We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of $\sim 22°$ FWHM (full width at half-maximum) in CW (continuous-wave) operation.

Gaseous phase epitaxy from metal organic compounds is used to obtain a low-temperature injection laser with an active region based on In0.5Ga0.5As/GaAs quantum dots. Optimizing the growth conditions a

We study material gain of a novel type of quantum heterostructures of mixed (0D/2D) dimensionality referred to as quantum well-dots (QWDs). To evaluate the material gain in a broad range of injection currents (30–1200 A cm ⁻² per-layer) we studied edge-emitting lasers with various numbers of InGaAs/GaAs QWD layers in the active region and different waveguide designs. The dependence of the material gain on the current is well fitted by an empirical exponential equation similar to the one used for quantum dots (QDs) in the whole range of injection current densities. The estimated QWD transparency current-density-per-layer of 31 A cm ⁻² ranks between the values reported for quantum wells and QDs. The maximal QWD material gain as high as 1.1⋅10 ⁴ cm ⁻¹ has been measured. The results obtained confirm specific gain properties of InGaAs QWDs making them promising active media for lasers, superluminescence diodes and optical amplifiers.

The relaxation mechanisms of an array of 10 vertically coupled layers of InGaAs/AlGaAs quantum dots were studied by time-resolved photoluminescence. Both resonant and non-resonant excitation were employed and the photoluminescence (PL) intensity in the non-resonant case is a factor of 200 larger than the intensity with resonant excitation. The results obtained in the non-resonant pumping experiment were analysed with a rate equation model. It was found that the PL decay time increases rapidly with the wavelength of detection. Large carrier capture cross-sections [(2.5±0.9)×10^-5 cm³/s] were deduced, resulting in a capture time of 1 ps for a carrier concentration of 4×10¹⁶ cm^-3. A very fast PL risetime was observed with resonant pumping, ruling out a phonon bottleneck effect in these samples. The decay times at a given wavelength are always shorter for resonant than for non-resonant excitation and their difference increases rapidly with wavelength. This is interpreted in terms of a state filling effect for the non-resonant case.

The key principles of transverse mode engineering in edge-emitting lasers with broadened waveguides based on coupled large optical cavity (CLOC) structures are presented. The CLOC laser design is shown to be an effective approach for reducing the optical loss, broadening the waveguide, and lowering the beam divergence. Having simulated the sensitivity of the CLOC design to variations in layer thicknesses and compositions we have shown its high robustness. Advanced versions of the CLOC laser structures having two extra passive waveguides have been treated and shown to effectively eliminate several transverse modes. We have considered an application of the CLOC concept for waveguides with shifted active regions aimed at reducing laser thermal and electric resistances.

Semiconductor lasers have developed rapidly with the steady growth of the global laser market. The use of semiconductor laser diodes is currently considered to be the most advanced option for achieving the optimal combination of efficiency, energy consumption, and cost parameters of high-power solid-state and fiber lasers. In this work, an approach for optical mode engineering in planar waveguides is investigated. The approach referred to as Coupled Large Optical Cavity (CLOC) is based on the resonant optical coupling between waveguides and allows the selection of high-order modes. The state-of-art of the CLOC operation is reviewed and discussed. We apply the CLOC concept in our waveguide design strategy. The results in both numerical simulation and experiment show that the CLOC approach can be considered a simple and cost-efficient solution for improving diode laser performance.