Ultrafast tristable spin memory of a coherent polariton gas (original) (raw)
Related papers
A Room-temperature Ultrafast Spin-polarized Polariton Laser
Light-matter interactions are greatly altered in resonators and heterostructures where both electrons and photons are confined. These interactions lead to nonlinear optical processes and lasing where both photon mode control and electron quantum confinement play a role. Lasing in semiconductors is generally independent of the spins of electrons and holes, which constitute the gain medium. However, in a few spin-controlled lasers 1-5 , spin-polarized carriers with long spin relaxation times (1 ns) result in continuous or sub-nanosecond pulsed circularly polarized stimulated emission. In principle, optical or electrical injection of spinpolarized carriers can reduce the lasing threshold 6 and switching time 7. Here, we demonstrate room-temperature spin-polarized ultrafast (sub-10-ps) pulsed lasing in a highly optically excited GaAs microcavity embedded with InGaAs multiple quantum wells (MQWs) within which the spin relaxation time is less than 10 ps. The polariton laser produces fully circularly polarized radiation. By suppressing the steady-state thermal heating and tuning the MQW bandgap to the cavity resonance, we obtain a lasing efficiency greater than 10%, matching the fraction of carriers photoexcited in the MQWs. Our results provide insights into Coulomb many-body effects in light-matter hybrids 8-12 .
Nonresonant optical control of a spinor polariton condensate
Physical Review B, 2016
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.
Influence of a nonradiative reservoir on polariton spin multistability
Physical Review B, 2013
Since its prediction by NA Gippius et al. 1 in 2007, polariton spin multistability rapidly appeared as a very promising phenomenon to realize spin-based optoelectronics devices with microcavity polaritons. Several proposals have shown the exceptional potential of this effect to realize spin memories 2 and polariton spintronic circuits. 3 In a recent work, we demonstrated experimentally spin multistability with a single macroscopically occupied polariton level in a microcavity with patterned traps. 4 Moreover, we evidenced the spin ...
Exciton–polariton spin switches
Nature Photonics, 2010
Integrated switching devices comprise the building blocks of ultrafast optical signal processing 1,2 . As the next stage following intensity switching 1,3,4 , circular polarization switches are attracting considerable interest because of their applications in spin-based architectures 10 . 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 11,12 , fast operation 13 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 14 .
Optical Bistability under Nonresonant Excitation in Spinor Polariton Condensates
Physical Review Letters, 2018
We realise bistability in the spinor of polariton condensates under non-resonant optical excitation and in the absence of biasing external fields. Numerical modelling of the system using the Ginzburg-Landau equation with an internal Josephson coupling between the two spin components of the condensate qualitatively describes the experimental observations. We demonstrate that polariton spin bistability persists for sweep times in the range of [10µsec, 1sec] offering a promising route to spin switches and spin memory elements.
High-speed switching of spin polarization for proposed spin-photon memory
Applied Physics Letters, 2009
Nonvolatile high-speed optical memory is proposed, which utilizes the magnetization reversal of nanomagnet by spin-polarized photoexcited electrons. It was demonstrated experimentally that one selected pulse from the train of two optical data pulses with interval of 450 fs can solely excite the spin-polarized electrons without a disturbance from the unselected optical data pulse. That proves feasibility for operation of the memory with speed of 2.2 Tbits/s.
We use one single, few-picosecond-long, variably polarized laser pulse to deterministically write any selected spin state of a quantum dot confined dark exciton whose life and coherence time are six and five orders of magnitude longer than the laser pulse duration, respectively. The pulse is tuned to an absorption resonance of an excited dark exciton state, which acquires non-negligible oscillator strength due to residual mixing with bright exciton states. We obtain a high fidelity one-to-one mapping from any point on the Poincaré sphere of the pulse polarization to a corresponding point on the Bloch sphere of the spin of the deterministically photogenerated dark exciton.
physica status solidi (c), 2006
A new model for rigorous theoretical description of circularly (elliptically) polarised ultrashort optical pulse interactions with the resonant nonlinearities in semiconductor optical waveguides is proposed. The method is based on self-consistent solution in the time domain of the vector Maxwell equations coupled via microscopic polarisation to the coherent time-evolution equations of a discrete N-level quantum system in terms of the real pseudospin (coherence) vector. The model is initially applied to a generic twolevel quantum system and subsequently to a 4-level system describing the heavy-hole excitonic transitions in low-dimensional semiconductor systems, such as quantum wells and quantum dots. Selective optical excitation of specific spin states by predefined helicity of the optical field in the linear regime and an onset of self-induced transparency and polarised soliton formation in the nonlinear regime are numerically demonstrated in both discrete-level systems.
Towards ultrafast spin-state switching in the solid state
Comptes Rendus Chimie, 2008
We report here on the photo-switching dynamics of a Fe(III) molecular material undergoing a spin-crossover. The thermal spin conversion is observed by magnetic and spectroscopic measurements, as well as imaging. The photoinduced switching dynamics between the low-spin and the high-spin states is studied with a femtosecond optical pumpeprobe technique. The results demonstrate that the switching occurs within a timescale shorter than one picosecond. To cite this article: N.