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Author: Knigge, Andrea × Author: Radziunas, Mindaugas × End date: 2019 × Start date: 2010 × Publisher: Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik ×

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Now showing 1 - 4 of 4
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    Time-dependent simulation of thermal lensing in high-power broad-area semiconductor lasers
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Zeghuzi, Anissa; Wünsche, Hans-Jürgen; Wenzel, Hans; Radziunas, Mindaugas; Fuhrmann, Jürgen; Klehr, Andreas; Bandelow, Uwe; Knigge, Andrea
    We propose a physically realistic and yet numerically applicable thermal model to account for short and long term self-heating within broad-area lasers. Although the temperature increase is small under pulsed operation, a waveguide that is formed within a few-ns-long pulse can result in a transition from a gain-guided to an index-guided structure, leading to near and far field narrowing. Under continuous wave operation the longitudinally varying temperature profile is obtained self-consistently. The resulting unfavorable narrowing of the near field can be successfully counteracted by etching trenches.
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    Simulation and design of a compact GaAs based tunable dual-wavelength diode laser system
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Koester, Jan-Philipp; Radziunas, Mindaugas; Zeghuzi, Anissa; Wenzel, Hans; Knigge, Andrea
    We present our design of a compact, integrated and tunable dual-wavelength diode laser system emitting around 785 nm, which is of interest for several applications like Raman spectroscopy and the generation of THz radiation. To achieve a more compact device compared to previous GaAs based designs two etch depths are realized, leading to shallowly etched ridge waveguides in regions were optical gain is applied and deeply etched waveguides used to enable compact integrated waveguide components. The device parameters are optimized using a numerically efficient simulation tool for passive waveguides. Subsequently, the entire laser system is further analyzed applying a sophisticated traveling-wave equation based model for active devices giving access to internal intensity and carrier density distributions. It is shown that active laser simulations are crucial to deduce critical and performance limiting design aspects not accessible via an all-passive simulation.
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    Traveling wave analysis of non-thermal far-field blooming in high-power broad-area lasers
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Zeghuzi, Anissa; Radziunas, Mindaugas; Wünsche, Hans-Jürgen; Koester, Jan-Philipp; Wenzel, Hans; Bandelow, Uwe; Knigge, Andrea
    With rising current the lateral far-field angle of high-power broad-area lasers widens (far-field blooming) which can be partly attributed to non-thermal effects due to carrier induced refractive index and gain changes that become the dominant mechanism under pulsed operation. To analyze the non-thermal contribution to far-field blooming we use a traveling wave based model that properly describes the injection of the current into and the diffusion of the carriers within the active region. Although no pre-assumptions regarding the modal composition of the field is made and filamentation is automatically accounted for, the highly dynamic time-dependent optical field distribution can be very well represented by only few modes of the corresponding stationary waveguide equation obtained by a temporal average of the carrier density and field intensity. The reduction of current spreading and spatial holeburning by selecting proper design parameters can substantially improve the beam quality of the laser.
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    Modeling of current spreading in high-power broad-area lasers and its impact on the lateral far field divergence
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2018) Zeghuzi, Anissa; Radziunas, Mindaugas; Wenzel, Hans; Wünsche, Hans-Jürgen; Bandelow, Uwe; Knigge, Andrea
    The effect of current spreading on the lateral farfield divergence of highpower broadarea lasers is investigated with a timedependent model using different descriptions for the injection of carriers into the active region. Most simulation tools simply assume a spatially constant injection current density below the contact stripe and a vanishing current density beside. Within the driftdiffusion approach, however, the injected current density is obtained from the gradient of the quasiFermi potential of the holes, which solves a Laplace equation in the pdoped region if recombination is neglected. We compare an approximate solution of the Laplace equation with the exact solution and show that for the exact solution the highest farfield divergence is obtained. We conclude that an advanced modeling of the profiles of the injection current densities is necessary for a correct description of farfield blooming in broadarea lasers.