摘要:

Optically pumped near ultraviolet lasing from single‐crystal GaN grown by metalorganic chemical vapor deposition has been achieved over a temperature range from 10 K to over 375 K by using a side‐pumping geometry on small barlike samples. The laser emission threshold was measured as a function of temperature and the threshold was found to show weak temperature dependence: ∼500 kW/cm2at 10 K and ∼800 kW/cm2at room temperature (295 K) for one particular sample studied. The longitudinal lasing modes were clearly observed. The characteristics of the temperature dependence of the laser emission threshold suggests that GaN is a suitable material for the development of optoelectronic devices required to operate at high temperatures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114222

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An intersubband electroluminescent light source in the 8–13 &mgr;m spectral region is reported. The structure was grown by molecular beam epitaxy in the lattice matched AlInAs/GaInAs material system and consists of coupled‐quantum‐well active regions alternated with compositionally graded electron injecting regions. The device operates in the temperature range from 10 to 200 K with measured integrated optical powers up to 6 nW. The peak of the electroluminescent spectrum blue shifts linearly with current due to the Stark effect. From these data and straightforward electrostatic considerations we obtain the intersubband nonradiative electron lifetime, in good agreement with the calculations. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114179

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Above‐threshold analysis of antiresonant reflecting optical waveguide (ARROW) diode lasers has been performed. One key finding is that preferential pumping of the (central) low‐index core region dramatically enhances the device single‐mode power capability, as a result of defocusing and subsequent radiation‐loss increase for the first‐order spatial mode. Stable, single‐mode operation to drive levels ≳10× threshold is predicted for 6‐&mgr;m wide core devices, in excellent agreement with experiment. Similar performance is found to hold true for ARROW devices with cores as wide as 10 &mgr;m, although due to gain spatial hole burning, the far‐field beam pattern experiences mild broadening. Study of triple‐core ARROW structures of 20‐&mgr;m‐wide aperture shows stable fundamental‐mode operation to ≳10× threshold, thus raising the prospect for stable, single‐mode reliable operation to power levels as high as 1 W cw. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114152

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We describe the generation of terahertz radiation by optical rectification in an electro‐optic crystal mosaic. The mosaic is constructed from four single crystals of the organic salt dimethyl amino 4‐N‐methylstilbazolium tosylate and is approximately 1 cm2in area. We characterize both the optical rectification efficiency and the spatial and temporal profiles of the generated terahertz beam, and find that the mosaic performs as well as a single crystal. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114162

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A periodically domain‐inverted KTiOPO4crystal has been characterized for the first time by multiple‐crystal multiple‐reflection x‐ray topography. The striation contrast within the domain‐ inverted regions has been revealed in high strain‐sensitivity reflection topographs. The origin of formation of the striation contrast and the mechanism of domain inversion in KTiOPO4are discussed in terms of the structural characteristics of KTiOPO4. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114165

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The nucleation of diamond on the amorphous SiO2mirror surface has been achieved by means of adding an ac signal to the negative dc bias in the microwave plasma chemical vapor deposition. It is found in experiment that the nucleation of diamond happens only after the frequency of the ac signal exceeds a threshold. The results also show that the diamond nucleation density depends not only on the ac frequency but also on the magnitudes of the ac signal and the dc bias. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114166

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nanocomposite Ni/Al2O3films have been produced by electrochemical deposition where 50 and 300 nm Al2O3particles are dispersed in a nickel matrix. These films exhibit considerable enhancements in their hardness in comparison to pure nickel. The strengthening mechanism is explained in terms of an Orowan bowing hardening mechanism and, hence, related to the volume fraction of the reinforcing phase. These films may have application as strong coatings that retain many of the physical properties (e.g., optical, thermal, electrical) of the metal. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114167

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The stress transfer behavior in multilayer thin film structures (nickel/polyimide/copper) was measured using x‐ray stress analysis. Copper was deposited in various line lengths, and the stress/strain transferred from a loaded Ni substrate to the Cu thin film was measured as a function of line length. It was found that there is incomplete strain transfer from one layer to another, and that the shape of the stress transfer function is similar to that predicted by the shear lag model. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114168

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A reflection electron energy loss spectroscopy system has been developed to investigate local surface atomic structures around light elements such as C, N, and O. Electrons scattered inelastically on a surface with a small scattering angle are energy analyzed. This system was used to measure energy loss near‐edge structures (ELNESs) for materials such as BN, graphite, and NiO. The comparison between ELNES and x‐ray absorption near edge structure suggests that the ELNES is useful for the atomic structure analyses of surfaces. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114169

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Leakage currents in epitaxial ferroelectric/perovskite‐conductor heterostructures reproducibly show diode properties having hysteresis. The hysteresis appears in forward bias, which is positive for electron (n) type conductors and negative for hole (p) type conductors. The hysteresis is due to the increase of conductivity by the forward bias current, which exhibits the memory retention for more than an hour. The write and erase speeds of the diode and the origin of the effect are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114170

出版商:AIP    

年代:1995

数据来源: AIP