摘要:

An XeCl excimer laser was operated at the high repetition rate of 2.5 kHz, which can circulate the laser gas uniformly and efficiently. The characteristics of the gas flow rate and the average laser power versus the repetition rate were investigated in both He and Ne buffer gas mixtures. In He buffer gas, the average laser power saturates at 1.3 kHz and, thereafter, drops abruptly. On the other hand, stable operation at the highest repetition rate, 2.5 kHz, has been attained in Ne buffer at a gas flow rate of 54 m/s with an average laser power of 87 W.

ISSN:0021-8979    

DOI:10.1063/1.346922

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The facet temperature of AlGaAs single‐quantum‐well laser diodes were examined via Raman microprobe spectroscopy. The facets were fabricated either by cleaving in air or by chemically assisted ion‐beam etching. The ridge width was 5 &mgr;m. Large sample‐dependent variations in the heating induced by the argon probe beam are observed. These variations correlate with the appearance of disorder‐induced modes in the Raman spectrum and the bias current‐induced heating of the laser facet.

ISSN:0021-8979    

DOI:10.1063/1.346923

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The superconducting transition temperature of lead has been reexamined as a function of pressure to 17 GPa (170 kbars).Tc(P) determined with helium as the pressure medium differed from that when 4:1 methanol:ethanol was used. The disagreement is particularly net in the fcc phase and can be ascribed to a sensitivity ofTcto the state of shear stress. This implies thatTc(P) for Pb is unsuitable as a manometer. The possibility that the hcp phase, occurring above about 14 GPa, may be useful as a manometer is discussed, but a definite conclusion cannot be reached at the present time.

ISSN:0021-8979    

DOI:10.1063/1.346924

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

GaSb lattice‐matched Ga1−xInxAsySb1−yhas been grown by liquid phase epitaxy on (100) and (111)B oriented substrates using initial melt supersaturation &Dgr;Tvarying from 10 to 30 °C, at growth temperatures >600 °C. It is shown that the band‐gap cutoff wavelength, measured at room temperature by the electroreflectance method, is ∼2.38 &mgr;m for (100) layers whatever &Dgr;T, and increases from 2.38 &mgr;m up to 2.51 &mgr;m for (111)B oriented layers when &Dgr;Tis increased from 15 to 25 °C. Photoluminescence experiments at 2 K confirm the band‐gap reduction occurring at high &Dgr;Twith the (111)B orientation.

ISSN:0021-8979    

DOI:10.1063/1.346925

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Pellets of bulk density 5.5 g/cm3,Tcof 107 K, and magnetic critical current of 104A/cm2(77 K, 3×4×10 mm3) were achieved under the multiple pressing and sintering process in the Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Oxbulk samples. The powder x‐ray diffraction shows the existence of the single high‐Tcphase. Highly textured microstructures with strong (001) reflections were confirmed by x‐ray diffraction on the surface of the pellets. The internal textured microstructures were obviously observed by a scanning electron microscope. No second stage was observed, and the superconducting volume fractions of the Meissner and shielding effects were more than 70% and 90%, respectively, as observed by dc magnetic susceptibility.

ISSN:0021-8979    

DOI:10.1063/1.346926

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Diamond crystallites were synthesized using various oxygen‐hydrocarbon flames. The flames have been profiled in real time using a nonintrusive diagnostic technique. Optical emission spectra for different zones have been recorded and the active species identified. Diamond growth was observed only in the thermodynamically unequilibriated primary combustion zone of the flames. Carbon‐bearing species, atomic hydrogen, and atomic oxygen, noted to be critical for diamond growth, were observed in the flames. The diamond growth was confirmed by x‐ray diffraction, laser‐Raman analysis, and scanning electron microscopy. The study offers the first insight into the flame spectra in the context of diamond synthesis at atmospheric pressures.

ISSN:0021-8979    

DOI:10.1063/1.346927

出版商:AIP    

年代:1990

数据来源: AIP