2019, Brée, Carsten, Raab, Volker, Montiel-Ponsoda, Joan, Garre-Werner, Guillermo, Staliunas, Kestutis, Bandelow, Uwe, Radziunas, Mindaugas

A brightness- and power-scalable polarization beam combining scheme for high-power, broadarea semiconductor laser diodes is investigated numerically and experimentally. To achieve the beam combining, we employ Lyot-filtered optical reinjection from an external cavity, which forces lasing of the individual diodes on interleaved frequency combs with overlapping envelopes and enables a high optical coupling efficiency. Unlike conventional spectral beam combining schemes with diffraction gratings, the optical coupling efficiency is insensitive to thermal drifts of laser wavelengths. This scheme can be used for efficient coupling of a large number of laser diodes and paves the way towards using broad-area laser diode arrays for cost-efficient material processing, which requires high-brilliance emission and optical powers in the kW-regime.

2018, Brée, Carsten, Gailevicius, Darius, Purlys, Vytautas, Werner, Guillermo Garre, Staliunas, Kestutis, Rathsfeld, Andreas, Schmidt, Gunther, Radziunas, Mindaugas

We derive and analyze an efficient model for reinjection of spatially filtered optical feedback from an external resonator to a broad area, edge emitting semiconductor laser diode. Spatial filtering is achieved by a chirped photonic crystal, with variable periodicity along the optical axis and negligible resonant backscattering. The optimal chirp is obtained from a genetic algorithm, which yields solutions that are robust against perturbations. Extensive numerical simulations of the composite system with our optoelectronic solver indicate that spatially filtered reinjection enhances lower-order transversal optical modes in the laser diode and, consequently, improves the spatial beam quality.

2014, Radziunas, Mindaugas, Herrero, Ramon, Botey, Muriel, Staliunas, Kestutis

We simulate and analyze how beam quality improves while being amplified in edge emitting broad area semiconductor amplifiers with a periodic structuring of the electrical contacts, in both longitudinal and lateral directions. A spatio-temporal traveling wave model is used for simulations of the dynamics and nonlinear interactions of the optical fields, induced polarizations and carrier density. In the case of small beam amplification, the optical field can be expanded into few Bloch modes, so that the system is described by a set of ODEs for the evolution of the mode amplitudes. The analysis of such model provides a deep understanding of the impact of the different parameters on amplification and on spatial (angular) filtering of the beam. It is shown that under realistic parameters the twodimensional modulation of the current can lead not only to a significant reduction of the emission divergence, but also to an additional amplification of the emitted field.

2013, Radziunas, Mindaugas, Botey, Muriel, Herrero, Ramon, Staliunas, Kestutis

We investigate beam shaping in broad area semiconductor amplifiers induced by a periodic modulation of the pump on a scale of several microns. The study is performed by solving numerically a (2+1)-dimensional model for the semiconductor amplifier. We show that, under realistic conditions, the anisotropic gain induced by the pump periodicity can show narrow angular profile of enhanced gain of less than one degree, providing an intrinsic filtering mechanism and eventually improving the spatial beam quality.

2011, Radziunas, Mindaugas, Staliunas, Kestutis

The spatial ``rocking'' is a dynamical effect converting a phase-invariant oscillatory system into a phase-bistable one, where the average phase of the system locks to one of two values differing by $pi$. We demonstrate theoretically the spatial rocking in experimentally accessible and practically relevant systems -- the broad area semiconductor lasers. By numerical integration of the laser model equations we show the phase bistability of the optical fields and explore the bistability area in parameter space. We also predict the spatial patterns, such as phase domain walls and phase solitons, which are characteristic for the phase-bistable spatially extended pattern forming systems.

2012, Radziunas, Mindaugas, Staliunas, Kestutis

The spatial ``rocking'' is a dynamical effect converting a phase-invariant oscillatory system into a phase-bistable one, where the average phase of the system locks to one of two values differing by pi. We demonstrate theoretically the spatial rocking in experimentally accessible and practically relevant systems -- the broad area semiconductor lasers. By numerical integration of the laser model equations we show the phase bistability of the optical fields and explore the bistability area in parameter space. We also predict the spatial patterns, such as phase domain walls and phase solitons, which are characteristic for the phase-bistable spatially extended pattern forming systems.

2015, Radziunas, Mindaugas, Herrero, Ramon, Botey, Muriel, Staliunas, Kestutis

We perform a detailed theoretical analysis of the far field narrowing in broad-area edgeemitting semiconductor amplifiers that are electrically injected through the contacts periodically modulated in both, longitudinal and transverse, directions. The beam propagation properties within the semiconductor amplifier are explored by a (1+2)-dimensional traveling wave model and its coupled mode approximation. Assuming a weak field regime, we analyze the impact of different parameters and modulation geometry on the narrowing of the principal far field component.