1,720,971 research outputs found
Pattern formation in multistacked-quantum-dot-based microcavities: modelization and role of gain asymmetries in the alpha factor - art. no. 64681B
No full textWe develop a model that describes the optical response of a semiconductor quantum dot microcavity pumped above transparency but kept slightly below threshold. The model takes into account the inhomogeneous broadening of the dot emission, the coupling mechanisms between quantum dots and the wetting layer and incorporates gain asymmetry factors in the thermo-emission and capture coefficients. The role of asymmetries with respect to alpha factor and pattern formation is investigated. We then study the conditions for the onset of bistability and modulational instability and characterize the patterns formed
Cavity Solitons in semiconductor microresonators: Modeling aspects and role of thermal carrier-lattice dynamics
No full textWe study Optical Pattern Formation and Cavity Solitons in semiconductor microcavities. We adopt a microscopic model that describes the field, the carrier and the temperature dynamics in the quasi-equilibrium regime, within the free-carrier approximation. A detailed study of the instabilities affecting the homogeneous stationary state of the output field is performed. In this way we can address the numerical research of pattern and Cavity Solitons
Thermal effects and cavity solitons in passive semiconductor microresonators
No full textWe formulate a model including the thermal dynamics in the time evolution of a passive semiconductor microresonator, containing a bulk medium, driven by a coherent holding beam. Thermal effects are taken into account via a dynamical equation for the lattice temperature, describing heat dissipation toward the environment, heating due to carrier generation, and thermal diffusion. The temperature dynamics is coupled to the carrier and field dynamics via the material susceptibility, a red-shift of the band-gap energy of the semiconductor upon an increase of temperature and a linear shift of the cavity resonance. The presence of thermal effects introduces a Hopf instability which, in certain regions of the parameter space, dominates the dynamics of the system. In this case our numerical simulations show that the output intensity may oscillate for constant holding beam intensity (regenerative oscillations), and if the input intensity grows slowly enough the hysteresis cycle may be inverted (switching point inversion). Oscillatory instabilities can also develop a modulational character, meaning that travelling patterns can be found. These phenomena develop over the slow timescale (microseconds) characterizing thermal effects in these devices. In other parameter regimes, the well-known Turing instability giving rise to stationary modulated patterns prevails, and the system displays the usual scenario of stable patterns and cavity solitons. Thermal effects seem not to play any relevant role in these regimes
Model for optical pattern and cavity soliton formation in a microresonator with self-assembled semiconductor quantum dots
No full textWe have developed a model that describes the optical response of a semiconductor quantum dot medium in a cavity in order to investigate pattern and cavity solitons formation. This model, beyond the inclusion of the inhomogeneous broadening of the quantum dot linewidth [1] (due the fluctuations of the quantum dot sizes that arise in self-organized growth), takes into account more complex phenomena such as the thermal escape and capture as well as Auger scattering mechanisms coupling the quantum dot itself with the wetting layer, and carrier diffusion in the unconfined directions of the wetting layer. We have studied the conditions for the onset of bistability and modulational instability and characterize the patterns formed at the bifurcated solutions. New features brought by these terms and indications on the most favourable regimes for cavity solitons formation are discussed
Three-dimensional pattern formation in semiconductor microcavities - art. no. 67251S
No full textWe study pattern formation in a paraxial model for an unidirectional ring resonator filled with a semiconductor sample and driven by a coherent injected field beyond the mean field limit (MFL). We perform numerical simulations to describe the three-dimensional dynamics of the coherent field profile. For fast media spontaneous self-confinement leads to the formation of 3D dissipative addressable spatial solitons, we show that for carrier dynamics compatible with GaAs/GaAlAs MQW devices longitudinal self-confinement is hindered by the slow carrier interband dynamic
Modeling pattern formation and cavity solitons in quantum dot optical microresonators in absorbing and amplifying regimes
No full textWe present a complete overview of our investigation past and present of the modelization and study of the spatiotemporal dynamics of a coherent field emitted by a semiconductor microcavity based on self-assembled quantum dots. The modelistic approach is discussed in relation to prospective growth and experimental research, and the model is then applied to resonators for which the medium is either passive (coherent photogeneration of carriers) or active (carrier pumping by current bias). The optical response of the system is investigated, especially in what concerns the linewidth enhancement factor, which turns out to be critical for the onset of self-organized patterns. The regimes in which one can expect bistable response, modulational instabilities, pattern formation, and cavity soliton formation are investigated. The pattern scenario is described, and experimentally achievable conditions are predicted for the occurrence of stable cavity solitons. (c) 2007 American Institute of Physics
3D self-organized patterns in the field profile of a semiconductor resonator
No full textWe cast a suitable model to describe the 3D dynamics of the coherent field in a monolithic multi-quantum-well (MQW) microresonator within and beyond the mean field limit (MFL) and provide a stability analysis and discriminating criteria to predict 3D pattern formation. While for fast media spontaneous self-confinement leads to the formation of 3D dissipative addressable spatial solitons, we show that for carrier dynamics compatible with GaAs/GaAlAs MQW devices longitudinal self-confinement is hindered by carrier 'sleuth'. We discuss turnaround strategies thereof
Optical patterns and cavity solitons in quantum-dot microresonators
No full textWe study optical transverse instabilities in quantum-dot (QD) microresonators. We develop a model for the QD susceptibility taking into account the inhomogeneous broadening of the dot emission. A linear stability analysis and numerical integration of the resulting equations are performed. Special attention is paid to the formation of such structures as optical patterns and cavity solitons, which could play an important role in the field of optical information processing. Implications for actual QD materials are discussed in view of applications
Cavity solitons in passive bulk semiconductor microcavities. I. Microscopic model and modulational instabilities
No full textWe consider a broad-area vertical microresonator with an active layer constituted by bulk GaAs driven by an external coherent homogeneous electromagnetic field, and we adopt a microscopic model that describes the field and carrier dynamics in the quasi-equilibrium regime. The theory is developed within the free-carrier approximation, with some relevant effects, such as the Urbach tail and the bandgap renormalization, which are taken into account in a phenomenological way. We include in the model the description of paraxial diffraction and carrier diffusion. A detailed study of the instabilities, both modulational and plane wave, affecting the homogeneous stationary state of the output field is performed. In this way we address the numerical research of cavity solitons, which appear as self-organized light peaks embedded in a homogeneous background, as discussed in a companion paper [J. Opt. Sec. Am. B 16, 2095 (1999)]. Optimal conditions for cavity solitons' existence are found in extended regions of the parameter space. (C) 1999 Optical Society of America [S0740-3224(99)01011-5]
The physics of cavity solitons in semiconductor microcavities
No full textWe start by reviewing the basic physical properties of cavity solitons, embedding this phenomenon in the general framework of optical instabilities and optical pattern formation. Next, we focus on the case of semiconductor microcavities and consider a first principle model. Its homogeneous stationary solutions and their stability are evaluated analytically. With the help of numerical simulations, we discuss two case studies, one in the passive and one in the active configuration
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