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 series of low-voltage thyristor current switches based on (Al)GaAs/GaAs homo- and heterostructures with a volume charge region formed in the lightly doped p-GaAs base layer have been developed. The transient processes characteristics in pulse generation mode of nanosecond duration have been studied. It has been shown that the use of a wide-bandgap barrier based on AlGaAs at the n‑emitter/p-base junction allows reducing the minimum control current amplitude from 30 to 3 mA, and the turn-on delay time can be shortened to 6 ns. For the developed thyristor switches, a minimum transition time of 3.7–3.9 ns was demonstrated when operating in a circuit with a 1 nF capacitive load. In a circuit with a nominal 1 Ω resistive load, the thyristor switches provided a peak current of 17.5 A with a pulse duration of 3.7 ns.

The study investigates microstripe bars of optically isolated single-mode lasers based on heterostructures with double asymmetry, operating under sub-nanosecond current pulse pumping conditions. For microstripe bars with different filling densities of the emitting aperture, the effect of time delay dispersion of various stripes’ turn-on is demonstrated, with a maximum difference up to 50 ps. The developed microstripe bar designs demonstrate stable zero mode lasing. The microstripe bar consisting of 10 stripes with a 6 μm width and a stripe period of 20 μm demonstrates pulses with a peak power of 3 W and a duration of 140 ps under 0.4 ns current pulses pumping.

Radiative characteristics of microstripe laser diode bar in an external resonator based on an aspherical lens and a flat dielectric mirror were Investigated. The bar had total emitting aperture of 185 μm, formed by 10 stripes with a width of 6 μm separated by mesa-grooves. Operation in the external resonator of the entire emitting aperture was characterized by a multimode generation regime with a peak power of 3 W/6 A. Selection of lateral modal structures and transition to a single-mode regime is possible by limiting the number of stripes involved in optical feedback. Dependences of optical mode reconfiguration were studied by introducing limiting slits into the external cavity. It was shown that limiting the emitting aperture involved in the feedback to 65 μm allows us to demonstrate high-order single-mode operation with far-field divergence for the central lobe of 1°.

The main characteristics of 1550 nm few-mode laser diodes with aperture width $20 \mu \mathrm{m}$ and different cavity lengths (power, electrical, spectral and spatial characteristics) were measured. It is shown that there are two ranges of pump currents in which the characteristics of lasers behave differently: the first current range corresponds to operation in a low-mode mode, in which a scatter in the output characteristics of lasers is observed; in the second range the laser operates predictably and stably.

Laser diodes based on an asymmetric heterostructure AlGaAs/GaAs with a bulk active region, optimized for generating high-power subnanosecond optical pulses in the gain-switching mode, have been developed and investigated. The optimization of the asymmetric heterostructure design made it possible to obtain the parameter d/G = 4.2 µm (at the thickness d = 45 nm of the GaAs bulk active region and the optical confinement factor G = 1.08

AlzGa1−zAs layers of various compositions were grown using metalorganic chemical vapor deposition on a GaAs substrate with a pattern of alternating SiO2 mask/window stripes, each 100 µm wide. Microphotoluminescence maps and thickness profiles of AlzGa1−zAs layers that demonstrated the distribution of the growth rate and z in the window were experimentally studied. It was shown that the layer growth rate and the AlAs mole fraction increased continuously from the center to the edge of the window. It was experimentally shown that for a fixed growth time of 10 min, as z increased from 0 to 0.3, the layer thickness difference between the center of the window and the edge increased from 700 Å to 1100 Å, and the maximum change in z between the center of the window and the edge reached Δz 0.016, respectively. Within the framework of the vapor -phase diffusion model, simulations of the spatial distribution of the layer thickness and z across the window were carried out. It was shown that the simulation results were in good agreement with the experimental results for the effective diffusion length D/k: Ga—85 µm, Al—50 µm.

The study considers ridge waveguide characteristics in context of achieving maximum power and single-mode lasing. The watt-ampere and current-voltage characteristics, the spectrum, the radiation divergence along both axes depending on the pump current are measured, the dependences of the threshold current and differential efficiency vs the resonator length are plotted, the losses and the internal quantum yield are determined. Laser diodes with 2000 um resonator length showed the highest optical power – 190 mW at 375 mA pump current.

The possibilities for mode selection in mesa-stripe lateral waveguides for single-mode operation of lasers with a surface distributed Bragg reflector (DBR) are theoretically investigated. The dependence of the mode discrimination of the TE 00 and TE 01 lateral modes on the parameters of the laser crystal (mesa-stripe width, mesa-groove depth, and DBR depth) is analyzed. An algorithm for selection of these parameters depending on the required generation spectral width for a given design of heterostructure is demonstrated. A possibility for an increase in the width of the emitting aperture with maintaining of the single-mode lasing is shown. In this case, the selection of lateral modes in narrow mesa-stripe waveguides is achieved due to the difference in the DBR reflection coefficients for the TE 00 and TE 01 modes at a given DBR length. The resulting increase in the aperture can be used to increase the optical power of the laser in the single-mode regime.

The coupling coefficient for various geometric parameters of the surface DBR and ridge waveguide was calculated based on the coupled modes theory. The calculated reflection spectra of the DBR were obtained for various lateral modes depending on the width of the lateral waveguide. It is shown that the lateral modes selection is related to the optical confined factor of the two-dimensional TE mode distribution under the ridge. Selection is observed only for the last emerging mode, as long as it is weakly localized under the ridge. It allows to increase the width of the emitting area while maintaining the single-mode generation due to a significant difference in the DBR reflection for the fundamental and first lateral modes.