The possibility of fabrication of 4.6 μm spectral range quantum-cascade laser heterostructures by molecular-beam epitaxy technique with non-selective overgrowth by the metalorganic vapour-phase epitaxy is shown. The active region of the laser was formed on the basis of a heteropair of In0.67Ga0.33As/In0.36Al0.64As solid alloys. The waveguide claddings are formed by indium phosphide. The results of surface defects inspection and X-ray diffraction analysis of quantum-cascade laser heterostructures allow to conclude that the structural quality of the heterostructures is high and the estimated value of the root mean square surface roughness does not exceed 0.7 nm. Lasers with four cleaved facets exhibit lasing at room temperature with a relatively low threshold current density of the order of 1 kA/cm2. Keywords: superlattices, quantum-cascade laser, epitaxy, indium phosphide.

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.

We report a study of electrical and optical characteristics of a new emitter design based on a vertical stack of a laser diode minibar (LDMB) and a 2D multielement thyristor array (2D META) as a high-current switch designed for the generation of short (tens of nanoseconds) high-power laser pulses. It is found that a reduction of the anode contact size of single 2D META elements down to 200 μm provides conditions for the uniform inclusion of all the elements. It is shown that in the regime of “long” pulses (14.6 ns), the peak laser power reaches 85 W at a wavelength of 1060 nm, which corresponds to a peak current of 119 A, generated in the vertical stack circuit (19.8 A per single 2D META element); in this case, the maximum pulse repetition rate for an operating voltage of 15 V reaches 700 kHz. In the regime of “short” pulses (6.4 ns) at a repetition rate of 1 MHz, the peak optical power reaches 47 W at the same wavelength, which corresponds to a generated peak current of 60 A (10 A per single 2D META element). It is shown that in both operation modes, the characteristics of the 2D META as a high-current switch do not change with increasing repetition rate.

The In 0.37 Al 0.63 As/In 0.65 Ga 0.35 As/In 0.53 Ga 0.47 As quantum-cascade lasers for 7–8 μm spectral range have been fabricated and studied. The use of a multicomponent active region with a diagonal optical transition and single-phonon resonance depopulation scheme, along with strain-balanced heteropair, made it possible to reduce the threshold current densities and voltage.

We study room-temperature performance of high-power mid-infrared quantum cascade lasers fabricated from the heterostructures grown by a combination of MBE and MOCVD epitaxial methods.

Approaches to improve the L- I characteristics of laser diodes emitting at 940–980 nm based on InGaAs/AlGaAs/GaAs separate confinement double heterostructures with an asymmetric broadened waveguide are studied. The influence of the waveguide composition on the lasers output characteristics is analyzed. It is shown that a decrease in the energy depth of the QW leads to a decrease in series and thermal resistances and cut-off voltage that allows to improve output characteristics.

The purpose of this work is to improve the current – voltage ( I – V ) performance of semiconductor lasers based on broadened asymmetric waveguide InGaAs/AlGaAs/GaAs separate-confinement double heterostructures. We analyse the effect of AlGaAs waveguide layer composition on the output characteristics of the lasers and demonstrate that the decrease in the series resistance of the lasers and the threshold voltage of their I – V characteristic as a result of a decrease in the percentage of AlAs in the waveguide layers shifts the drop in the differential quantum efficiency of the lasers to higher pump currents, despite the decrease in the energy depth of the quantum wells in the active region.

We study 8 µm -emitting quantum-cascade lasers with different compositions of upper cladding. The maximum room-temperature peak power exceeds 14W, which is the highest reported value at this wavelength to the best of our knowledge.

The possibility of fabrication of 4.6 µm spectral range quantum-cascade laser heterostructures by molecular-beam epitaxy technique with non-selective overgrowth by the metalorganic vapour-phase epitaxy is shown. The active region of the laser was formed on the basis of a heteropair of In0.67Ga0.33As/In0.36Al0.64As solid alloys. The waveguide claddings are formed by indium phosphide. The results of surface defects inspection and X-ray diffraction analysis of quantum-cascade laser heterostructures allow to conclude that the structural quality of the heterostructures is high and the estimated value of the root mean square surface roughness does not exceed 0.7 nm. Lasers with four cleaved facets exhibit lasing at room temperature with a relatively low threshold current density of the order of 1 kA /cm2.

High-power semiconductor lasers based on AlGaInAs/InP heterostructures and emitting in the spectral range 1.9−2.0 μm are developed. Strain compensation in the active region makes it possible to use InGaAs quantum wells with a compressive strain of about 2.0 %−2.5 %. The operation of a laser with an ultra-narrow waveguide at wavelengths increasing from 1.4−1.6 to 2.0 μm is studied. At room temperature, the semiconductor lasers with a stripe contact width of 100 μm demonstrates a cw output optical power of 1.0 W with a wavelength of 1.91 μm at a pump current of 6.5 A and with a wavelength of 1.98 μm at a pump current of 7.2 A.

