This study uses a numerical model to analyze the dynamics of high-power semiconductor lasers pumped by a high-repetition rate pulse sequence. It explores the distribution of photons and gain along the laser cavity and proposes an approach to optimize laser parameters for maximum efficiency and stability. The repetition rate range of interest spans from sub-MHz to several GHz.

A stability analysis of two modes of generation in semiconductor quantum well lasers is performed. These modes correspond to two solutions of the rate equations obtained by taking into account the internal optical loss that depends on the density of charge carriers injected into the laser waveguide region and, hence, on the injection current. It is shown that, in contrast to the first (“conventional”) mode of generation, which is always stable and hence observable, the second (“additional”) mode, which is entirely due to the internal loss that depends on the carrier density, is unstable and hence cannot be observed under the steady-state conditions in the laser structure considered in this work.

The operation of single-mode semiconductor (1060 nm) emitters microbar without optical coupling between the stripes was studied. The operation in the regime of a single relaxation optical pulse with a duration of 140 ps and power up to 3 W was demonstrated. The beam diagram of the microbar corresponded to the pattern of a single-mode emitter.

The main results of the studies on designing high-power semiconductor laser diodes based on asymmetric semiconductor heterostructures InGaAs(P)/Al(In)GaAs(P)/GaAs with low internal optical loss, whose concept was proposed at the Ioffe Institute, are described in detail. The basic technological approaches to designing highly strained active laser media for the spectral range up to 1100 nm are considered. The results of studying the cw high-power multimode semiconductor lasers, emitting in the wavelength ranges of 780–850, 900–980, and 1000–1100 nm; high-power pulsed semiconductor lasers; and high-power lasers with a very wide emitting aperture are considered. The key factors, determining the saturation of the output optical power of high-power semiconductor lasers, are determined.

The threshold conditions and operating efficiency of a semiconductor laser emitter with a large rectangular cavity (1 × 1 mm) based on an AlGaAs/GaAs/InGaAs heterostructure for high-power stripe lasers, which operate on high-Q internally circulating structures are estimated. Two designs of emitters with different characteristics of the laser-radiation propagation regions are proposed, and the possibility of achieving a differential efficiency that is characteristic of high-power stripe lasers (more than 70%) is shown.

The performance characteristics of semiconductor lasers based on quantum wells (QWs) are theoretically studied as functions of the thickness of the waveguide region [optical confinement layer (OCL)]. The maximum modal gain, optical-confinement factor (in QWs, OCLs, and emitters), threshold current density, electron and hole densities (in QWs and OCLs), internal optical loss (in QWs, OCLs, and cladding layers), internal differential quantum efficiency, currents of stimulated and spontaneous recombination and the output optical power of the laser are calculated as functions of the OCL thickness. It is shown that up to pump current densities of 50 kA/cm2 the dependence of the output power of the considered lasers on the OCL thickness is weak in the thickness range of 1.5–2.8 μm. This result is important for the development of high-brightness lasers, since such lasers use a wide waveguide to ensure low radiation divergence. It is shown that, at very high pump-current densities, the output power has a maximum as a function of the OCL width.

Possibility of tailoring the light-current characteristic (LCC) shape in quantum dot (QD) lasers by varying uniformity of QDs is discussed. Making the QD ensemble less uniform results in roll-over in the LCC. The second branch in the LCC appears with making the QD ensemble even less uniform.

Threshold conditions and efficiency analsis of a semiconductor laser emitter with a large (1x1mm) rectangular resonator based on AlGaAs/GaAs/ InGaAs heterostructures for high-power strip lasers operating on high-Q internally circulating structures is presented. Two designs of emitters with different laser radiation propagation region characteristics are proposed, and the possibility of differential efficiency characteristic as high as high-power broad lasers (70% and more) is demonstrated.

Operating characteristics of semiconductor quantum well (QW) lasers are theoretically studied in terms of the thickness of the waveguide region [optical confinement layer (OCL)]. We calculate the maximum modal gain, optical confinement factor (in QW, OCL, and cladding layers), threshold current density, electron and hole densities (in QW and OCL), internal optical loss (in QW, OCL, and cladding layers), internal differential quantum efficiency, stimulated and spontaneous recombination currents, and output optical power of the laser as functions of the OCL thickness. It is shown that up to the pump current density 50 kA/cm2 the output power of the considered lasers depends only slightly on the OCL thickness in the range of thicknesses 1.5–2.8 m. This result is important for designing high brightness lasers as broadened waveguides are used in such lasers to attain low beam divergence. At high pump current densities, the output power is shown to have a maximum as a function of the OCL thickness.

the results of modeling the laser generation controlled switching between high-Q closed mode structures in large rectangular cavities (up to 1x1mm) based on AlGaAs/InGaAs/GaAs heterostructures are presented. The model is based on rate equations. The basic principle of lasing switching is the controlled change in the internal optical loss due to the quantum-confined Stark effect)

