We have studied superluminescent diodes with simplified design and active region based on 5 or 7 layers of InGaAs/GaAs quantum well-dots (QWDs). Emission peaks of the individual QWD layers are shifted with respect to each other by 15-35 nm to provide as wide as possible emission line in a superluminescent mode with central wavelength of about 1 µm without significant spectral dips. For superluminescent diodes with the active region based on 5 and 7 QWD layers, the maximal value of full width at half maximum of emission spectrum was 92 and 103 nm respectively.

A systematic study of a series of InGaAs/GaAs lasers in the 1−1.3 µm optical range based on quantum wells (2D), quantum dots (0D), and quantum well-dots of transitional(0D/2D) dimensionality is presented. In a wide range of pump currents, the dependences of the lasing wavelength on the layer gain constant, a parameter which allows comparing lasers with different types of active region and various waveguide designs, are measured and analyzed. It is shown that the maximum optical gain of the quantum well-dots is significantly higher, and the range of lasing rawavelengths achievable in edge-emitting lasers without external resonators is wider than in lasers based on quantum wells and quantum dots.

An improved technique for thermal resistance mea- surement of edge-emitting diode lasers using spontaneous emission spectra, collected through the opening in the n-contact within the range of operating currents, has been proposed. The advantage of the proposed technique is that systematic errors typical for measurements based on lasing spectra are excluded. The accuracy of the method was verified by measuring the dependence of the thermal resistance on the cavity length for diode lasers with 100 μm strip width. Obtained results are in good agreement with the model, and the minimum measurement error was ±0.1 K/W. The proposed technique can be used in metrological support of fabrication process of semiconductor lasers.

The internal loss at the lasing threshold were studied experimentally and numerically in laser cavities comprising dense arrays of InGaAs/GaAs quantum dots (quantum well-dots) as a function of the number of their planes and the output loss. Numerical values of the parameters were found that determine the free-carrier absorption in the active region and in the waveguiding layer. The optimal design of the laser diode was determined to achieve the highest external differential efficiency.

We studied the influence of the focused ion beam milling of ridge waveguides on lasing parameters of edge-emitting lasers, based on a separate confinement double heterostructure. It is shown that there are three degrees of influence, according to the etching depth: modification of the waveguide properties only, a decrease in efficiency without changing the threshold current, and a simultaneous deterioration in the threshold current and efficiency with significant modification of the optical characteristics of the laser.

We study edge-emitting lasers with the active area based on novel InGaAs/GaAs quantum heterostructures of transitional dimensionality referred to as quantum well-dots, which are intermediate in properties between quantum wells and quantum dots. We show that the rate of the lasing wavelength blue-shift occurring with the reduction in cavity length decreases with an increase in the number of quantum well-dot layers in the active region and the optical confinement factor. In the laser based on 10 quantum well-dot layers, the position of the lasing wavelength remains in the optical region corresponding to the emission from the ground state down to the cavity lengths as short as 100 μm. In the devices based on a single quantum well-dot layer and/or with low optical confinement factor, lasing directly switches from the ground state to the GaAs waveguide states omitting excited state lasing with decrease in cavity length below 200 μm. Such an effect has not been observed in quantum well and quantum dot lasers and is attributed to the abnormally low density of excited states in quantum well-dots.

In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are aimed at prevention of bipolar population of the waveguide layers and, accordingly, at suppression of parasitic recombination in them. In the present work, a theoretical model of the laser with ABLs based on rate equations is proposed, which includes unwanted carrier leakage that inevitably occurs in lasers with ABLs implemented in practice. Solutions of the equations for the steady-state mode are obtained. Using an example of a laser based on an InGaAs/GaAs quantum well (lasing wavelength λ = 980 nm) the effect of the leakage through ABLs on device characteristics is studied. The parasitic fluxes suppression ratios C of ABLs that are required for prevention of unwanted impact of waveguide recombination are estimated. For the case under consideration the effect of using ABLs becomes pronounced at the suppression ratios C ≥ 102. To suppress 90% of the parasitic current, C should be equal to 2.3 · 10^4. In the work, we also study the influence of ABLs on the useful fluxes of carriers entering the active region.

