1,721,040 research outputs found
Pulsing and excitable solitons in a semiconductor laser with saturable absorber
No full textCavity solitons (CS) are controllable localized light peaks on a low-intensity, homogeneous (or quasi-homogeneous) background and offer a variety of applications from optical memories to all-optical delay lines. A semiconductor laser (VCSEL) with an intracavity saturable absorber realizes a cavity soliton laser, where the CS sit over a zero-intensity background, and may behave as independent microlasers. © 2011 IEEE
Control of spatiotemporal rogue waves by harmonic pump modulation in a semiconductor laser with a saturable absorber
Full text linkThrough numerical simulations, statistical and dynamical properties of extreme events in a broad-area semiconductor laser with intracavity saturable absorber are investigated. By inclusion of a diffusion coefficient for the field, formation of rogue waves in a state of extended turbulence is studied and shown to be affected by harmonic perturbations. In particular, we propose a control technique based on periodic modulation of the pump parameter which can either drive the state of the system closer to or away from the chaotic attractors respectively enhancing or suppressing the generation of rogue waves. By statistical and dynamical analysis of the events in terms of intensity and optical gain, we show that when the system is under resonant modulation with frequency close to that of the dominant oscillations in the turbulent state (which is equal to the relaxation oscillation frequency typical of semiconductor lasers), more rogue waves are triggered with larger intensities and shorter lifetimes. On the other hand, off-resonant modulations restrain the formation of rogue waves where they appear in lower intensities and longer lifetimes. An example of special cases where the proposed scheme can completely forbid or allow the emission of rogue waves is also presented
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
Thermal instabilites in semiconductor amplifiers
No full textWe introduce here a model which includes the thermal dynamics in the time evolution of a semiconductor Multiple quantum well microresonator, driven by a coherent holding beam. The active layer is electrically pumped, in order to obtain population inversion, but it is maintained below the lasing threshold. We show that the inclusion of thermal effects introduces a Hopf instability which may dominate the dynamical behaviour of the system in some operational regimes. In those cases our numerical simulations show that both spatial patterns and cavity solitons perform a drift motion in the transverse direction. This motion develops over the slow time scale which characterizes thermal effects
Controlling cavity solitons by means of photorefractive soliton electro-activation
No full textWe consider a hybrid system consisting of a centrosymmetric photorefractive crystal in contact with a verticalcavity surface-emitting laser. We numerically investigate the generation and control of cavity solitons (CSs) by propagating a plane wave through electro-activated solitonic waveguides in the crystal. In such a compound scheme, which couples a propagative/conservative field dynamics to a bistable/dissipative one, we show that by changing the electro-activation voltage of the crystal, the CSs can be turned on and shifted with controlled velocity across the device section, on the scale of tens of nanoseconds. The configuration can be exploited for applications to optical information encoding and processin
Controlling cavity solitons by means of photorefractive soliton electro-activation
No full textWe consider a hybrid system consisting of a centrosymmetric photorefractive crystal in contact with a verticalcavity surface-emitting laser. We numerically investigate the generation and control of cavity solitons (CSs) by propagating a plane wave through electro-activated solitonic waveguides in the crystal. In such a compound scheme, which couples a propagative/conservative field dynamics to a bistable/dissipative one, we show that by changing the electro-activation voltage of the crystal, the CSs can be turned on and shifted with controlled velocity across the device section, on the scale of tens of nanoseconds. The configuration can be exploited for applications to optical information encoding and processing. (C) 2012 Optical Society of Americ
Self-propelled soliton collisions in a semiconductor Cavity Soliton Laser
No full textSpontaneous soliton motion has been demonstrated in different systems supporting cavity solitons. Here we consider the case of a semiconductor laser with an intracavity saturable absorber, and study the interactions between self-propelled solitons when two of them collide or when they hit a localised defect in the material gain. According to the soliton velocity and impact parameter, destructive or repulsive collisions may take place between travelling solitons. On the other hand, a very rich variety of dynamical behaviors can be observed when a travelling soliton hits a material defect of comparable size. We observe soliton destruction, repulsive or attractive interaction and two trapped cases. The behavior is mainly determined by the gain contrast between the defect and the background
Soliton dynamics in a semicondutor cavity soliton laser with broken translational symmetry
No full textThermal and electronic nonlinearities in semiconductor cavities
No full textIn this paper we study the dynamics of a semiconductor microcavity containing a bulk medium, driven by an external coherent field. Thermal effects are taken into account through a temperature dependence of the band-gap energy of the semiconductor, that appears in the nonlinear susceptibility. The susceptibility contains the information about nonlinear absorption and refractive index changes and it is developed in the framework of a free-carrier theory, with a few many-body correction (Urbach tail, band-gap renormalisation) introduced phenomenologically. As a first approximation we consider Plane Wave case, eliminating diffusing or diffractive effects. We are able to obtain global dynamical effects such as thermally induced Regenerative Oscillations or switching point inversion. The results we present are preliminary to a further study of the combination of spatial and thermal effects, still in progress
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