We report room temperature injection lasing in the yellow-orange spectral range (599-605 nm) in (Al
Ga
)
In
P-GaAs diodes with 4 layers of tensile-strained In
Ga
P quantum dot-like insertions. The ...wafers were grown by metal-organic vapor phase epitaxy side-by-side on (811), (211) and (322) GaAs substrates tilted towards the direction with respect to the (100) surface. Four sheets of GaP-rich quantum barrier insertions were applied to suppress leakage of non-equilibrium electrons from the gain medium. Laser diodes having a threshold current densities of ~7-10 kA/cm
at room temperature were realized for both (211) and (322) surface orientations at cavity lengths of ~1mm. Emission wavelength at room temperature ~600 nm is shorter by ~8 nm than previously reported. As an opposite example, the devices grown on (811) GaAs substrates did not show lasing at room temperature.
An improved technique for thermal resistance measurement 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 construction of a semiconductor laser with a stripe waveguide is proposed, the geometry of which can make it possible to obtain radiation similar to that of a phase-locked laser array. The ...requirements for the parameters of the laser quasi-array and the technological feasibility of the proposed approach are discussed.
•The sources of errors in thermal resistance measurements are discussed.•Spontaneous spectra allow measuring the active region temperature accurately.•Reducing of thermal resistance owning to the ...laser design optimization was measured.•Coupled-waveguides-based laser design reduceinternal loss and thermal resistance.
Thermal resistance of diode lasers with different waveguide designs has been investigated. Coupled large optical cavity (CLOC) design allows reducing internal loss and heterostructure thermal resistance of high-power InGaAs/GaAs/AlGaAs laser diodes due to the thinned p-claddings and the active region located close to the wafer p-side. Using a simple model we have calculated the thermal resistance of the heterostructure of broad-area lasers and compared the CLOC design with the reference one as well as with some of the best designs of present-day high-power lasers. The improved measurement technique has enabled us to measure reducing of thermal resistance associated with optimization of the laser wafer design. The experimental data are in good agreement with the calculations. A combination of the broadened waveguide, low internal loss and thermal resistance has resulted in good high-power performance of CLOC lasers.
In a laser with asymmetric barrier layers (ABLs) two thin barrier layers adjacent to the active region on both sides are intended to prevent bipolar population of the waveguide layers, hence, to ...suppress parasitic recombination in them. A theoretical model of a laser with ABLs, based on rate equations which acknowledge undesirable carrier leakage inevitable in lasers of this type implemented in practice, is proposed. Solutions to equations are obtained for the steady-state case. By the example of an InGaAs/GaAs quantum-well laser (lasing wavelength λ = 980 nm), the effect of leakages through ABLs on the device characteristics is studied. The parasitic-flux suppression ratios
C
of ABLs which are required to prevent the adverse effect of waveguide recombination are estimated. In the case at hand, the effect of ABLs becomes appreciable at suppression ratios of
C
≥ 10
2
. To suppress 90% of the parasitic current,
C
should be 2.3 × 10
4
. The effect of ABLs on useful carrier fluxes arriving at the active region is also studied.
We report on low threshold current density (<400 A cm−2) injection lasing in (AlxGa1-x)0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on ...high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange-red laser diode structure low threshold current density (190 A cm−2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ∼2 kA cm−2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.
We present an approach for the treatment of coupled-ridge lasers using focused ion beam (FIB) etching. We show experimentally that the FIB etching allows post-processing lateral mode tuning without ...deterioration of the main laser parameters.
Edge-emitting lasers with active regions based on novel InGaAs/GaAs quantum heterostructures of transitional dimensionality, i.e., quantum well-dots, which are intermediate in properties between ...quantum wells and quantum dots, are studied. It is shown that the rate of the lasing-wavelength blue shift decreases with increasing number of quantum well-dot layers in the active region and with increasing optical confinement factor as the cavity length decreases. In a laser with 10 quantum well-dot layers, the lasing-wavelength position remains within the limits of the fundamental optical transition down to the smallest cavity lengths (100 μm). In devices with a single quantum well-dot layer and/or with a low optical confinement factor, lasing directly switches from the ground state to waveguide states omitting excited states below ≤200 μm. Such an effect has not been observed in quantum-well- and quantum-dot lasers and can be attributed to the abnormally low density of excited states in quantum well-dots.
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.
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.
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