摘要:

The lock‐in threshold of a single‐mode 0.633‐&mgr; He&sngbnd;Ne laser was measured. Experiments were performed with a 1:1 mixture of the20Ne and22Ne isotope. The lock‐in threshold was found to increase with operation of the laser with smaller excess unsaturated gain. Minimum lock‐in threshold was found to occur at a higher frequency than the frequency at which the output power was a maximum. A rotational mode competition between the oppositely directed traveling waves was found for rotation rates less than the lock‐in threshold. The beam traveling with and against the direction of rotation was found to decrease and increase, respectively, with increasing rotation rate. Analysis showed that the single‐mode‐ring, laser equations, with mode coupling due to backscattering, satisfactorily explained the experiments.

ISSN:0021-8979    

DOI:10.1063/1.1658312

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A novel laser interferometric technique involving the use of an unstable external resonator is presented. The unstable resonator greatly facilitates electron density measurements in the presence of plasma density gradients transverse to the direction of beam propagation. The technique is used to obtain time‐resolved radial electron density distributions in the implosion stage of a linearz‐pinch discharge in argon at filling pressures of 0.1 and 1.0 Torr.

ISSN:0021-8979    

DOI:10.1063/1.1658313

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The electrical and optical properties of GaAs&sngbnd;GaxAl1−xAs injection lasers produced by solution epitaxy are described. These lasers are composed of three layers,n‐GaAs, a thinp‐GaAs layer, and ap‐GaxAl1−xAs layer. In these lasers, the threshold currentJthis a strong function of the width of thep‐GaAs layerd, being optimum wheredis about 2 &mgr;. The temperature dependence ofJthis comparatively small below some maximum temperatureTM, above which it increases very rapidly. The values ofJthobtained near room temperature for these lasers are lower than have previously been reported for injection lasers. Fabry‐Perot‐type diodes with cavities of about 400 &mgr; may be reproducibly prepared withJth(300°K) about 10 000 A/cm2. The lowestJth(300°K) observed for one of these units was 8600 A/cm2. Units with fully internally reflected modes can be reproducibly prepared withJth(300°K) ≈6000–7000 A/cm2. The lowJth(300°K) of these lasers is attributed primarily to carrier confinement, although improved optical confinement and reduced absorption losses may also play a role. The behavior ofJthatTMand the minimum inJthas a functiondare attributed to hole injection.

ISSN:0021-8979    

DOI:10.1063/1.1658314

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

High‐pressure experiments at 77°K indicate an axial pressure distribution in solid argon and methane for pressures in the range of 2.0–9.0 kbar. The normalized resistivities of a separated pair of bismuth crystals were measured as a function of pressure in a piston‐in‐cylinder apparatus using these solidified gases as the pressure transmitters. At an applied pressure of 8.0 kbar, average pressure gradients of 1.3 kbar per cm and 1.1 kbar per cm were measured for initial compressions of argon and methane respectively. Subsequent second and third compressions of these solids to 8.0 kbar reduced the average pressure gradient to 0.8 kbar per cm for both materials. The gradients in each solid were found to depend primarily on the applied pressure, and the increase of shear strength with pressure. Shear strength parameters were determined for each solid from an analysis of second and third compression data. The increase of shear strength with pressure was within 5% of that determined for argon of similar purity obtained by independent extrusion techniques, but was high when compared to methane of considerably higher purity.

ISSN:0021-8979    

DOI:10.1063/1.1658315

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The influence of fluctuations on microwave‐induced Josephson steps is treated phenomenologically and it is found that the center voltage of these steps is not shifted by the disturbance. Expressions governing the step shape are obtained for various noise spectra. The theory was checked by subjecting niobium point‐contact junctions to several forms of externally generated noise. The theory does not differentiate between internal and external noise sources, so that a number of the conclusions can be extended to intrinsic fluctuations.

ISSN:0021-8979    

DOI:10.1063/1.1658316

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A model of the energy transfer between Yb3+and Er3+in LaF3which explains the efficiency and time dependence of the conversion of infrared excitation to visible emission in this material is presented and analyzed. It is concluded that in La0.86Yb0.12Er0.02F3the probability of an excited Yb3+ion transfering its energy of excitation to an Er3+ion is at least an order‐of‐magnitude greater than the probability of the Yb3+ion decaying with the emission of radiation or phonons. Similarly, an Er3+excited to its4I11/2state is much more likely to lose the energy of excitation by radiationless energy transfer to a Yb3+ion than by other means. The decay time of the emission from the4S3/2state of the Er3+ion in La0.86Yb0.12Er0.02F3was measured to be 140±20 &mgr;sec if the Er ion is excited directly in the2H11/2or4F7/2states while the same emission decays with a time constant of 1.1 msec when the phosphor is excited with infrared absorbed by the Yb3+ions.

ISSN:0021-8979    

DOI:10.1063/1.1658317

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Thin films of cobalt were deposited on annealed CoO single crystal disks having surfaces parallel to (100) and (111) planes. The films were cooled to below the Ne´el temperature of CoO in a high magnetic field. The magnetization loop and the magnetic torque curves of the film deposited on the (111) plane of the CoO crystal, recorded below the Ne´el temperature of CoO, showed a unidirectional anisotropy due to the exchange interaction between the ferromagnetic film and the antiferromagnetic substrate. The anisotropy energy related to this coupling was found by two independent methods to be about 4×105erg/cm3. However, when the film surface was parallel to the (100) plane of the substrate only a slight coupling energy was detected.

ISSN:0021-8979    

DOI:10.1063/1.1658318

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A one‐dimensional model with four adjustable parameters is assumed for the Ne´el wall separating two oppositely magnetized domains in a thin ferromagnetic film. It yields an energy which is somewhat lower than in any of the published models. Its self‐consistency parameterSis not very sensitive to changes in the anisotropy constant; and, for the parameters usually used for Permalloy films, thisSvaries between 0.94 and 1.23, which is a necessary condition that the wall energy thus calculated is reasonably close to the true, three‐dimensional minimum. It turns out that almost the same results can be obtained by choosing convenient values for two of the four parameters, and adjusting only two.

ISSN:0021-8979    

DOI:10.1063/1.1658319

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Studies of the temperature dependence of the unidirectional anisotropy of permalloy films as a function of the oxidation of the surface are reported and correlated with electron diffration studies of the surface oxides. Hematite (&agr;‐Fe2O3) is found to correlate with the existence of the anisotropy in films oxidized at 120°C in which the transition temperature is near 40°K. A specimen oxidized at 250°C showed a higher and broader transition though no &agr;‐Fe2O3could be correlated with the existence of the unidirectional anisotropy.

ISSN:0021-8979    

DOI:10.1063/1.1658320

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Directional solidification of Au&sngbnd;Co eutectic produces an aligned array of fcc cobalt rods in a gold matrix. The cobalt becomes finer, but more lamellar, as growth rate increases. Intrinsic coercive force increases with increasing growth rate, reaching 330 Oe at 2.1×10−1cm/sec. Coercive forces up to 925 Oe are produced by subsequent wire drawing. Analysis of the magnetization curves indicates that deformation transforms the cobalt from fcc to hcp.

ISSN:0021-8979    

DOI:10.1063/1.1658321

出版商:AIP    

年代:1970

数据来源: AIP