121 research outputs found
Temporal solitons in an optically injected Kerr cavity with two spectral filters
We investigate theoretically the dynamical behavior of an optically injected Kerr cavity where the chromatic dispersion is induced by propagation of light through two Lorentzian spectral filters with different widths and central frequencies. We show that this setup can be modeled by a second order delay differential equation that can be considered as a generalization of the Ikeda map with included spectral filtering, dispersion, and coherent injection terms. We demonstrate that this equation can exhibit modulational instability and bright localized structures formation in the anomalous dispersion regime
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Dynamics of an inhomogeneously broadened passively mode-locked laser
We study theoretically the effect of inhomogeneous broadening of the
gain and absorption lines on the dynamics of a passively mode-locked laser.
We demonstrate numerically using travelling wave equations the formation of a
Lamb-dip instability and suppression of Q-switching in a laser with large
inhomogeneous broadening. We derive simplified delay-differential equation
model for a mode-locked laser with inhomogeneously broadened gain and
absorption lines and perform numerical bifurcation analysis of this model
Dynamics of an inhomogeneously broadened passively mode-locked laser
We study theoretically the effect of inhomogeneous broadening of the gain and absorption lines on the dynamics of a passively mode-locked laser. We demonstrate numerically using travelling wave equations the formation of a Lamb-dip instability and suppression of Q-switching in a laser with large inhomogeneous broadening. We derive simplified delay-differential equation model for a mode-locked laser with inhomogeneously broadened gain and absorption lines and perform numerical bifurcation analysis of this model
Negative refraction in natural ferromagnetic metals
It is generally believed that Veselago's criterion for negative refraction
cannot be fulfilled in natural materials. However, considering imaginary parts
of the permittivity ({\epsilon}) and permeability ({\mu}) and for metals at not
too high frequencies the general condition for negative refraction becomes
extremely simple: Re({\mu}) Re(n) < 0. Here we demonstrate
experimentally that in such natural metals as pure Co and FeCo alloy the
negative values of the refractive index are achieved close to the frequency of
the ferromagnetic resonance. Large values of the negative refraction can be
obtained at room temperature and they can easily be tuned in moderate magnetic
fields
Adaptive behaviour in a predator-prey model leads to multiple equilibrium states
There is evidence that multiple stable equilibrium states are possible in real-life ecological systems. In order to verify a hypothesis that such a multitude of equilibrium states can be caused by adapting of animal behaviour to changes of environmental conditions, we consider a simple predator-prey model where prey changes a mode of behaviour in response to the pressure of predation. This model exhibits two stable coexisting equilibrium states with basins of attraction separated by a separatrix of a saddle point
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Bifurcations in a model of monolithic passively mode-locked semiconductior 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 harmonic mode-locking regime with two
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
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Adaptive behaviour in a predator-prey model leads to multiple equilibrium states
There is evidence that multiple stable equilibrium states are possible
in real-life ecological systems. In order to verify a hypothesis that such a
multitude of equilibrium states can be caused by adapting of animal behaviour
to changes of environmental conditions, we consider a simple predator-prey
model where prey changes a mode of behaviour in response to the pressure of
predation. This model exhibits two stable coexisting equilibrium states with
basins of attraction separated by a separatrix of a saddle point
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 with the increase of the feedback delay time
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