摘要:

Thresholds have been measured for the breakdown of helium by laser radiation near 3.8 &mgr;m in wavelength. Four‐&mgr;sec chemical laser pulses were focused to a well‐defined spot 100 &mgr;m in diameter. Values of the instantaneous irradianceqtand the accumulated fluenceetoccurring at time of breakdown were observed as a function of helium pressure in the range 0.12–0.99 atm. The measuredqtwas 2.3 ×1010W/cm2at 1 atm, in good agreement with results scaled from other wavelengths.

ISSN:0021-8979    

DOI:10.1063/1.329849

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The photoionization process for UV‐initiated and UV‐sustained CO laser operation was investigated by measuring the photoion density produced by a single spark source using charge collection. C2H4and NO were studied as potential low‐temperature additives for enhancing photoion production, both of which photoionized by a single‐step process with a conversion efficiency of spark energy into photoionization of about 1%. The photoionization was also found to increase linearly with dissipated spark energy, was independent of the spark circuit parameters, and at constant gas and additive density was also independent of temperature.

ISSN:0021-8979    

DOI:10.1063/1.329850

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A high‐pressure (2×4×77) cm3UV‐sustained discharge was operated in a (1:3:9, CO:N2:He) gas mixture doped with either NO or C2H4. The electrical energy loading into the gas was parameterized with respect to the UV source energy, additive density, reduced temperature, and sustainer voltage. All the results were consistent with a discharge operated below the glow voltage and sustained entirely by photoionization. A maximum energy loading of about 400 J/liter was achieved.

ISSN:0021-8979    

DOI:10.1063/1.329851

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The preparation and operation of lattice‐matched Al0.48Ga0.52As/Ga0.47In0.52As/Al0.48In0@qL.52As double‐heterostructure lasers lasing at 1.65 &mgr;m grown on InP substrates by molecular‐beam epitaxy are described. The present result represents the first current injection semiconductor laser ever fabricated from the Al0.48In0.52As/Ga0.47In0.53As/Al0.48In0@qL.52As double heterostructure. Broad‐area Fabry‐Perot laser (0.15‐&mgr;m‐thick Ga0.47In0.53As active layer) with pulsed current threshold density as low as 3.3 kA/cm2has been obtained at room temperature and operated at heat‐sink temperatures as high as 115 °C studied. The threshold‐current temperature dependence has a characteristic temperature T0of 70 °C in the temperature range of 25°–115 °C.

ISSN:0021-8979    

DOI:10.1063/1.329852

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

All‐guided wave interferometers using [3×3] directional couplers as beam splitters are analyzed in detail. The characteristics of such interferometers are compared with those of conventional interferometers using [2×2] beam splitters. It is shown that there are advantages in using [3×3] couplers instead of [2×2] couplers in the Mach‐Zehnder interferometric sensors and the Sagnac rotation sensors (gyroscopes).

ISSN:0021-8979    

DOI:10.1063/1.329853

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Application of a surface coating to Corning 7059 glass thin‐film optical waveguides has been shown to significantly reduce their scattering loss. Combining the technique of CO2laser annealing of glass waveguides with surface coating, we measure waveguide loss as low as 0.01 dB/cm. By attributing the decrease in attenuation to elimination of the effects of surface irregularities, we were able to identify surface and bulk contributions to scattering losses in the original waveguide. By making such an identification before and after laser annealing, we confirm that CO2laser annealing of glass waveguides reduces both surface and bulk contributions to scattering losses.

ISSN:0021-8979    

DOI:10.1063/1.329854

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Liquids working in heat engines require especially effective thermal regeneration as they flow between the remote and ambient temperature regions of a machine. Using liquid Freon 114 (C2Cl2F4) as a test fluid, we have studied this process experimentally in a parallel‐plate geometry for the pulsating unidirectional flow of a Malone engine. A theoretical analysis of the thermohydrodynamical process is presented whose results compare favorably with experiment. For a constant average volume rate of flow of liquid, the regenerative loss decreases as the period of the engine decreases.

ISSN:0021-8979    

DOI:10.1063/1.329855

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A dynamic model of sintering by viscous flow has been developed in which viscous flow is treated as an analogue of incompressible, solid elastic behavior, using finite element analysis to transform the equivalent elastic problem to one of slow viscous flow. The sintering of an infinite line of cylinders was considered with surface morphology and neck size being monitored as a function of time. In general the model yielded higher neck growth rates than those reported in the literature based on static geometric approximations to the real neck curvature. This difference is shown to be due to the relatively small radii of curvature at the neck roots found in the present study, leading naturally to a greater driving force for sintering.

ISSN:0021-8979    

DOI:10.1063/1.329235

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

In a pulsed discharge, the temporal and radial behavior of the population densities of He(2 1S), He(2 3S), Hg(6 3P2), and Hg(6 3P0) is studied experimentally, and the time variation of the intensity of sidelight of Hg II at the 567.7‐ and 6 15.0‐nm lines is also measured with changing He partial pressure. The temporal and radial behavior of the laser action of a Hg ion laser is explained in terms of the temporal and radial behavior of the reactants in the Penning‐like excitation process, and furthermore, it is found that the populations of these reactants are dependent upon the distribution of the electron temperature.

ISSN:0021-8979    

DOI:10.1063/1.329236

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Using a pulsed afterglow technique, the excitation mechanism of the cw positive column He‐Te laser was investigated and a velocity averaged total destruction cross section of He+by tellurium was measured to be 1×10−15cm2. The principle channel for excitation of upper laser levels was seen to be charge transfer collisions between He+and Te atoms. These results are compared to similar measurements of upper laser levels of the positive column He‐Se laser, and the previous hollow cathode discharge measurements of He‐Te collisions as performed by Alienikov and Ushakov.

ISSN:0021-8979    

DOI:10.1063/1.329237

出版商:AIP    

年代:1981

数据来源: AIP