Degradation of cw injection heterolasers

A model is presented of the parametric degradation of cw heterolasers. It permits an estimate of the parameter variation due to aging and to irradiation by a fast-particle current. The model takes the initial conditions and a failure criterion into account, and permits calculation of the operating lifetime under adjustable pumping as well as under various lasing-power levels. The most promising quality-control measures are considered.Translated from Preprint No. 139 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Difference-frequency pulse generation in quantum well heterolasers

It is shown that mid-to far-infrared (IR) and terahertz (THz) pulse generation via difference-frequency mixing in quantum well (QW) dual-wavelength heterolasers can be rather efficient under the modelocking regime for one or both lasing fields even at room temperature. In such a device, the long-wavelength field is produced in the process of intracavity difference-frequency mixing of two optical fields: continuous wave (CW) and pulsed (or both pulsed), due to the resonant intersubband quantum coherence in QWs, as well as due to the nonresonant second-order semiconductor bulk nonlinearity. The mode-locking regime of the optical generation allows one to significantly enhance the pulsed driving fields in comparison with those under CW operation and, therefore, substantially increase the output difference-frequency power. Within a simple model, an explicit formula for the intensity and shape of the generated IR or THz pulse is derived. It is shown that this method is capable of producing picosecond pulses at a ∼ 1-GHz repetition rate with a peak power of the order of 1 W and ≲0.2 mW at 10 and 50 μm wavelengths, respectively. Original Text ? Astro, Ltd., 2007.     

Influence of photon transport on diffusion processes in stripe heterolasers

The influence of photon transport on the diffusion of nonequilibrium charge carriers in heterolasers with stripe contact and in structures with a transverse p-n junction arrangement is taken into account. Results are presented of a machine computation of the nonequilibrium charge carrier (NCC) concentration profile and the radiation density in the active layer of AlGaAs lasers in the prethreshold pumping mode.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 12–17, June, 1984.     

Properties of electrically active structural defects in crystalline semiconductors

The internal structures, composite elements, electrophysical properties, and characteristic parameters of impurity clouds, noise supertraps, disordered domains, and stacking defects are compared in crystalline semiconductors. It is shown that the mentioned macrodefects possess common properties: They have a nucleus and an impurity atmosphere, are separated by a potential barrier, are shaped with the participation of Frenkel defects and oxygen ions, have a threshold inclusion, sharply increase the rate of charge carrier generation-recombination as the electrical field grows, etc. It is noted that current channels in non-crystalline semiconductors are characterized by properties close to these after they have been formed. It is assumed that the electrical activity of the structural macrodefects in crystalline semiconductors may be related to the fundamental properties of noncrystalline semiconductors (for instance, the resistance switching effect). Domains adjoining a macrodefect and destroyed by it visibly manifest these properties.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 95–100, April, 1988.     

Collective overcoming of point defects by dislocations in the dynamic region

A mechanism of collective overcoming of point defects by dislocations during the over-barrier slip has been proposed. It has been shown that the interaction between dislocations promotes the overcoming of point defects at a high dislocation density.     

Enhancement of the Faraday rotation in magnetically active periodic structures with defects

Relations that determine the field of a light wave transmitted through and reflected from a periodic structure lying on a substrate and containing a defect layer are derived for the case of an arbitrary symmetry of both the defect layer and the layers forming the structure. Exact expressions are obtained for the determination of the positions of the defect modes. The feasibility of a considerable enhancement of the Faraday rotation while retaining 100% transmission through the defect-containing magnetically active structure at a high dielectric contrast is revealed. It is shown that the angle of magnetooptical rotation of the polarization plane in a periodic structure is a bounded quantity.     

Investigation of the total conductivity of heterolasers with a strip contact with reverse bias

The electrical properties of DGS lasers with a strip contact on the basis of Al_xGa_1–xAs with reverse bias, including the breakdown domain, are investigated experimentally. It is shown that the dependence of the barrier capacitance on the voltage is described well by the relationship C_b = C_o/(1– V/V_k)^1/m, where C_o = (50–110) pF and m = 2.0–2.7. The capacitance for zero bias C_o depends weakly on the frequency in the range 660 kHz–60 MHz. The active conductivity for V = 0 increases by approximately an order as the frequency changes from 15–60 MHz. The dependence of the active and reactive components of the total laser conductivity on the current is investigated at fixed frequencies in the range mentioned. The weak dependence of the reactive component on the current is noted in the breakdown regime associated with stabilization of the reverse voltage on the laser. Possible physical mechanisms responsible for the kind of characteristics obtained are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 52–56, November, 1983.     

Structural defects in Ni-Ti alloys in the region of B2-phase homogeneity

A comparison is made of the x-ray and pycnometric densities of Ti-Ni alloys, with a high nickel content relative to the equiatomic composition, when the alloys are quenched outside the region of -phase homogeneity. An analysis is made of the possibility of the formation of vacancies, interstitial atoms, triple defects, and substitutional defects in the alloys. It is concluded that substitutional defects are formed: nickel atoms which are excess atoms relative to those found at the lattice points in the CsCl superstructure are located in the titanium sublattice. An evaluation showed that in the formation of alloys near the equiatomic composition of TiNi, the atomic volumes of titanium and nickel are about 1.8 and 7.4% smaller than for the pure components, respectively.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 45–50, November, 1987.     

Mode locking and efficient generation of pulsed difference-frequency radiation in two-color heterolasers

Efficient schemes are proposed for generation of picosecond pulses in the mid/far-IR and THz ranges through intracavity nonlinear mixing of fields generated in two-color injection heterolasers, operating in the mode-locking regime at room temperature. It is shown that these schemes make it possible to increase the peak lasing power by a factor of about 100.     

Acceptor resonances and electrically active point defects in α-Sn

New galvanomagnetic and thermoelectric results for electron-irradiated n-type α-Sn show that acceptor resonance states in the conduction band play a crucial role. It is found that these states are near the band edge and are associated with electrically active point defects resulting from atomic displacements.     

The rotation of the polarization plane of quantum-well heterolasers emission under the ultrasonic strain

The paper is devoted to an acousto-electron effect in the nanodimensional laser heterostructures. The effect results in a modulation of the laser emission intensity as well as in a turn of the emission polarization by the sound strain. Theoretical treatment of the experimental data is presented.