1,962 research outputs found
Quantum Exciton-Polariton Networks through Inverse Four-Wave Mixing
We demonstrate the potential of quantum operation using lattices of
exciton-polaritons in patterned semiconductor microcavities. By introducing an
inverse four-wave mixing scheme acting on localized modes, we show that it is
possible to develop non-classical correlations between individual condensates.
This allows a concept of quantum exciton-polariton networks, characterized by
the appearance of multimode entanglement even in the presence of realistic
levels of dissipation.Comment: 5 pages, 4 figures, pre-review version of manuscrip
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
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
An ECG-on-Chip with 535-nW/Channel Integrated Lossless Data Compressor for Wireless Sensors
This paper presents a low-power ECG recording system-on-chip (SoC) with
on-chip low-complexity lossless ECG compression for data reduction in
wireless/ambulatory ECG sensor devices. The chip uses a linear slope predictor
for data compression, and incorporates a novel low-complexity dynamic
coding-packaging scheme to frame the prediction error into fixed-length 16-bit
format. The proposed technique achieves an average compression ratio of 2.25x
on MIT/BIH ECG database. Implemented in a standard 0.35 um process, the
compressor uses 0.565K gates/channel occupying 0.4 mm2 for four channels, and
consumes 535 nW/channel at 2.4 V for ECG sampled at 512 Hz. Small size and
ultra-low power consumption makes the proposed technique suitable for wearable
ECG sensor applications
Spin-to-Orbital Angular Momentum Conversion in Semiconductor Microcavities
We experimentally demonstrate a technique for the generation of optical beams
carrying orbital angular momentum using a planar semiconductor microcavity.
Despite being isotropic systems, the transverse electric - transverse magnetic
(TE-TM) polarization splitting featured by semiconductor microcavities allows
for the conversion of the circular polarization of an incoming laser beam into
the orbital angular momentum of the transmitted light field. The process
implies the formation of topological entities, a pair of optical half-vortices,
in the intracavity field
Time-dependent integration of solar thermal technology in industrial processes
Solar energy is currently an underutilized renewable energy source that could fulfill low-temperature industrial heat demands with significant potential in high solar irradiance counties such as Malaysia. This study proposes a new systematic method for optimization of solar heat integration for different process options to minimize the levelized cost of heat by combining different methods from the literature. A case study from the literature is presented to demonstrate the proposed method combined with meteorological data in Malaysia. The method estimates capital cost and levelized cost of solar heating considering important physical constraints (e.g., available space) and recovery of waste heat. The method determines and optimizes important physical dimensions, including collector area, storage size, and control design. As the result of the case study, the solar thermal integration with Clean-In-Place streams (hot water) gives the lowest levelized cost of heat with RM 0.63/kWh (0.13 EUR/kWh) due to its lowest process temperature requirement. The sensitivity analysis indicates that collector price and collector efficiency are the critical parameters of solar thermal integration
Signature of the microcavity exciton-polariton relaxation mechanism in the polarization of emitted light
We have performed real and momentum space spin-dependent spectroscopy of
spontaneously formed exciton polariton condensates for a non-resonant pumping
scheme. Under linearly polarized pump, our results can be understood in terms
of spin-dependent Boltzmann equations in a two-state model. This suggests that
relaxation into the ground state occurs after multiple phonon scattering events
and only one polariton-polariton scattering. For the circular pumping case, in
which only excitons of one spin are injected, a bottleneck effect is observed,
implying inefficient relaxation.Comment: 7 pages, 7 figure
p-doped 1.3 μm InAs/GaAs quantum-dot laser with a low threshold current density and high differential efficiency
Amodification of the thickness of the low-growth- emperature component of the GaAs spacer layers in multilayer 1.3 um InAs/GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15 to 2 nm results in a reduced reverse bias leakage current and an increase in the
intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very low density of dislocated dots and a smaller number of defects in the thinner low-growth-temperature component of the GaAs spacer layer
Genomes of coral dinoflagellate symbionts highlight evolutionary adaptations conducive to a symbiotic lifestyle.
Despite half a century of research, the biology of dinoflagellates remains enigmatic: they defy many functional and genetic traits attributed to typical eukaryotic cells. Genomic approaches to study dinoflagellates are often stymied due to their large, multi-gigabase genomes. Members of the genus Symbiodinium are photosynthetic endosymbionts of stony corals that provide the foundation of coral reef ecosystems. Their smaller genome sizes provide an opportunity to interrogate evolution and functionality of dinoflagellate genomes and endosymbiosis. We sequenced the genome of the ancestral Symbiodinium microadriaticum and compared it to the genomes of the more derived Symbiodinium minutum and Symbiodinium kawagutii and eukaryote model systems as well as transcriptomes from other dinoflagellates. Comparative analyses of genome and transcriptome protein sets show that all dinoflagellates, not only Symbiodinium, possess significantly more transmembrane transporters involved in the exchange of amino acids, lipids, and glycerol than other eukaryotes. Importantly, we find that only Symbiodinium harbor an extensive transporter repertoire associated with the provisioning of carbon and nitrogen. Analyses of these transporters show species-specific expansions, which provides a genomic basis to explain differential compatibilities to an array of hosts and environments, and highlights the putative importance of gene duplications as an evolutionary mechanism in dinoflagellates and Symbiodinium
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