30 research outputs found
Lasing threshold doubling at the crossover from strong to weak coupling regime in GaAs microcavity
In a polariton, laser coherent monochromatic light is produced by a low-energy state of the system at the bottom of a polariton ‘trap’, where a condensate of polaritons is formed, requiring no conventional population inversion. Following the recent realization of polariton light-emitting diodes (LEDs) based on GaAs microcavities (MCs) operating up to room temperature, efforts have been directed towards the demonstration of an electrically injected polariton laser. However, until now, low-threshold polariton lasing in GaAs MCs under optical pumping has been reported only at low temperatures. Here, we investigate the temperature dependence of lasing threshold across the border of the strong-to-weak coupling regime transition in high-finesse GaAs MCs under non-resonant optical pumping. Remarkably, we find that although lasing in the strong coupling regime is lost when the temperature is raised from 25 to 70 K, the threshold only doubles, in stark contrast with the expected difference of two orders of magnitude. Our results can be explained by considering temperatureinduced thermalization of carriers to high wavevector states, increasing the reservoir’s overall carrier lifetime, resulting in an order of magnitude higher steady-state carrier density at 70 K under similar pumping conditions
Hybrid organic-inorganic polariton laser
Organic materials exhibit exceptional room temperature light emitting characteristics and enormous exciton oscillator strength, however, their low charge carrier mobility prevent their use in high-performance applications such as electrically pumped lasers. In this context, ultralow threshold polariton lasers, whose operation relies on Bose-Einstein condensation of polaritons - part-light part-matter quasiparticles, are highly advantageous since the requirement for high carrier injection no longer holds. Polariton lasers have been successfully implemented using inorganic materials owing to their excellent electrical properties, however, in most cases their relatively small exciton binding energies limit their operation temperature. It has been suggested that combining organic and inorganic semiconductors in a hybrid microcavity, exploiting resonant interactions between these materials would permit to dramatically enhance optical nonlinearities and operation temperature. Here, we obtain cavity mediated hybridization of GaAs and J-aggregate excitons in the strong coupling regime under electrical injection of carriers as well as polariton lasing up to 200 K under non-resonant optical pumping. Our demonstration paves the way towards realization of hybrid organic-inorganic microcavities which utilise the organic component for sustaining high temperature polariton condensation and efficient electrical injection through inorganic structure
Spin selective filtering of polariton condensate flow
Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization
Dynamics of a polariton condensate transistor switch
We present a time-resolved study of the logical operation of a polariton condensate transistor switch.
Creating a polariton condensate (source) in a GaAs ridge-shaped microcavity with a non-resonant pulsed laser beam, the polariton propagation towards a collector, at the ridge edge, is controlled by a
second weak pulse (gate), located between the source and the collector. The experimental results are
interpreted in the light of simulations based on the generalized Gross-Pitaevskii equation, including
incoherent pumping, decay, and energy relaxation within the condensate
Steady states of a chi-three parametric oscillator with coupled polarisations
Polarisation effects in the microcavity parametric oscillator are studied
using a simple model in which two chi-three optical parametric oscillators are
coupled together. It is found that there are, in general, a number of steady
states of the model under continuous pumping. There are both continuous and
discontinuous thresholds, at which new steady-states appear as the driving
intensity is increased: at the continuous thresholds, the new state has zero
output intensity, whereas at the discontinuous threshold it has a finite output
intensity. The discontinuous thresholds have no analog in the uncoupled device.
The coupling also generates rotations of the linear polarisation of the output
compared with the pump, and shifts in the output frequencies as the driving
polarisation or intensity is varied. For large ratios of the interaction
between polarisations to the interaction within polarisations, of the order of
5, one of the thresholds has its lowest value when the pump is elliptically
polarised. This is consistent with recent experiments in which the maximum
output was achieved with an elliptically polarised pump.Comment: 7 pages, 4 figure
Many-body physics of a quantum fluid of exciton-polaritons in a semiconductor microcavity
Some recent results concerning nonlinear optics in semiconductor
microcavities are reviewed from the point of view of the many-body physics of
an interacting photon gas. Analogies with systems of cold atoms at thermal
equilibrium are drawn, and the peculiar behaviours due to the non-equilibrium
regime pointed out. The richness of the predicted behaviours shows the
potentialities of optical systems for the study of the physics of quantum
fluids.Comment: Proceedings of QFS2006 conference to appear on JLT
Polariton condensation and lasing in optical microcavities - the decoherence driven crossover
We explore the behaviour of a system which consists of a photon mode dipole
coupled to a medium of two-level oscillators in a microcavity in the presence
of decoherence. We consider two types of decoherence processes which are
analogous to magnetic and non-magnetic impurities in superconductors. We study
different phases of this system as the decoherence strength and the excitation
density is changed. For a low decoherence we obtain a polariton condensate with
comparable excitonic and photonic parts at low densities and a BCS-like state
with bigger photon component due to the fermionic phase space filling effect at
high densities. In both cases there is a large gap in the density of states. As
the decoherence is increased the gap is broadened and suppressed, resulting in
a gapless condensate and finally a suppression of the coherence in a low
density regime and a laser at high density limit. A crossover between these
regimes is studied in a self-consistent way analogous to the Abrikosov and
Gor'kov theory of gapless superconductivity.Comment: 17 pages, 8 figures, submitted to PR
Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms
Experimental and numerical investigation of single-beam and pump-probe
interaction with a resonantly absorbing dense extended medium under strong and
weak field-matter coupling is presented. Significant probe beam amplification
and conical emission were observed. Under relatively weak pumping and high
medium density, when the condition of strong coupling between field and
resonant matter is fulfilled, the probe amplification spectrum has a form of
spectral doublet. Stronger pumping leads to the appearance of a single peak of
the probe beam amplification at the transition frequency. The greater probe
intensity results in an asymmetrical transmission spectrum with amplification
at the blue wing of the absorption line and attenuation at the red one. Under
high medium density, a broad band of amplification appears. Theoretical model
is based on the solution of the Maxwell-Bloch equations for a two-level system.
Different types of probe transmission spectra obtained are attributed to
complex dynamics of a coherent medium response to broadband polychromatic
radiation of a multimode dye laser.Comment: 9 pages, 13 figures, corrected, Fig.8 was changed, to be published in
Phys. Rev.
Polariton quantization modes and whispering gallery modes in a cylindrical microcavity
International audienc
Ä°BN MÄ°SKEVEYH'Ä°N ADALET ANLAYIÅžI
Strongly angular-dependent emission properties are observed from a semiconductor microcavity pumped along a critical angle of incidence. In contrast to the luminescence from conventional semiconductor heterostructures, the emission is completely asymmetrical with respect to the sample normal. The results imply that parametric scattering dominates the energy relaxation of polaritons, and is enhanced by the deformed shape of the dispersion relations