摘要:

A detailed study on the optical quality of atmospheric pressure metalorganic vapor phase epitaxy grownGaAs(1−x)Nxepilayers (on GaAs substrates) in which the N incorporation is accomplished using dimethylhydrazine precursor is reported. We show here that the poor optical quality of these as-grown layers can be significantly improved by carefully planned post-growth heat treatments. Optical data are presented to demonstrate unambiguously that such treatments affect in no way the physical properties of these metastable layers (no phase separation) and that the improvement of their optical quality is closely connected to the incorporation behavior of N in this growth method. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120579

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Carbon nitride films were produced by simultaneous irradiation of well-defined hyperthermal (50–400 eV), isotopically mass-separated12C2−and14N+ions with various kinetic energy combinations. It was found that the intensity of CN-triple bonds normalized by the amount of nitrogen atoms in the films and the complex refraction index(n,k)are correlated with the energy combination of12C2−and14N+ions. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120580

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Thin films of BaFCl:Eu with photostimulable luminescence (PSL) were grown by vapor deposition. For substrate temperatures at or below 350 °C, films were optically transparent and exhibited higher resolution in x-ray imaging than a commercial, particulate PSL phosphor screen, when luminescence was stimulated by scanning with a focused HeNe laser. Although post annealing films in a hydrogen atmosphere at 600–900 °C increased their PSL signal, which was relatively weak in as-deposited films, annealing reduced imaging resolution, apparently because of an increase in optical scattering of the focused laser. The implications of hydrogen annealing for the PSL mechanism are also discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120581

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated spectroscopically the gain characteristics of InGaN quantum well (QW) diode lasers. While the transparency condition can be reached at a moderate current density, the filling of localized band-edge states is a prerequisite for achieving lasing in this profoundly nonrandom alloy. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120607

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

GaAs/AlAs pillar microcavities with elliptical cross section have been fabricated by molecular beam epitaxy, electron-beam lithography, and reactive ion etching. We study their lowest energy confined photonic modes by photoluminescence, using a quantum box array placed inside the cavity as an internal broadband light source. Such an anisotropic cross section allows to split the twofold polarization degenerate fundamental mode of circular micropillars into a pair of orthogonal linearly polarized modes. Their energy splitting, which is well accounted for by a simple perturbative model, is studied experimentally and theoretically as a function of the eccentricity and average radius of the pillars. Splittings as large as 15 meV are observed, which is very encouraging for applications ranging from the improvement of the polarization locking in vertical cavity lasers to the fabrication of light emitting diodes with a better control of the spontaneous emission. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120582

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We calculate the temperature dependence of the threshold current densityJthin optimized (minimalJth) and unoptimized InAs/InGaSb superlattices. We find that the threshold current density of the unoptimized superlattice is well described byJth∝eT/T0,withT0∼32 Kfrom 25 to 275 K. This is the first microscopic calculation for these superlattices which indicates thatJthis well described by an empirical exponential form. In contrast, the threshold current density of the optimized superlattice is not well parametrized by a characteristic temperatureT0.This superlattice is only optimized between 250 and 350 K, due to the sharp structure of the intersubband absorption spectrum. We also consider the effect onJthof uncertainties in layer thicknesses. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120583

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate a new experimental method which allows the measurement of the nonlinear optic index in absorptive media with great sensitivity. In this technique the reflection from a polarized Gaussian laser beam close to the Brewster angle is measured. A sensitivity enhancement factor of 30 with respect to other techniques is observed for an optical crystal, and higher values are possible to be obtained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120584

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

High performance index-coupled quantum cascade distributed feedback (QC-DFB) lasers operating at&lgr;≈8.5 &mgr;mare reported. Reliable dynamic single-mode emission with a side mode suppression ratio⩾30 dBis obtained. The continuous single-mode tuning range is 140 nm. In pulsed operation a record high peak output power of 60 mW at 300 K is achieved. We further report on the first continuous-wave QC-DFB lasers. These devices display an output power of 10 mW at 120 K.

ISSN:0003-6951    

DOI:10.1063/1.120585

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the observation of highly efficient laser emission from a single InAs layer with an effective thickness of 1.5 monolayers (ML) embedded in bulklike GaAs. Lasing action is obtained at the wavelength of the InAs thin-layer luminescence (870 nm) by cw optical pumping with a threshold power density of0.9(3) kW/cm2at 10 K. Gain measurements yield a very high material gain of1.0(5)×104 cm−1for the InAs layer when pumped with∼10 kW/cm2at low temperatures. The 0 dimensional character of the emission as determined from cathodoluminescence and the absence of band-gap renormalization with increasing pump level speak for an excitonic mechanism of population inversion. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120586

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report high power cw operation of a slab waveguide atomic xenon laser in a spectral region of low atmospheric absorption. Using transverse radio frequency discharge excitation at 49 MHz and a hybrid waveguide-unstable resonator, with a sharp band edge on the reflectivity versus wavelength curve of the laser mirrors, 50 mW was obtained on the 3.869 &mgr;m transition and 210 mW on the 3.895 &mgr;m line. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120587

出版商:AIP    

年代:1998

数据来源: AIP