (2< p<11 atm) are presented. With increasing  j,p, and Ne dilution, the fluorescence pulse duration becomes more and restricted but the laser peak power continues to show an upward trend untilp≊8 atm. In spite of the short pulse and low extraction efficiency, laser peak power of up to ∼10 kW has been observed from the ∼1‐cm3volume discharge.

ISSN:0003-6951    

DOI:10.1063/1.93572

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The presence of a magnetic filter in a multicusp ion source reduces the transport of tungsten to the extractor region by forming a uniform plasma potential region in the source chamber. Because of the reduced numbers of primary electrons in the extraction chamber, the plasma grid floats near the plasma potential and this reduces the amount of impurity ions formed from sputtered grid material.

ISSN:0003-6951    

DOI:10.1063/1.93573

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

An eight‐chord interferometer array, together with a single‐chord interferometer separated toroidally by 90°, shows propagating global plasma density disturbances in the final 1 ms prior to discharge termination in ZT‐40M. A time‐delayed correlation technique applied to the nine‐chord data allows reconstruction of the shape of the propagating disturbance and discriminates against competing random density fluctuations.

ISSN:0003-6951    

DOI:10.1063/1.93574

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Intense charged particle beams in plasmas are subject to current limitation for single beam propagation. The limiting mechanism is excessive self‐focusing due to net current and space‐charge overneutralization effects. A nearly constant minimum plasma impedance of ∼30 &OHgr; is presented to beams with Lorentz factors &ggr;≳1.1.

ISSN:0003-6951    

DOI:10.1063/1.93575

出版商:AIP    

年代:1982

数据来源: AIP