Picosecond optical pulses generation by 1064nm InGaAs/GaAs quantum well distributed feedback lasers was investigated. In the gain-switching regime the duration of laser pulses decreased from 150 to 35 ps with temperature increase from 5 to 50 degrees. The minimal pulses duration 35 ps and spectral width 70 pm was achieved in the optimal temperature range. The laser was placed in sealed butterfly package, which made it possible to obtain wavelength temperature tuning of 3 nm where the pulses duration was less than 45 ps. The output peak power was 0.4 W from single-mode polarization maintaining fiber.

AbstractA post-growth technique aimed at spatial modification of facet reflectance of edge-emitting diode lasers has been proposed. It is based on the deposition of an anti-reflection coating and subsequent precise etching with a focused ion beam. The technique allowed suppressing of high-order lateral modes in 10 μm stripe lasers based on ten layers of InAs/InGaAs quantum dots.

AbstractThe main characteristics of edge-emitting lasers with active regions based on nanoheterostructures of a new type—quantum well-dots (QWDs) operating at various wavelengths—are compared. The QWD structures operating at 980- and 1080-nm wavelengths demonstrated minimum values of threshold current density (160 and 125 A/cm^2), high internal quantum efficiency (74 and 85%), and low internal losses (1.1 and 0.9 cm^–1), respectively.

Lasing in orange spectral range(599−605 nm)in(AlxGa1−x)0.5In0.5P−GaAs laser diodes grown by MOVPE on GaAs substrates(211) and (322) was demonstrated. The active region consisted of 4 layers of InxGa1−xP vertically coupled quantum dots. Carrier leakage from the active area was suppressed by using barriers formed with 4 quantum-sized layers of InGaAlP with high Ga content. The maximum optical power in the pulsed regime was limited by catastrophic optical mirror degradation and reached 800 mW. Lower threshold current density, higher differential efficiency, and lower internal losses were demonstrated by lasers processed from epitaxial structures grown on(322)A substrates in comparison to those grown on(211)A. This fact is due to the higher energy barrier for electrons in the first case.

Microlasers formed by deep etching with an active region based on arrays of InGaAs/GaAs quantum well-dots were studied. The way how the current-voltage characteristic changes with decreasing microlaser diameter indicates the formation of a nonconducting layer about 1.5 μm thick near the side walls, which leads to a decrease in the effective area of current flow

We have proposed a semiconductor laser design with a stripe waveguide, which geometry can make it possible to obtain radiation similar to that of a phase-locked laser array. The requirements for the laser quasi-array parameters and the technological feasibility of the proposed approach are discussed.

AbstractResults are presented of a study of light–current characteristics and far-field patterns of emission of stripe lasers with coupled planar waveguides. This configuration makes it possible to suppress the generation of excited modes and to have a small (about 0.9 μm) depth of the active region from the surface of the laser crystal. A high-temperature stability of the angular emission divergence (34.0° ± 1.5°) in the temperature range 20–80°C is demonstrated. The largest value of the output power is limited to 12.2 W in the continuous-wave mode by the catastrophic mirror damage.

AbstractThe characteristics of lasers of the 1.44–1.46-μm optical range grown on GaAs substrates using a metamorphic buffer are studied. The active region of the laser contains 10 rows of InAs/In_0.4Ga_0.6As/In_0.2Ga_0.8As quantum dots. It is shown that the use of special selective high-temperature annealing along with the application of short-period In_0.2Ga_0.8As/In_0.2Al_0.3Ga_0.5As short-period superlattices makes it possible to substantially decrease the density of threading dislocations in the active region. A threshold current density of 1300 A cm^–2, external differential quantum efficiency of 38%, and maximal pulsed-mode output power of 13 W are attained for a laser with a broad area 3 mm in length.

AbstractThe results of studying edge-emitting quantum-well lasers with a layered design having coupled planar waveguides, capable of suppressing the generation of excited transverse modes, are presented. In this case, a low internal loss (0.4 cm^–1) is provided, combined with a small depth (~0.9 μm) of the active region, which results in a low thermal resistance of 6.0 (K/W) mm without a submount.

AbstractWe have investigated two-sectional semiconductor lasers with an active region comprising five layers of InGaAs quantum dots, emitting in the spectral range near 1.06 μm. Regimes of passive mode-locking, passive Q-switching, and mode-locking with pulse modulated amplitude are realized. The transition conditions between generation regimes are investigated. The frequency tuning range with current increase in the Q-switched regime exceeds more than 4 times. The duration of the mode-locked pulses was 2 ps at the pulse repetition rate of 44.3 GHz.