Alexander Pimenov

Hybrid Mode Locking in Semiconductor Lasers: Simulations, Analysis, and Experiments

Hybrid mode locking in a two-section edge-emitting semiconductor laser is studied numerically and analytically using a set of three delay differential equations. In these equations, the external RF signal applied to the saturable-absorber section is modeled by the modulation of the carrier relaxation rate in this section. The estimation of the locking range where the pulse repetition frequency is synchronized with the frequency of the external modulation is performed numerically and the effect of the modulation shape and amplitude on this range is investigated. Asymptotic analysis of the dependence of the locking range width on the laser parameters is carried out in the limit of small-signal modulation. Our numerical simulations indicate that hybrid mode locking can be also achieved in the cases when the frequency of the external modulation is approximately twice and half of the pulse repetition frequency of the free-running passively mode-locked laser fP . Finally, we provide an experimental demonstration of hybrid mode locking in a 20-GHz quantum-dot laser with the modulation frequency of the reverse bias applied to the absorber section close to fP/2.

Numerical Study of Dynamical Regimes in a Monolithic Passively Mode-Locked Semiconductor Laser

Bifurcation mechanisms of the development and break up of different operation regimes in a passively mode-locked monolithic semiconductor laser are studied by solving numerically partial differential equations for amplitudes of two counterpropagating waves and carrier densities in gain and absorber sections. It is shown that mode-locking regimes with different repetition rates can be multistable for a wide range of laser parameters and that the harmonic mode-locking regime with two counterpropagating pulses in the cavity can exhibit a period-doubling bifurcation leading to different amplitudes and separations of the pulses. The effect of linewidth enhancement factors in gain and absorber sections on the laser dynamics is discussed.

Timing jitter of passively-mode-locked semiconductor lasers subject to optical feedback: A semi-analytic approach

We propose a semi-analytical method of calculating the timing fluctuations in mode-locked semiconductor lasers and apply it to study the effect of delayed coherent optical feedback on pulse timing jitter in these lasers. The proposed method greatly reduces computation times and therefore allows for the investigation of the dependence of timing fluctuations over greater parameter domains. We show that resonant feedback leads to a reduction in the timing jitter and that a frequency-pulling region forms about the main resonances, within which a timing jitter reduction is observed. The width of these frequency-pulling regions increases linearly with short feedback delay times. We derive an analytic expression for the timing jitter, which predicts a monotonous decrease in the timing jitter for resonant feedback of increasing delay lengths, when timing jitter effects are fully separated from amplitude jitter effects. For long feedback cavities the decrease in timing jitter scales approximately as

Delayed feedback control of self-mobile cavity solitons

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Memory Effects in Population Dynamics : Spread of Infectious Disease as a Case Study

with the increase of the feedback delay time

Semiconductor mode-locked lasers with coherent dual-mode optical injection: simulations, analysis, and experiment

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Effect of dynamical instability on timing jitter in passively mode-locked quantum-dot lasers

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Dynamical regimes of a multistripe laser array with external off-axis feedback

Control of the motion of cavity solitons is one the central problems in nonlinear optical pattern formation. We report on the impact of the phase of the time-delayed optical feedback and carrier lifetime on the self-mobility of localized structures of light in broad-area semiconductor cavities. We show both analytically and numerically that the feedback phase strongly affects the drift instability threshold as well as the velocity of cavity soliton motion above this threshold. In addition we demonstrate that the noninstantaneous carrier response of the semiconductor medium is responsible for the increase of the critical feedback rate corresponding to the drift instability.

Bistable regimes in an optically injected mode-locked laser

Modification of behaviour in response to changes in the environment or ambient conditions, based on memory, is typical of the human and, possibly, many animal species.One obvious example of such adaptivity is, for instance, switching to a safer behaviour when in danger, from either a predator or an infectious disease. In human society such switching to safe behaviour is particularly apparent during epidemics. Mathematically, such changes of behaviour in response to changes in the ambient conditions can be described by models involving switching. In most cases, this switching is assumed to depend on the system state, and thus it disregards the history and, therefore, memory. Memory can be introduced into a mathematical model using a phenomenon known as hysteresis. We illustrate this idea using a simple SIR compartmental model that is applicable in epidemiology. Our goal is to show why and how hysteresis can arise in such a model, and how it may be applied to describe a variety of memory effects. Our other objective is to introduce a unified paradigm for mathematical modelling with memory effects in epidemiology and ecology. Our approach treats changing behaviour as an irreversible flow related to large ensembles of elementary exchange operations that recently has been successfully applied in a number of other areas, such as terrestrial hydrology, and macroeconomics. For the purposes of illustrating these ideas in an application to biology, we consider a rather simple case study and develop a model from first principles. We accompany the model with extensive numerical simulations which exhibit interesting qualitative effects.

Multi-stability and polariton solitons in microcavity wires

In this paper, we study the dynamics of a passively mode-locked semiconductor laser with dual-frequency coherent optical injection. The locking regions, where the laser pulse repetition rate is synchronized to the separation of the two injected frequencies, were calculated numerically using a delay differential equation model and measured experimentally. Asymptotic analysis performed in the limit of the small injection field amplitude revealed the dependence of the locking regions on the model parameters, such as optical bandwidth, absorber recovery time, and linear losses.