Semiconductor lasers based on AlGaInAs/InP heterostructures with ultra-narrow and asymmetric waveguides are comparatively studied. It is shown that the use of these waveguides with a simultaneous increase in the quantum well depth makes it possible to increase output powers. Such lasers based on both strongly asymmetric and ultra-narrow waveguides with a stripe contact width of 100 μm demonstrate an output power of 5 W (at pump currents of 11.5 and 14 A, respectively) in a continuous-wave regime at room temperature and a wavelength of 1450 – 1500 nm.

Today, widening the aperture is considered as one of approaches in development of high-power pulsed semiconductor lasers [1] , [2] . Aperture widening increases the linearity of the light-current characteristic in the region of high currents by reducing the current density, which is important for high-power pulsed laser sources. In addition, in contrast to typical designs of laser diode arrays with a width of the aperture of 100-200 µm, the aperture widening increases the fill factor. Here we study the approach based on the use of epitaxially integrated laser heterostructures and an ultra-wide apertures for high-power pulsed laser sources.

The article presents a new design of an AlGaAs/GaAs low-voltage thyristor for efficient high-current pulse generation at high repetition rates. It is demonstrated that optimizing the low-voltage thyristor p-base doping profile by using a thin highly doped layer allows for a significant increase in the operating frequencies. This applies to both a thyristor working without an external load and a vertical stack of a thyristor with a laser diode mini bar (LDMB). It is shown that the use of a 0.1- $\mu \text{m}$ -thick highly doped layer, formed at the side of the p-base close to the n-emitter, leads to a significant increase of the holding current, which in our case exceeds 70 mA. At the same time, we were still able to obtain a low residual voltage of 1.5 V and a high blocking voltage of 32 V. The developed low-voltage thyristors have demonstrated the possibility of generating current pulses of 30-ns duration at a repetition rate of 10/70 kHz with an amplitude of 125/110 A, as well as the efficient pumping of LDMBs and laser pulses with a peak power of 68/57.5 W, respectively.

Semiconductor lasers based on double separate-confinement InGaAs/AlGaAs/GaAs heterostructures with a broadened waveguide are studied. The experimentally obtained samples of lasers with undoped and doped waveguide layers are compared. The differences in their current–voltage characteristics are analysed. It is found that a decrease in the series resistance and the cutoff voltage of the current–voltage characteristic makes it possible to delay the beginning of the output optical power saturation and increase the efficiency of the studied semiconductor lasers to 70 %−72 %.

A triple laser – thyristor, i. e., a semiconductor laser with three emitting sections monolithically integrated with an electronic switch (thyristor) is experimentally studied. For comparison, the output characteristics of single and double laser – thyristors are presented. It is shown that the functional integration of a laser with a thyristor in one heterostructure allows the laser to efficiently operate in a pulsed regime (output power ∼50 W), the use of vertical integration of two laser sections increases the power to ∼90 W, and the integration of three laser sections makes it possible to increase the output optical power to ∼120 W with all other conditions being the same.

The influence of doping of waveguide layers on the output characteristics of lasers based on AlGaAs/GaAs double separate-confinement heterostructures is analysed. The heterostructures with narrow and broadened waveguides are studied. Samples of laser diode bars with undoped and doped waveguide layers are experimentally fabricated and compared. It is shown that the latter type of structures with a broadened waveguide allows one to increase the output power of the laser diode bars by 10 % – 15 %, all other conditions being equal.

Semiconductor lasers based on AlGaInAs/InP heterostructures with an ultra-narrow waveguide and an increased electron barrier layer are developed. It is shown that the use of this waveguide in conjunction with profiled doping ensures a balance between internal optical losses and heat resistance. Additional use of strained wide-bandgap layers as blocking barriers limiting electron leakage from the active region makes it possible to increase the output power at the same pump current. The developed lasers with a stripe contact 100 μm wide demonstrate at room temperature an output optical power of 4.0 – 4.4 W (pump current 14 A) in a continuous-wave regime and 15 – 17 W (100 A) in a pulsed regime (100 ns, 1 kHz) at wavelengths of 1450 – 1500 nm.

Superluminescent diodes (SLDs) of spectral range 730 - 790 nm with strained single quantum-well (SQW) active layer and spatially single mode ridge waveguide were studied experimentally. SLDs with short active channels < 1000 mu m have demonstrated broadband emission spectrum with median wavelength near 765 nm, FWHM of up to 60 nm and free space CW output power in the range 2 - 15 mW at 25 degrees C. SLDs with longer active channels have demonstrated output of up to 150 mW and spectral half-width in the range 40 - 20 nm. TM mode was dominant in output emission.

Superluminescent diodes based on AlGaInAs/InP separate-confinement double heterostructures with strain-compensated quantum wells are investigated. The influence of elastic strains in the active region on the output characteristics of the devices is analysed. It is shown that such a design of a superluminescent diode allows an optical power of more than 5 mW, a radiation spectrum width of more than 60 nm, a degree of output radiation polarisation up to 30 dB to be obtained at the output of a single-mode fibre, and has a great potential for further improvement.