1,720,998 research outputs found
Optical circuits based on polariton neurons in semiconductor microcavities
Full text linkBy exploiting the polarization multistability of polaritons, we show that polarized signals can be conducted in the plane of a semiconductor microcavity along controlled channels or “neurons.” Furthermore, because of the interaction of polaritons with opposite spins it is possible to realize binary logic gates operating on the polarization degree of freedom. Multiple gates can be integrated together to form an optical circuit contained in a single semiconductor microcavity
Spin rings in semiconductor microcavities
No full textNew effects of self-organization and polarization pattern formation in semiconductor microcavities, operating in the nonlinear regime, are predicted and theoretically analyzed. We show that a spatially inhomogeneous elliptically polarized optical cw pump leads to the formation of a strongly circularly polarized ring in real space. This effect is due to the polarization multistability of cavity polaritons which was recently predicted. The possible switching between different stable configurations allows the realization of a localized spin memory element, suitable for an optical data storage device
Generation and dynamics of vortex lattices in coherent exciton-polariton fields
Full text linkVortex dynamics in coherent ensembles of exciton polaritons (condensates) is studied in the framework of the polarization-dependent Gross-Pitaevskii equation. Vortex lattices can be resonantly excited in the polariton field by the interference of three or more optical pumps. Vortex-antivortex pairs can also appear in polariton condensates due to scattering with disorder. The nonlinear vortex dynamics is characterized by interactions of vortex cores and vortex-antivortex recombination
Optically induced transparency in bosonic cascade lasers
No full textBosonic cascade lasers are terahertz (THz) lasers based on stimulated radiative transitions between bosonic condensates of excitons or exciton–polaritons confined in a trap. We study the interaction of an incoming THz pulse resonant in frequency with the transitions between neighboring energy levels of the cascade. We show that at certain optical pump conditions the cascade becomes transparent to the incident pulse: it neither absorbs nor amplifies it in the mean-field approximation. The populations of intermediate levels of the bosonic cascade change as the THz pulse passes, nevertheless. In comparison, a fermionic cascade laser does not reveal any of these properties.</p
Spontaneous and superfluid chiral edge states in exciton-polariton condensates
No full textWe present a scheme of interaction-induced topological band structures based on the spin anisotropy of exciton-polaritons in semiconductor microcavities. We predict theoretically that this scheme allows the engineering of topological gaps, without requiring a magnetic field or strong spin-orbit interaction (transverse electric-transverse magnetic splitting). Under nonresonant pumping we find that an initially topologically trivial system undergoes a topological transition upon the spontaneous breaking of phase symmetry associated with polariton condensation. Under either nonresonant or resonant coherent pumping we find that it is also possible to engineer a topological dispersion that is linear in wave vector—a property associated with polariton superfluidity
Non-resonant optical control of a spinor polariton condensate
No full textWe investigate the spin dynamics of polariton condensates spatially separated from and effectively confined by the pumping exciton reservoir. We obtain a strong correlation between the ellipticity of the non-resonant optical pump and the degree of circular polarisation (DCP) of the condensate at the onset of condensation. With increasing excitation density we observe a reversal of the DCP. The spin dynamics of the trapped condensate are described within the framework of the spinor complex Ginzburg-Landau equations in the Josephson regime, where the dynamics of the system are reduced to a current-driven Josephson junction. We show that the observed spin reversal is due to the interplay between an internal Josephson coupling effect and the detuning of the two projections of the spinor condensate via transition from a synchronised to a desynchronised regime. These results suggest that spinor polariton condensates can be controlled by tuning the non-resonant excitation density offering applications in electrically pumped polariton spin switches
Dataset for Non-resonant optical control of a spinor polariton condensate
No full textDataset supports:
Askitopoulos, Alexis et al (2016) Non-resonant optical control of a spinor polariton condensate. Physical Review B.
We investigate the spin dynamics of polariton condensates spatially separated from and effectively confined by the pumping exciton reservoir. We obtain a strong correlation between the ellipticity of the non-resonant optical pump and the degree of circular polarisation (DCP) of the condensate at the onset of condensation. With increasing excitation density we observe a reversal of the DCP. The spin dynamics of the trapped condensate are described within the framework of the spinor complex Ginzburg-Landau equations in the Josephson regime, where the dynamics of the system are reduced to a current-driven Josephson junction. We show that the observed spin reversal is due to the interplay between an internal Josephson coupling effect and the detuning of the two projections of the spinor condensate via transition from a synchronised to a desynchronised regime. These results suggest that spinor polariton condensates can be controlled by tuning the non-resonant excitation density offering applications in electrically pumped polariton spin switches.</span
Probabilistic solving of NP-hard problems with bistable nonlinear optical networks
Full text linkWe study theoretically a lattice of locally bistable driven-dissipative nonlinear cavities. The system is found to resemble the classical Ising model and enables its effective simulation. First, we benchmark the performance of driven-dissipative nonlinear cavities for spin-glass problems, and study the scaling of the ground-state-energy deviation and success probability as a function of system size. Next, we show how an effective bias field can be included in an optical model and use it for probabilistic solving of optimization problems. As particular examples we consider NP-hard problems embedded in the Ising model, namely graph partitioning and the knapsack problem. Finally, we confirm that locally bistable polariton networks act as classical optimizers and can potentially provide an improvement within the exponential complexity class
Letter abstract. Exciton-polariton spin switches
No full textIntegrated switching devices comprise the building blocks of ultrafast optical signal processing. As the next stage following intensity switching circular polarization switches are attracting considerable interest because of their applications in spin-based architectures. They usually take advantage of nonlinear optical effects, and require high powers and external optical elements. Semiconductor microcavities provide a significant step forward due to their low-threshold, polarization-dependent, nonlinear emission, fast operation and integrability. Here, we demonstrate a non-local, all-optical spin switch based on exciton–polaritons in a semiconductor microcavity. In the presence of a sub-threshold pump laser (dark regime), a tightly localized probe induces the switch-on of the entire pumped area. If the pump is circularly polarized, the switch is conditional on the polarization of the probe, but if it is linearly polarized, a circularly polarized probe fully determines the final polarization of the pumped area. These results set the basis for the development of spin-based logic devices, integrated in a chip
An exciton-polariton bolometer for terahertz radiation detection
No full textWe experimentally investigate the feasibility of a bolometric device based on exciton-polaritons. Initial measurements presented in this work show that heating - via thermal expansion and bandgap renormalization - modifies the exciton-polariton propagation wavevector making exciton-polaritons propagation remarkably sensitive to thermal variations. By theoretical simulations we predict that using a single layer graphene absorbing layer, a THz bolometric sensor can be realized by a simple exciton-polariton ring interferometer device. The predicted sensitivity is comparable to presently existing THz bolometric devices with the convenience of being a device that inherently produces an optical signal output.</p
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