[en] The effect of modulation p-doping on multi-state lasing in InAs/InGaAs quantum dot (QD) lasers is studied for different levels of acceptor concentration. It is shown that in case of the short laser cavities, p-doping results in higher output power of the ground-state optical transitions of InAs/InGaAs QDs whereas in longer samples p-doping may result in the decrease of this power component. On the basis of this observation, the optimal design of laser active region and optimal doping level are discussed in details. (paper)

[en] The process of obtaining a modified structure for quantum cascade lasers is studied; this process includes growth using molecular-beam epitaxy, plasma etching, photolithography with the use of liquid etching, and the formation of special contacts for decreasing losses in the waveguide. The use of a special type of structure makes it possible, even without postgrowth overgrowth with a high-resistivity material, to attain parameters satisfying requirements to heterostructures in high-quality quantum cascade lasers at maximal simplification of the entire preparation process.

[en] Results are presented on a comparative study of InGaAs/GaAs/AlGaAs coupled large optical cavity (CLOC) laser heterostructures emitting at either 1.03 or 0.98 μm. The smaller energy of carrier localization in the active region of the latter structure leads to stronger carrier leakage out of the quantum well that in its turn results in a higher internal optical loss, higher threshold current density and more pronounced temperature sensitivity. In continuous wave regime, the maximal output power of 8 W in the 0.98-μm lasers is found to be limited by the thermal rollover, whereas in the longer wavelength laser it is 10.8 W being limited by the catastrophic optical mirror damage. (paper)

[en] Quantum well InGaAs/GaAs lasers based on narrow asymmetric waveguide were created and investigated in pulse and CW modes. Broad-area 50μm stripe lasers showed internal quantum efficiency as high as 95%, threshold current density as low as 160 A/cm². Wall-plug efficiency in CW mode reached the value of 75%. The obtained parameters make the concept of narrow asymmetric waveguide promising for high-power laser diodes

[en] We report results of characterization of injection microdisk lasers based on active layers employing 2, 5 and 10 layers of InGaAs quantum well-dot structures. The microlasers operate in continuous wave regime at room temperature without external cooling. The minimal microdisk diameter 10 µm is obtained for 5 layers of InGaAs quantum well-dot structures. Lasing wavelength is around 1.1…1.15 µm, minimal threshold current is 1.6 mA (threshold current density 900 A/cm²). (paper)

[en] An analytical expression is derived for the linewidth enhancement factor of a quantum-dot laser, which makes it possible to describe its dependence on optical loss and photon density in an explicit form. The model accounts for refractive index variations at the ground-state optical transition due to gain/absorption variations upon the first excited-state transition in quantum dots. It is shown that a decrease in optical loss, an increase in saturated gain, and an increase in the energy separation between the excited-state and ground-state transitions results in a decrease in the α factor both at and above the lasing threshold.

[en] We present an experimental study on the edge-emitting lasers based on coupled ridges. The main idea of these structures is to ensure fundamental mode lasing in broadened multi-mode ridges by means of using a high-order mode filtering based on the resonant optical tunneling into a nearby passive stripe. For our experiments, we used a conventional InAs/InGaAs quantum dot (QD) laser wafer (λ∼1.28μm) and placed a 3 μm passive dielectric-covered ridge at the distance of 4 μm from 10 μm main active ridge. The devices demonstrated stable far-field patterns with suppressed first-order mode lasing and without any deterioration of the main laser parameters. However, side lobes in the far-field patterns indicated second-order mode traces attributed to the current spread from the main stripe, which increase the effective stripe width. We assume that optimization of the laser hafer and etching technique may lead to a pure lateral single-mode lasing in the coupled ridge devices. (paper)

[en] Having investigated narrow-ridge lasers based on a single layer of InGaAs quantum well-dots emitting at the wavelength of 1.06 μm we have shown anomalous transverse multimode lasing not observed in the broad-area lasers. The effect is shown to be caused by the wavelength shift triggered by the ground state gain saturation. (paper)

[en] We present a study on minimization of thermal resistance of edge-emitting diode lasers by placing the active region closer to the laser surface. We demonstrate that using coupled large optical cavity (CLOC) approach one can reduce the thickness of the p-cladding down to 0.5 μm due to the strong mode localization in a broad active waveguide (1.35 μm) coupled to a passive optical cavity. Also, the advanced laser design allowed us to put the active region closer to the cladding in comparison with conventional broad waveguide lasers. As a result, a record-low thermal resistance of 2 K/W for 3 mm device directly mounted on a copper heatsink in combination with a low optical internal loss of 0.4 cm⁻¹ where demonstrated. (paper)

[en] A 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.