7,398 research outputs found
Vortex-vortex control in exciton-polariton condensates
Full text linkVortices 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
Full text linkVortices 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
Structuring co- and counter-flowing currents of polariton condensates in concentric ring-shaped potentials
Full text linkWe investigate the current flow of microcavity polariton condensates loaded
into concentric ring-shaped potentials. The tunneling of the condensates
between different potential rings results in different phase-locked states,
depending on the separation of the potential rings. As a consequence, the
condensate currents in different rings can flow either in the same or opposite
direction depending on the specific configuration of the ring-shaped
potentials. In two concentric standard ring-shaped potentials, the condensates
always circulate in the same direction (co-flowing current) and the vortices
formed in the two rings share the same topological charge because of the
azimuthally uniform distribution of their phase difference. In this case,
increasing the number of the potential rings enables the excitation of
Bessel-like solutions. If the two ring-shaped potentials are engineered into an
eye shape with the inner ring being standard ring-shaped and the outer ring
being elliptically ring-shaped, the phase differences of the condensates in the
two rings along the major and minor axes of the ellipse can be opposite, which
gives rise to a counter-flowing condensate currents
Spiraling vortices in exciton-polariton condensates
Get PDFWe introduce the phenomenon of spiraling vortices in driven-dissipative
(non-equilibrium) exciton-polariton condensates excited by a non-resonant pump
beam. At suitable low pump intensities, these vortices are shown to spiral
along circular trajectories whose diameter is inversely proportional to the
effective mass of the polaritons, while the rotation period is mass
independent. Both diameter and rotation period are inversely proportional to
the pump intensity. Stable spiraling patterns in the form of complexes of
multiple mutually-interacting vortices are also found. At elevated pump
intensities, which create a stronger homogeneous background, we observe more
complex vortex trajectories resembling Spirograph patterns
Modular Nucleic Acid Assembled p/MHC Microarrays for Multiplexed Sorting of Antigen-Specific T Cells
Get PDFThe human immune system consists of a large number of T cells capable of recognizing and responding to antigens derived from various sources. The development of peptide-major histocompatibility (p/MHC) tetrameric complexes has enabled the direct detection of these antigen-specific T cells. With the goal of increasing throughput and multiplexing of T cell detection, protein microarrays spotted with defined p/MHC complexes have been reported, but studies have been limited due to the inherent instability and reproducibility of arrays produced via conventional spotted methods. Herein, we report on a platform for the detection of antigen-specific T cells on glass substrates that offers significant advantages over existing surface-bound schemes. In this approach, called “Nucleic Acid Cell Sorting (NACS)”, single-stranded DNA oligomers conjugated site-specifically to p/MHC tetramers are employed to immobilize p/MHC tetramers via hybridization to a complementary-printed substrate. Fully assembled p/MHC arrays are used to detect and enumerate T cells captured from cellular suspensions, including primary human T cells collected from cancer patients. NACS arrays outperform conventional spotted arrays assessed in key criteria such as repeatability and homogeneity. The versatility of employing DNA sequences for cell sorting is exploited to enable the programmed, selective release of target populations of immobilized T cells with restriction endonucleases for downstream analysis. Because of the performance, facile and modular assembly of p/MHC tetramer arrays, NACS holds promise as a versatile platform for multiplexed T cell detection
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