40 research outputs found
Spectral Sidebands and Multi-Pulse Formation in Passively Mode Locked Lasers
Pulse formation in passively mode locked lasers is often accompanied with
dispersive waves that form of spectral sidebands due to spatial inhomogoneities
in the laser cavity. Here we present an explicit calculation of the amplitude,
frequency, and precise shape of the sidebands accompanying a soliton-like
pulse. We then extend the study to the global steady state of mode locked laser
with a variable number of pulses, and present experimental results in a mode
locked fiber laser that confirm the theory. The strong correlation between the
temporal width of the sidebands and the measured spacing between the pulses in
multipulse operation suggests that the sidebands have an important role in the
inter-pulse interaction.Comment: 6 pages, 5 figures, submitted to Phys. Rev.
Haus/Gross-Pitaevskii equation for random lasers
We report on experimental tests of the trend of random laserlinewidth versus
pumping power as predicted by an Haus master equation that is formally
identical to the one-dimensional Gross- Pitaevskii equation in an harmonic
potential. Experiments are done by employing picosecond pumped dispersions of
Titaniumdioxide particles in dye-doped methanol. The derivation of the master
equations is also detailed and shown to be in agreement with experiments
analytically predicting the value of the threshold linewidth
Dynamical models for dissipative localized waves of the complex Ginzburg-Landau equation
Finite-dimensional dynamical models for solitons of the cubic-quintic complex Ginzburg-Landau equation
CGLE are derived. The models describe the evolution of the pulse parameters, such as the maximum
amplitude, pulse width, and chirp. A clear correspondence between attractors of the finite-dimensional dynamical
systems and localized waves of the continuous dissipative system is demonstrated. It is shown that stationary
solitons of the CGLE correspond to fixed points, while pulsating solitons are associated with stable limit
cycles. The models show that a transformation from a stationary soliton to a pulsating soliton is the result of
a Hopf bifurcation in the reduced dynamical system. The appearance of moving fronts kinks in the CGLE is
related to the loss of stability of the limit cycles. Bifurcation boundaries and pulse behavior in the regions
between the boundaries, for a wide range of system parameters, are found from analysis of the reduced
dynamical models. We also provide a comparison between various models and their correspondence to the
exact results
Pinned modes in two-dimensional lossy lattices with local gain and nonlinearity
We introduce a system with one or two amplified nonlinear sites ("hot spots",
HSs) embedded into a two-dimensional linear lossy lattice. The system describes
an array of evanescently coupled optical or plasmonic waveguides, with gain
applied at selected HS cores. The subject of the analysis is discrete solitons
pinned to the HSs. The shape of the localized modes is found in
quasi-analytical and numerical forms, using a truncated lattice for the
analytical consideration. Stability eigenvalues are computed numerically, and
the results are supplemented by direct numerical simulations. In the case of
self-focusing nonlinearity, the modes pinned to a single HS are stable or
unstable when the nonlinearity includes the cubic loss or gain, respectively.
If the nonlinearity is self-defocusing, the unsaturated cubic gain acting at
the HS supports stable modes in a small parametric area, while weak cubic loss
gives rise to a bistability of the discrete solitons. Symmetric and
antisymmetric modes pinned to a symmetric set of two HSs are considered too.Comment: Philosophical Transactions of the Royal Society A, in press (a
special issue on "Localized structures in dissipative media"