摘要:

Photostimulated luminescence phenomenon was observed in a fluoroaluminate glass doped withEu2+.When the x-ray irradiated glass was excited by a He–Ne laser (633 nm), photostimulated luminescence at 400 nm due to the5d–4ftransition ofEu2+ions was observed. X-ray absorption spectra showed that a part ofEu2+converted toEu3+upon the irradiation of x-ray. By comparing with the investigations on photostimulable luminescence phosphorBaFBr:Eu2+,the luminescence appears to result from the photostimulated recombination of holes and electrons at traps, which leave electrons in a long-lived excited state. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119637

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A five-wavelength surface emitting laser diode array based on surface mode emission is reported. The wavelength control is achieved by postgrowth adjustment of the surface structure. Wavelength spacing between laser groups is 1.1 nm in average and the wavelength reproducibility is±0.13 nm.The total change in the emission wavelength over the array is 4.78 nm. The single array elements show single mode emission with a full width at half-maximum of 0.08 nm in average and a side mode suppression ratio up to 20 dB. This type of laser diode is of high interest for wavelength division multiplexing applications. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119638

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report a multiple quantum well ridge guide laser tuned by the quantum confined Stark effect. In contrast to carrier-induced effect tuned lasers, the frequency modulation response of our laser is highly uniform(±0.7 dB)over the frequency range from 10 kHz to 100 MHz, and within±2.5 dBfrom 5 kHz to 500 MHz, with the upper frequency parasitic capacitance limited. We predict that the response could be extended to over 20 GHz by using a low parasitic contacting structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119639

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Carrier distribution in multiple quantum well (MQW) lasers is studied by measuring laser wavelength. The MQW is designed to contain wells with different thicknesses. The MQW laser wavelength agreed with the transition wavelength of the wells near thep-clad layer at room temperature. At low temperatures, however, the laser wavelength corresponded to the thicker wells. The results imply that hole localization takes place at room temperature but disappears at low temperatures. This shows the invalidity of the conventional capture/escape model. The importance of the mean free path of unbound carriers is pointed out. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119640

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The two lowest singlet excited states of divalent Si defects in silicate glasses are studied byab initiomethods. Excitation energies of 5.2 and 6.8 eV are obtained. Steady convergence to these values is shown with the increase in size both of the model cluster and of the basis set employed in the calculations. The results clearly demonstrate the viability of the quantum-chemical cluster approach for the study of local excitations in glass defects. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120422

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated the electron heating in metallic diffusive wires of varying length at liquid-helium temperature by measuring the electric noise. The local increase of the electron temperature can be essential already for small currents and is well described by a heat-diffusion equation for the electrons. Depending on the electron thermal conductance and the electron–phonon coupling in the wire, different length regimes are identified. The quantitative knowledge of the electron temperature is important for analysis of nonequilibrium effects involving current heating in mesoscopic wires. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119641

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An innovative compliant GaAs substrate was formed by wafer bonding a 30 Å GaAs layer to a bulk GaAs crystal with a large angular misalignment inserted about their common normals. InSb epitaxial layers, which is about 15&percent; lattice mismatched to GaAs, have been grown on both compliant substrates and conventional GaAs substrates. Transmission electron microscopy studies showed that the InSb films grown on the compliant substrates have no measurable threading dislocations, whereas the InSb films on the conventional GaAs substrates exhibited dislocation densities as high as1011 cm−2.The observations made here suggest that the defect-free heteroepitaxial growth of exceedingly large lattice-mismatched crystals can be achieved with compliant universal substrates. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119642

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The essential features of the stress overshoot in the stress-strain curves ofZr65Al10Ni10Cu15(at. &percent;) metallic glass that has a wide supercooled liquid region were revealed. The stress overshoot was dependent on temperature, strain rate, and stress relaxation. During the stretch, a change in strain rate gave rise to stress overshoot or undershoot which was sensitive to the variable quantities in the strain rate. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119643

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The synthesis of copper oxycarbonate superlattices comprised of two structural types that are observed in highTcsuperconductors was achieved using the pulsed laser deposition (PLD) technique. These artificially layered materials consist of specific numbers of alternately stacked infinite layerSrCuO2and oxycarbonateBa2−xCaxCuO2CO3blocks, and were grown on (110)NdGaO3using two targets. From x-ray diffraction, it was found that several unit cells ofSrCuO2could be inserted between the layers ofBa2−xCaxCuO2CO3. These results demonstrate that a large series of new structures combining oxycarbonate with oxide components can be obtained using a multitarget PLD system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119644

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A unique growth mode of Ge on Si(110) substrates was clarified by photoluminescence (PL) spectroscopy. A spectral redshift and an increase of the relative no-phonon intensity were found for PL from the two-dimensional Ge layer on Si(110) compared to that on Si(100). These results likely arise from nonuniformity in the Ge layer thickness owing to the step-bunched Si(110) surface and resultant exciton localization. The two-dimensional to three-dimensional growth mode changeover was observed as evidenced by emergence of broad PL from Ge islands. In contrast to Ge on Si(100) PL from the wetting layer was found to show continuous redshift with increasing Ge coverage even after Ge island formation. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119645

出版商:AIP    

年代:1997

数据来源: AIP