1,013 research outputs found
Vortex-vortex control in exciton-polariton condensates
Vortices are widely studied in fields ranging from nonlinear optics to
magnetic systems and superconductors. A vortex carries a binary information
corresponding to its topological charge, `plus' or `minus', that can be used
for information storage and processing. In spatially extended optical and
condensed many-particle systems, achieving full control over vortex formation
and its charge is particularly difficult and is not easily extended to systems
of multiple vortices. Here we demonstrate the optical creation of multiplets of
phase-locked vortices in polariton condensates using off-resonant excitation
with ring-shaped pump beams. We find that the vorticity of one vortex can be
controlled solely using the phase-locking with other nearby vortices. Using
this mechanism, we demonstrate how an existing vortex with a specific
topological charge can be inverted to the oppositely charged state, and how the
charge state of one reference vortex can be copied to a neighboring vortex.
This way we can optically encode any set of binary information onto a chain of
vortices. We further show that this information can be modified later by using
the possibility to address and manipulate each vortex in the chain
individually.Comment: Physical Review B, in pres
Circular polarization reversal of half-vortex cores in polariton condensates
Vortices are topological objects carrying quantized orbital angular momentum
and have been widely studied in many physical systems for their applicability
in information storage and processing. In systems with spin degree of freedom
the elementary excitations are so called half-vortices, carrying a quantum
rotation only in one of the two spin components. We study the spontaneous
formation and stability of localized such half-vortices in semiconductor
microcavity polariton condensates, non-resonantly excited by a linearly
polarized ring-shaped pump. The TE-TM splitting of optical modes in the
microcavity system leads to an effective spin-orbit coupling, resulting in
solutions with discrete rotational symmetry. The cross-interaction between
different spin components provides an efficient method to realize all-optical
half-vortex core switching inverting its circular polarization state. This
switching can be directly measured in the polarization resolved intensity in
the vortex core region and it can also be applied to higher order half-vortex
states.Comment: 8 pages, 8 figure
Externally Controlled Lotka-Volterra Dynamics in a Linearly Polarized Polariton Fluid
Spontaneous formation of transverse patterns is ubiquitous in nonlinear
dynamical systems of all kinds. An aspect of particular interest is the active
control of such patterns. In nonlinear optical systems this can be used for
all-optical switching with transistor-like performance, for example realized
with polaritons in a planar quantum-well semiconductor microcavity. Here we
focus on a specific configuration which takes advantage of the intricate
polarization dependencies in the interacting optically driven polariton system.
Besides detailed numerical simulations of the coupled light-field exciton
dynamics, in the present paper we focus on the derivation of a simplified
population competition model giving detailed insight into the underlying
mechanisms from a nonlinear dynamical systems perspective. We show that such a
model takes the form of a generalized Lotka-Volterra system for two competing
populations explicitly including a source term that enables external control.
We present a comprehensive analysis both of the existence and stability of
stationary states in the parameter space spanned by spatial anisotropy and
external control strength. We also construct phase boundaries in non-trivial
regions and characterize emerging bifurcations. The population competition
model reproduces all key features of the switching observed in full numerical
simulations of the rather complex semiconductor system and at the same time is
simple enough for a fully analytical understanding of the system dynamics.Comment: 11 pages, 8 figure
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