摘要:

The Lorentz and Ampere laws are shown to be equivalent in magnetostatics. Both predict equal and opposite forces on complementary parts of a current distribution, and only a normal force on a current element. There is no force along the element. The illusory differences between the two are attributed to the incorrect integration of the differential forms of the laws, and to the inappropriate use of line current elements as sources, instead of surface or volume elements.

ISSN:0021-8979    

DOI:10.1063/1.334448

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A very sensitive method for detection of surface defects is presented. This technique relies on the utilization of good quality focused surface ultrasonic sources. Experimental results on ceramic samples with artificial defects are reported. Using this method, a precise positioning and dimensioning of the defects may be performed.

ISSN:0021-8979    

DOI:10.1063/1.335469

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Nb3Ge thin‐film microbridges are fabricated on a cylindrical substrate to form rf SQUIDs. High temperature operations well above 10 K (up to 17.5 K) are obtained. An intrinsic flux noise of the order of 10−4&Fgr;0/(Hz)1/2is estimated from the step rise parameter. Comparison with a theoretical noise indicates a nonsinusoidal current phase relation of the microbridge.

ISSN:0021-8979    

DOI:10.1063/1.334449

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The change in the electronic contribution to the elastic constants of Nb due to hydrogen impurity has been evaluated using a distance‐dependent tight‐binding parametrization scheme. The good agreement between the calculated results and the experimental data clearly demonstrates that the positive change ofC44observed in niobium with hydrogen impurity originates from the electronic contribution.

ISSN:0021-8979    

DOI:10.1063/1.334450

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Correlation between intensity noise and fine structures of longitudinal modes in a semiconductor laser coupled to an external cavity has been investigated. It is experimentally shown that the intensity noise is perfectly suppressed when the laser oscillates in ‘‘pure’’ single frequency oscillation even with strong optical feedback. Intensity noise, which arises only when several external cavity modes exist, is interpreted in terms of the time‐dependent refractive index in the semiconductor cavity caused by the light beatings among the lasing modes.

ISSN:0021-8979    

DOI:10.1063/1.334451

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Electrostatic double‐probe measurements of the electron temperatureTe, in rf excited laser discharge mixtures of CO2/N2/He to which Xe is added, reveal that the addition of Xe causesTeto be lowered. A possible mechanism for the beneficial effect of xenon on the operation of CO2lasers is briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.334452

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We describe InGaAsP inverted rib waveguide lasers emitting at 1.54 &mgr;m with pulsed current thresholds as low as 60 mA, external quantum efficiencies of up to 0.2 per facet, and emitting 16 mW in the lowest order. Pulsed operation to 110 °C withT0values of 50–72 °C were obtained. For continuous operation at 15 °C up to 21 mW per facet was observed with external quantum efficiencies of 0.15 per facet andT0up to 62 °C. The maximum continuous operating temperature was 55 °C and was determined by heating of the junction.

ISSN:0021-8979    

DOI:10.1063/1.334453

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Continuously tunable laser sidebands have been generated by mixing radiation from an optically pumped far infrared (FIR) molecular laser, operated at 693, 762, 1627, and 1839 GHz, with that from millimeter‐wave klystrons in a Schottky‐barrier diode. An enhancement in conversion efficiency over similar systems reported previously is obtained by using a Michelson interferometer to separate the sidebands from the carrier and by placing the Schottky diode in an open structure corner cube mount. With 4 mW of laser power at 693 and 762 GHz the sideband power was measured to be 3.0 &mgr;W. This is at least an order of magnitude better than the previously reported results. At higher frequencies, 22 mW of 1627‐GHz laser power produced about 2.5 &mgr;W of sideband output, while 3mW of 1839‐GHz laser power generated about 100 nW of sideband radiation. The lower efficiency at the higher frequencies is due primarily to the mismatch between the laser radiation and the fixed‐length diode antenna. To demonstrate the tunability of the generated far‐infrared radiation, the laser sidebands were swept through absorption lines of HDO and H2CO near 600 and 800 GHz. The absorption signals were easily seen, using either video or lock‐in detection techniques.

ISSN:0021-8979    

DOI:10.1063/1.334454

出版商:AIP    

年代:1985

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.335507

出版商:AIP    

年代:1985

数据来源: AIP