The temperature behavior of operating characteristics in semiconductor lasers with a quantum-confined active region is studied with a proper account for (i) non-instantaneous capture of charge carriers from the waveguide region into the active region and (ii) internal optical loss that depends on the carrier densities. Because of (i), the carrier densities are not pinned in the lasing mode, i.e., they are functions of the injection current. In view of (ii) and as a result of pump-currentdependence of the carrier densities, so becomes the internal loss coefficient. This in turn leads to the roll-over of the light-current characteristic at high currents (i.e., decreasing optical power with increasing injection current) and, under certain conditions, appearance of the second branch in it. The laser characteristics are shown to transform qualitatively with varying temperature: they are conventional, i.e., consist of one branch, at low temperatures but they have two branches, i.e., are of a binary nature, at high temperatures. The two branches merge together at the maximum operating current beyond which the lasing quenches. In contrast to the first (conventional) lasing threshold, the threshold for emerging the second branch decreases with increasing temperature. The pump-current-dependence of the carrier densities and internal loss coefficient is also fascinating: these quantities decrease with increasing current in their second branches.

Abstract A lumped model of the dynamics of the controlled switching of high- Q closed-mode structures in rectangular large cavities (up to 1 × 1 mm and larger) based on AlGaAs/InGaAs/GaAs laser heterostructures is presented. The model considers the modulation of the useful power of a closed-mode structure due to controlled generation switching to an alternative closed mode. Generation-switching control between closed mode structures is implemented due to a variation in the optical loss of one structure. A variation in the optical loss occurs due to an increase in interband optical absorption due to the quantum-confined Stark effect upon the application of voltage to a laser crystal segment in the closed-mode propagation region.

A lumped model of the dynamics of the controlled switching of high- Q closed-mode structures in rectangular large cavities (up to 1 × 1 mm and larger) based on AlGaAs/InGaAs/GaAs laser heterostructures is presented. The model considers the modulation of the useful power of a closed-mode structure due to controlled generation switching to an alternative closed mode. Generation-switching control between closed mode structures is implemented due to a variation in the optical loss of one structure. A variation in the optical loss occurs due to an increase in interband optical absorption due to the quantum-confined Stark effect upon the application of voltage to a laser crystal segment in the closed-mode propagation region.

The work is devoted to the study of the formation features of high-quality closed modes based on total internal reflection effect in rectangular resonators of large (up to thousands wavelengths) size based on InGaAs/GaAs/AlGaAs laser heterostructures. Features of the spectral composition and spatial configurations of closed mode structures are experimentally investigated. The presence of frequency combs in the spectra was demonstrated and their correspondence to separate spatial configurations of closed modes was shown. The effect of a change in pumping and temperature on the mode composition is also considered.

This study is concerned with the specific features of how high-Q closed modes operating on the total-internal-reflection effect in large-size (up to hundreds or thousands of wavelengths) rectangular resonators based on InGaAs/GaAs/AlGaAs laser heterostructures are formed. The specific features of the spectral composition and spatial configurations of closed-mode configurations are experimentally examined. The presence of frequency combs in the spectra is demonstrated and their correspondence to the separate spatial configurations of closed modes is shown. The effect of changing the pumping level and the temperature on the mode composition of the emission is also considered.

The light-current characteristic (LCC) of semiconductor quantum well lasers is theoretically studied. It is discussed here that, due to internal optical absorption loss, which depends on the electron and hole densities in the optical confinement layer, (i) roll-over of the LCC occurs with increasing injection current, and, (ii) depending on the parameters of laser structures, the LCC can have two branches, i. e. the optical emission at two different output powers will be possible within a certain range of injection currents.

Threshold and power characteristics of quantum well lasers are theoretically studied in the presence of internal optical absorption loss. Due to variation of the internal loss coefficient with electron and densities in the optical confinement layer of the laser, the light-current characteristic may have two branches, each with its own threshold. The branches merge together at the maximum operating current.

Free carrier absorption in heterostructure layers of an operating laser diode has been measured. The proposed technique is based on coupling pulse probe light emission into the laser waveguide. Lasers with various heterostructure designs were measured at different current and temperature levels up to 30 kA/cm 2 and 85°C. The dependencies sufficiently describe the laser characteristics and can be used for heterostructure design comparison and optimization.

The operating characteristics of semiconductor quantum-well lasers, calculated with consideration for an increase in the internal optical loss in the waveguide region with increasing pump current, are presented. The condition of global electroneutrality in the structure is used. This condition consists in that the total charge of electrons in the 2D active region (quantum well) and bulk waveguide region (optical confinement layer) is equal to the total charge of holes in these two regions. Good agreement between the calculated and experimentally determined light–current characteristics is obtained.

Представлены результаты расчетов рабочих характеристик полупроводниковых лазеров на квантовых ямах с учетом роста внутренних оптических потерь в волноводной области с увеличением тока накачки. Использовано условие глобальной электронейтральности в структуре, которое заключается в равенстве суммарного заряда электронов в активной и волноводной областях суммарному заряду дырок в этих двух областях. Получено хорошее согласие измеренной и рассчитанной ватт-амперных характеристик. DOI: 10.21883/FTP.2017.07.44661.8522