18,559 research outputs found
Soliton interaction in a fiber ring laser
We have experimentally investigated the soliton interaction in a passively
mode-locked fiber ring laser and revealed the existence of three types of
strong soliton interaction: a global type of soliton interaction caused by the
existence of unstable CW components; a local type of soliton interaction
mediated through the radiative dispersive waves; and the direct soliton
interaction. We found that the appearance of the various soliton operation
modes observed in the passively mode locked fiber soliton lasers are the direct
consequences of these three types of soliton interaction. The soliton
interaction in the laser is further numerically simulated based on a pulse
tracing technique. The numerical simulations confirmed the existence of the
dispersive wave mediated soliton interaction and the direct soliton
interaction. Furthermore, it was shown that the resonant dispersive waves
mediated soliton interaction in the laser always has the consequence of causing
random irregular relative soliton movement, and the experimentally observed
states of bound solitons are caused by the direct soliton interaction. In
particular, as the solitons generated in the laser could have a profile with
long tails, the direct soliton interaction could extend to a soliton separation
that is larger than 5 times of the soliton pulse width
Bound states of gain-guided solitons in a passively mode-locked fiber laser
We report on the observation of bound states of gain-guided solitons (GGSs)
in a dispersion-managed erbium-doped fiber laser operating in the normal net
cavity dispersion regime. Despite of the fact that the GGS is a chirped soliton
and there is strong pulse stretching and compression along the cavity in the
laser, the bound solitons observed have a fixed pulse separation, which is
invariant to the pump strength change. Numerical simulation confirmed the
experimental observations
Derangement Polynomials and Excedances of Type B
Adopting the definition of excedances of type B due to Brenti, we give a type
B analogue of the q-derangement polynomials. The connection between
q-derangement polynomials and Eulerian polynomials naturally extends to the
type B case. Based on this relation, we derive some basic properties of the
q-derangement polynomials of type B, including the generating function formula,
the Sturm sequence property, and the asymptotic normal distribution. We also
show that the q-derangement polynomials are almost symmetric in the sense that
the coefficients possess the spiral property.Comment: 18 page
Direct ultrashort pulse generation by intracavity nonlinear compression
Direct generation of ultrashort, transform-limited pulses in a laser
resonator is observed theoretically and experimentally. This constitutes a new
type of ultrashort pulse generation in mode-locked lasers: in contrast to the
well-known solitons (hyperbolic secant like), dispersion-managed solitons
(Gaussian-like), and parabolic pulses plus external compression, ultrashort
pulse solutions to the nonlinear wave equations that describe pulse evolution
in the laser cavity are observed. Stable ultrashort, transform-limited pulses
exist with optical spectrum broader than the gain bandwidth of the amplifier,
and this has practical application for other lasers
Bound states of dispersion-managed solitons in a fiber laser at near zero dispersion
We report on the observation of various bound states of dispersion-managed
(DM) solitons in a passively mode-locked Erbium-doped fiber ring laser at near
zero net cavity group velocity dispersion (GVD). The generated DM solitons are
characterized by their Gaussian-like spectral profile with no sidebands, which
is distinct from those of the conventional solitons generated in fiber lasers
with large net negative cavity GVD, of the parabolic pulses generated in fiber
lasers with positive cavity GVD and negligible gain saturation and bandwidth
limiting, and of the gain-guided solitons generated in fiber lasers with large
positive cavity GVD. Furthermore, bound states of DM solitons with fixed
soliton separations are also observed. We show that these bound solitons can
function as a unit to form bound states themselves. Numerical simulations
verified our experimental observations
Self-started unidirectional operation of a fiber ring soliton laser without an isolator
We demonstrate self-started mode-locking in an Erbium-doped fiber ring laser
by using the nonlinear polarization rotation mode-locking technique but without
an isolator in cavity. We show that due to the intrinsic effective nonlinearity
discrimination of the mode-locked pulse propagating along different cavity
directions, the soliton operation of the laser is always unidirectional, and
its features have no difference to that of the unidirectional lasers with an
isolator in cavity
Observation of high-order polarization-locked vector solitons in a fiber laser
We report on the experimental observation of a novel type of polarization
locked vector soliton in a passively mode-locked fiber laser. The vector
soliton is characterized by that not only the two orthogonally polarized
soliton components are phase locked, but also one of the components has a
double-humped intensity profile. Multiple such phase-locked high order vector
solitons with identical soliton parameters and harmonic mode-locking of the
vector solitons were also obtained in the laser. Numerical simulations
confirmed the existence of stable high-order vector solitons in fiber lasers.Comment: 15 pages,5 figures, Accepted by PR
Dark Pulse Emission of A Fiber Laser
We report on the dark pulse emission of an all-normal dispersion erbium-doped
fiber laser with a polarizer in cavity. We found experimentally that apart from
the bright pulse emission, under appropriate conditions the fiber laser could
also emit single or multiple dark pulses. Based on numerical simulations we
interpret the dark pulse formation in the laser as a result of dark soliton
shaping.Comment: 16 page
Dynamics in spinor condensates controlled by a microwave dressing field
We experimentally study spin dynamics in a sodium antiferromagnetic spinor
condensate with off-resonant microwave pulses. In contrast to a magnetic field,
a microwave dressing field enables us to explore rich spin dynamics under the
influence of a negative net quadratic Zeeman shift . We find an
experimental signature to determine the sign of , and observe
harmonic spin population oscillations at every except near each
separatrix in phase space where spin oscillation period diverges. In the
negative and positive regions, we also observe a remarkably
different relationship between each separatrix and the magnetization. Our data
confirms an important prediction derived from the mean-field theory:
spin-mixing dynamics in spin-1 condensates substantially depends on the sign of
the ratio of and the spin-dependent interaction energy. This work
may thus be the first to use only one atomic species to reveal mean-field spin
dynamics, especially the separatrix, which are predicted to appear differently
in spin-1 antiferromagnetic and ferromagnetic spinor condensates
Quantum quench and non-equilibrium dynamics in lattice-confined spinor condensates
We present an experimental study on non-equilibrium dynamics of a spinor
condensate after it is quenched across a superfluid to Mott insulator (MI)
phase transition in cubic lattices. Intricate dynamics consisting of
spin-mixing oscillations at multiple frequencies are observed in time
evolutions of the spinor condensate localized in deep lattices after the
quantum quench. Similar spin dynamics also appear after spinor gases in the MI
phase are suddenly moved away from their ground states via quenching magnetic
fields. We confirm these observed spectra of spin-mixing dynamics can be
utilized to reveal atom number distributions of an inhomogeneous system, and to
study transitions from two-body to many-body dynamics. Our data also imply the
non-equilibrium dynamics depend weakly on the quench speed but strongly on the
lattice potential. This enables precise measurements of the spin-dependent
interaction, a key parameter determining the spinor physics
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