Thermal resistivity of quaternary solid solutions InGaSbAs and GaAlSbAs lattice-matched to GaSb

Measurement of the thermal resistivity of the materials InGaSbAs and GaAlSbAs is reported. These materials have thermal resistivities of three to four times that of the GaSb substrate to which they were lattice matched. This makes them particularly suitable for use as the active medium in semiconductor light sources.<>     

Low-threshold current density InGaAsP/InP injection lasers with three-layer-waveguide double heterostructure (jth?0.5 kA/cm2 at 300 K)

Double heterostructure InGaAsP/InP lasers with a three-layer waveguide (or `separate-confinement? DH) have been prepared by the LPE method with a thin active layer. A decrease in threshold current density has been observed up to 512 A/cm2 in a four-sided cleaved diode at room temperature. CW operation of broad-area diodes is obtained in the pumping current range up to 2.5 A. Calculations of threshold current density for these laser structures are presented.     

A study of laser emission wavelength variations in 1.5 μmInGaAsP/InP BRS laser diodes: theoretical model and experiment

This is a study of the dependence of the emission wavelength on the cavity length observed in laser diodes with InGaAsP/InP buried ridge stripe (BRS) structure. Theoretical calculations were made taking into account the variation of the threshold gain due to the influence of the cavity length on the total optical loss and, therefore, on the level of the carrier density at the threshold. This density affects the spectral position of the gain peak thus creating the regular dependence of the emission wavelength on the cavity length. The band-shrinkage effect and the free carrier absorption effect are also considered. In samples covering the spectral range of 1.46-1.53 μm, the calculated and experimental results agree satisfactorily     

The treatment of middle-aged and elderly patients suffering from trochanteric fractures of the femur

Treatment of 198 elderly patients with trochanteric fractures included different conservative and operative therapy methods. For the first time in Russia a new approach of extrafocus osteosynthesis was recommended for "decompensated" patients. It is proved, that for this category of the injured, active surgery tactics results in a considerable improvement of treatment outcome.     

Anomalous dispersion, differential gain, and dispersion of the α-factor in InGaAs/AlGaAs/GaAs strained quantum-well semiconductor lasers

A new procedure for the experimental determination of the differential gain and dispersion of the amplitude-phase coupling coefficient in semiconductor injection lasers was proposed and implemented. The α-factor and differential gain for InGaAs/AlGaAs/GaAs single quantum well (QW) semiconductor lasers were determined using this procedure in a wide spectral range (from 957 to 996 nm) at various pumping current densities (from 280 to 850 A/cm²). The factor which characterizes the dispersion of the group velocity and restricts the minimum duration of the lasing pulse at the level of 10^?13 s was experimentally determined for InGaAs lasers for the first time.     

Refractive indices of wurtzite and zincblende GaN

Refractive index measurements on both wurtzite and zincblende GaN films grown by plasma-enhanced molecular beam epitaxy are reported. For birefringent uniaxial wurtzite GaN samples the index of refraction was measured along the crystalline axis. In this direction the index is 2.78 at 3.4 eV. For cubic GaN films grown on GaAs substrates, the refractive index is 2.91 at 3.2 eV. Estimation of the confinement factor for optimised waveguides based a combination of III-V nitrides indicates very favourable values for laser operation.<>     

Properties of ion-implanted high-power angled-grating distributed-feedback lasers

An improvement of the linearity of the light-current characteristics and the beam quality of high-power /spl alpha/-distributed feedback lasers is achieved by an ion implantation of the regions outside the contact stripe. The linear part of the light-current characteristics of 4-mm-long devices emitting at 1060 nm is extended to P=1.8 W output power. The times-diffraction-limit factor M/sup 2/ remains constant, equal to 1.7 over the whole power range. Simulations of the electro-optical behavior reveal that the improvement is achieved by a suppression of optical field components which propagate inside the cavity perpendicular to the facets.     

Modeling and measurements of the radiative characteristics of high-power /spl alpha/-DFB lasers

A new above-threshold model of /spl alpha/-DFB lasers is presented. It is based on a generalized beam-propagation method and takes into account spatial hole burning and self-heating effects. Up to moderate output powers, a good agreement between simulated and measured radiative characteristics is obtained. The theoretical model was used to design an optimized laser structure with a 4-mm-long cavity, which yielded a maximum output power of 3 W with a times-diffraction-limit factor of M/sup 2//spl ap/3.