The generation of high-power laser pulses using a compact hetero-integrated assembly based on a semiconductor laser with a dual-element composite 2 mu m x 100 mu m aperture and a compact heterothyristor switch is demonstrated. The achieved peak optical power was 33 W with a pulse duration of 3 ns at a thyristor operating voltage of 55 V. The leading edge of the laser pulse turn-on was 50 ps to a power level of 24.7 W, and the turn-on delay between the elements of the composite aperture was 160 ps.

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.

Broad-arealasers with a $100 \ \mu \mathrm{m}$ aperture based on heterostructures with double asymmetry and active regions at wavelengths of 850 nm using bulk 45 nm GaAs and at 970 nm using quantum wells were investigated. Output optical powers in the single first relaxation peak regime from 12 to 22 W were achieved with pulse durations from 100 to 150 ps.

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°.

Photoactivated current switches for pumping diode laser stacks with ns and sub-ns current pulses are studied. Test optical pulse: 860 nm, 50 ps leading edge, peak power up to 9.3 W. Samples were tested at up to 50 V bias. Photoresponse amplitude was up to 17 V (340 mA) with linear dependence on pulse power. Photoresponse leading edge duration was ~80 ps (20-80% level).

Measurements of the output optical power, laser-oscillation spectra, optical-pulse duration, and switching-on delays of semiconductor lasers–thyristors with a strip width of 200 μm and a length of 980 μm were performed in the operating temperature range from 20 to 70°C at a nominal value of the discharge capacitor of 22 nF and a control-current amplitude of 10.4 mA. It is shown that lasers–thyristors have high temperature stability. When the devices were heated from 20 to 70°C, the level of reduction of the peak output power did not exceed 15

shalygin@rphf.spbstu.ru Abstract. Comprehensive studies of the luminescence of p - i - n structures with 10 compensated GaAs/AlGaAs quantum wells have been performed. The studies were carried out in the terahertz (THz) and near -infrared (NIR) spectral ranges with both optical and electrical pumping of nonequilibrium charge carriers. The THz photoluminescence spectra revealed an emission line caused by electron transitions from the first size -quantization subband e 1 to the ground levels of donors D 1 s . The photo- and electroluminescence spectra in the NIR range revealed an emission line caused by electron transitions from the D 1 s levels to the first subband of heavy holes hh 1. These transitions provide effective depletion of the D 1 s levels and are therefore relevant for creating a THz emitter operating at e 1- D 1 s transitions. At high injection currents in the p - i - n diode, lasing occurs at the D 1 s - hh 1 transitions, which increases the efficiency of depletion of the D 1 s levels. It is shown that for a given optical pump power or injection current density, the overall rate of the D 1 s - hh 1 transitions in the p - i - n structure with 10 QWs is significantly higher than in similar structure with 50 QWs.

Photo- and electroluminescence in p–i–n structures with compensated GaAs/AlGaAs quantum wells have been studied. Two structures with different doping profiles were studied: with spatial separation of donors and acceptors (donors are localized in quantum wells, while acceptors are localized in barriers) and without it (both donors and acceptors are localized in quantum wells). The studies were carried out in the near-IR range at helium temperatures. Luminescence lines due to electron transitions from donor states to the first heavy-hole subband (D–hh1) and from the first electron subband to acceptor states (e1–A) have been identified. At large electric currents, the near-IR lasing due to these transitions was observed in the electroluminescence spectra. It has been found that the integrated lasing intensity related to the D–hh1 transitions in the structure without a spatial separation of donors and acceptors was three times higher than in the structure with the spatial separation. It is these transitions that ensure effective depletion of donor levels, which is important for the donor-assisted terahertz emission at e1–D electron transitions. The results of the work can be used in the development of electrically pumped terahertz emitters.

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.

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

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.

We report the development of laser diode microarrays with a cavity length of 6 mm, which include emitting regions 5 × 100 μm in size with a fill factor of 25

A series of heterostructure designs of low-voltage InP homothyristors have been investigated using numerical simulation methods. The design with a space charge layer formed in the p-base region of the n‒p‒n transistor part was considered as the base one. The dynamic characteristics and processes that determine the rate of transition to the on state are investigated. It is shown that as the p-base thickness increases from 1 to 2.6 μm, the maximum on-state currents increase from 70 to 90 A, while the minimum turn-on transition time is 11 ns at a maximum blocking voltage of 55 V. It is shown that the operation efficiency in the on state is determined by the residual voltage. Residual voltage decreases with a decrease in the thickness of the p-base.

Current switches based on low-voltage InP heterothyristors with a maximum blocking voltage of 20 V were developed and studied. In current pulse generation mode, the efficient operation of InP heterothyristors with a low-resistance load in the form of a capacitor was demonstrated. It has been shown that the minimum turn-on delay time is about 6 ns at a control current amplitude of 60 mA. The possibility of generating current pulses with a duration of 53–154 ns and amplitudes of 38–130 A was demonstrated when the capacitor values were changed in the range of 56–1000 nF.

The effect of the active region design on the vertical far-field divergence is studied for high-power laser diodes based on asymmetric heterostructures with a 4-μm thick waveguide and active region designs based on single (SQW) and double (DQW) InGaAs quantum wells. It is shown that the number of quantum wells has a significant effect on the divergence determined by the angle with the 95

Current switches based on low-voltage InP heterothyristors with a maximum blocking voltage of 20V were developed and studied. In current pulse generation mode, the efficient operation of InP heterothyristors with a low-resistance load in the form of a capacitor was demonstrated. It has been shown that the minimum turn-on delay time is about 6 ns at a control current amplitude of 60 mA. The possibility of generating current pulses with a duration of 53–154 ns and amplitudes of 38–130 A was demonstrated when the capacitor values were changed in the range of 56–1000nF.

The influence of a thin AlInAs energy barrier on the efficiency of 1550 nm high-power semiconductor lasers efficiency has been experimentally studied. It was shown that the position and number of barriers in an asymmetric laser heterostructure based on a 1.8-1.9 mu m thick waveguide has a significant effect on the output optical power. It is shown that in a barrierless structure, the main reason for radiative efficiency decrease is internal quantum yield drop due to the absence of an energy barrier for the type-II heterojunction at the waveguide-pcladding interface and electron leakage to the p-emitter layer. It is demonstrated that the implementation of single AlInAs energy barrier layer on waveguide-p-cladding heterojunction allows significantly increase laser diode maximum output power. 2 W maximum CW optical power has been achieved from 40 mu m aperture laser diode at heatsink temperature 25 degrees C.

Uncooled bridge photodetectors based on InAs/InAsSbP heterostructures for the mid-IR region of the spectrum are presented. The bridge structure is distinguished by the fact that the contact pad is placed outside the photosensitive mesa and is connected to it only by an air bridge contact. This design makes it possible to reduce the area of the p–n junction and the capacitance of the device, which leads to an increase in speed without loss of detectivity. The InAs/InAsSbP heterostructures were grown by vapor-phase epitaxy on InAs substrates with (111) orientation. The developed photodetectors have maximum spectral sensitivity in the range of 2.8–3.1 μm and differential resistance at zero shift R0 = 1.0–5.6 kΩ. The capacitance of the best devices is C = 3.4–3.6 pF at Urev = 0 V. The speed of the photodetectors was studied with an InGaAsP/InP laser with emission wavelength of 1.55 μm. The response time determined from the leading edge of the photoresponse is 200 ps. The created bridge photodetectors can be used to detect laser pulses in the range of 1.1–3.8 μm.