2,838 research outputs found
Exciton-Polariton Oscillations in Real Space
We introduce and model spin-Rabi oscillations based on exciton-polaritons in
semiconductor microcavities. The phase and polarization of oscillations can be
controlled by resonant coherent pulses and the propagation of oscillating
domains gives rise to phase-dependent interference patterns in real space. We
show that interbranch polariton-polariton scattering controls the propagation
of oscillating domains, which can be used to realize logic gates based on an
analogue variable phase.Comment: 6 page
Stochastic Gross-Pitaevskii Equation for the Dynamical Thermalization of Bose-Einstein Condensates
We present a theory for the description of energy relaxation in a
nonequilibrium condensate of bosonic particles. The approach is based on
coupling to a thermal bath of other particles (e.g., phonons in a crystal, or
noncondensed atoms in a cold atom system), which are treated with a Monte Carlo
type approach. Together with a full account of particle-particle interactions,
dynamic driving, and particle loss, this offers a complete description of
recent experiments in which Bose-Einstein condensates are seen to relax their
energy as they propagate in real space and time. As an example, we apply the
theory to the solid-state system of microcavity exciton polaritons, in which
nonequilibrium effects are particularly prominent.Comment: Manuscript: 5 pages (Main Text) + 2 figures + 4 pages (Supplemental
Material). Proofs versio
Incoherent excitation and switching of spin states in exciton-polariton condensates
We investigate, theoretically and numerically, the spin dynamics of a
two-component exciton-polariton condensate created and sustained by
non-resonant spin-polarized optical pumping of a semiconductor microcavity.
Using the open-dissipative mean-field model, we show that the existence of well
defined phase-locked steady states of the condensate may lead to efficient
switching and control of spin (polarization) states with a non-resonant
excitation. Spatially inhomogeneous pulsed excitations can cause symmetry
breaking in the pseudo-spin structure of the condensate and lead to formation
of non-trivial spin textures. Our model is universally applicable to two weakly
coupled polariton condensates, and therefore can also describe the behaviour of
condensate populations and phases in 'double-well' type potentials
The Design for a Nanoscale Single-Photon Spin Splitter
We propose using the effective spin-orbit interaction of light in
Bragg-modulated cylindrical waveguides for the effcient separation of spin-up
and spin-down photons emitted by a single photon emitter. Due to the spin and
directional dependence of photonic stopbands in the waveguides, spin-up (down)
photon propagation in the negative (positive) direction along the waveguide
axis is blocked while the same photon freely propagates in the opposite
direction.Comment: 5 pages, 3 figure
Nonlinear Effects in Multi-Photon Polaritonics
We consider theoretically nonlinear effects in a semiconductor quantum well
embedded inside a photonic microcavity. Two-photon absorption by a 2p exciton
state is considered and investigated; the matrix element of two-photon
absorption is calculated. We compute the emission spectrum of the sample and
demonstrate that under coherent pumping the nonlinearity of the two photon
absorption process gives rise to bistability.Comment: Accepted to Optics Express, 7 main pages + 3 figures + supplement
Spontaneous polariton currents in periodic lateral chains
We predict spontaneous generation of superfluid polariton currents in planar
microcavities with lateral periodic modulation of both potential and decay
rate. A spontaneous breaking of spatial inversion symmetry of a polariton
condensate emerges at a critical pumping, and the current direction is
stochastically chosen. We analyse the stability of the current with respect to
the fluctuations of the condensate. A peculiar spatial current domain structure
emerges, where the current direction is switched at the domain walls, and the
characteristic domain size and lifetime scale with the pumping power.Comment: 6+6 pages, 4+1 figures (with supplemental material
Monolithic Arrays of Grating-Surface-Emitting Diode Lasers and Quantum Well Modulators for Optical Communications
The electro-optic switching properties of injection-coupled coherent 2-D grating-surface-emitting laser arrays with multiple gain sections and quantum well active layers are discussed and demonstrated. Within such an array of injection-coupled grating-surface-emitting lasers, a single gain section can be operated as intra-cavity saturable loss element that can modulate the output of the entire array. Experimental results demonstrate efficient sub-nanosecond switching of high power grading-surface-emitting laser arrays by using only one gain section as an intra-cavity loss modulator
Stochastic polarization formation in exciton-polariton Bose-Einstein condensates
We demonstrate theoretically the spontaneous formation of a stochastic
polarization in exciton-polariton Bose-Einstein condensates in planar
microcavities under pulsed excitation. Below the threshold pumping intensity
(dependent on the polariton life-time) the average polarization degree is close
to zero, whilst above threshold the condensate acquires a polarization
described by a (pseudospin) vector with random orientation, in general. We
establish the link between second order coherence of the polariton condensate
and the distribution function of its polarization. We examine also the
mechanisms of polarization dephasing and relaxation.Comment: 4 pages, 3 figure
Optical control of spin textures in quasi-one-dimensional polariton condensates
We investigate, through polarization-resolved spectroscopy, the spin
transport by propagating polariton condensates in a quasi one-dimensional
microcavity ridge along macroscopic distances. Under circularly polarized,
continuous-wave, non-resonant excitation, a sinusoidal precession of the spin
in real space is observed, whose phase depends on the emission energy. The
experiments are compared with simulations of the spinor-polariton condensate
dynamics based on a generalized Gross-Pitaevskii equation, modified to account
for incoherent pumping, decay and energy relaxation within the condensate.Comment: 10 pages, 9 figure
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