arXiv subjects

H. Flayac

Publications and source records attributed to H. Flayac.

At least 19 recordsLinked to original sources

arXiv2019

Counter-directional polariton coupler

We report on an on-chip routing device for propagating condensates of exciton-polaritons. This counterdirectional coupler implements signal control by a photonic microdisk potential, which couples two lithographically defined waveguides and reverses the condensate's propagation direction. By varying the structural sizes, we utilize the conjunction of the different dimensionalities to additionally evidence the functionality of a polaritonic resonant tunnel diode. Furthermore, we investigate the ultra fast dynamics of the device via ps-resolved streak camera measurements, which is distinctive for the polariton platform. This scalable, all-directional coupler element is a central building block for compact non-linear on-chip photonic architectures.

cond-mat.mes-hall↗

arXiv2018

Evolution of temporal coherence in confined polariton condensates

We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor microcavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasi-condensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set. By increasing the pump power beyond the condensation threshold, temporal coherence significantly improves in devices with increased spatial confinement, as revealed in the transition from thermal to coherent statistics of the emitted light.

cond-mat.quant-gas↗

arXiv2018

Photon number-resolved measurement of an exciton-polariton condensate

We measure the full photon-number distribution emitted from a Bose condensate of microcavity exciton-polaritons confined in a micropillar cavity. The statistics are acquired by means of a photonnumber resolving transition edge sensor. We directly observe that the photon-number distribution evolves with the non-resonant optical excitation power from geometric to quasi-Poissonian statistics, which is canonical for a transition from a thermal to a coherent state. Moreover, the photon-number distribution allows evaluating the higher-order photon correlations, shedding further light on the coherence formation and phase transition of the polariton condensate. The experimental data is analyzed in terms of thermal coherent states which allows one to directly extract the thermal and coherent fraction from the measured distributions. These results pave the way for a full understanding of the contribution of interactions in light-matter condensates in the coherence buildup at threshold.

cond-mat.mes-hall↗

arXiv2018

Single photons and unconventional photon blockade in quantum dot cavity-QED

We observe the unconventional photon blockade effect in quantum dot cavity QED, which, in contrast to conventional photon blockade, operates in the weak coupling regime. A single quantum dot transition is simultaneously coupled to two orthogonally polarized optical cavity modes, and by careful tuning of the input and output state of polarization, the unconventional photon blockade effect is observed. We find a minimum second-order correlation $g^{(2)}(0)\approx0.37$ which corresponds to $g^{(2)}(0)\approx0.005$ when corrected for detector jitter, and observe the expected polarization dependency and photon bunching and anti-bunching very close-by in parameter space, which indicates the abrupt change from phase to amplitude squeezing.

quant-ph↗

arXiv2017

The Unconventional Photon Blockade

We review the unconventional photon blockade mechanism. This quantum effect remarkably enables a strongly sub-Poissonian light statistics, even from a system characterized by a weak single photon nonlinearity. We revisit the past results, which can be interpreted in terms of quantum interferences or optimal squeezing, and show how recent developments on input-output field mixing can overcome the limitations of the original schemes towards passive and integrable single photon sources. We finally present some valuable alternative schemes for which the unconventional blockade can be directly adapted.

quant-ph↗

arXiv2017

Kinetic Monte Carlo Approach to Non-equilibrium Bosonic Systems

We consider the use of a Kinetic Monte Carlo approach for the description of non-equilibrium bosonic systems, taking non-resonantly excited exciton-polariton condensates and bosonic cascade lasers as examples. In the former case, the considered approach allows the study of the cross-over between incoherent and coherent regimes, which represents the formation of a quasi-condensate that forms purely from the action of energy relaxation processes rather than interactions between the condensing particles themselves. In the latter case, we show that a bosonic cascade can theoretically develop an output coherent state.

cond-mat.mes-hall↗

arXiv2017

Multivalley engineering in semiconductor microcavities

We consider exciton-photon coupling in semiconductor microcavities in which separate periodic potentials have been embedded for excitons and photons. We show theoretically that this system supports degenerate ground-states appearing at non-zero in-plane momenta, corresponding to multiple valleys in reciprocal space, which are further separated in polarization corresponding to a polarization-valley coupling in the system. Aside forming a basis for valleytronics, the multivalley dispersion is predicted to allow for spontaneous momentum symmetry breaking and two-mode squeezing under non-resonant and resonant excitation, respectively.

cond-mat.mes-hall↗

arXiv2017

Exciton-Polariton Flows in Cross-Dimensional Junctions

We study the nonequilibrium exciton-polariton condensation in 1D to 0D and 1D to 2D junctions by means of non-resonant spectroscopy. The shape of our potential landscape allows to probe the resonant transmission of a propagating condensate between a quasi-1D waveguide and cylindrically symmetric states. We observe a distinct mode selection by varying the position of the non-resonant pump laser. Moreover, we study the the case of propagation from a localized trapped condensate state into a waveguide channel. Here, the choice of the position of the injection laser allows us to tune the output in the waveguide. Our measurements are supported by an accurate Ginzburg-Landau modeling of the system shining light on the underlying mechanisms.

cond-mat.mes-hall↗

arXiv2017

Nonclassical statistics from a polaritonic Josephson junction

We theoretically study the emission statistics of a weakly nonlinear photonic dimer during coherent oscillations. We show that the phase and population dynamics allow to periodically meet an optimal intensity squeezing condition resulting in a strongly nonclassical emission statistics. By considering an exciton-polariton Josephson junction resonantly driven by a classical source, we show that a sizeable antibunching should emerge in such semiconductor system where intrinsic nonclassical signatures have remained elusive to date.

cond-mat.mes-hall↗

arXiv2016

Single photons from dissipation in coupled cavities

We propose a single photon source based on a pair of weakly nonlinear optical cavities subject to a one-directional dissipative coupling. When both cavities are driven by mutually coherent fields, sub-poissonian light is generated in the target cavity even when the nonlinear energy per photon is much smaller than the dissipation rate. The sub-poissonian character of the field holds over a delay measured by the inverse photon lifetime, as in the conventional photon blockade, thus allowing single-photon emission under pulsed excitation. We discuss a possible implementation of the dissipative coupling relevant to photonic platforms.

quant-ph↗

arXiv2016

Bright solitons in non-equilibrium coherent quantum matter

We theoretically demonstrate a mechanism for bright soliton generation in spinor non-equilibrium Bose-Einstein condensates made of atoms or quasiparticles such as polaritons in semiconductor microcavities. We give analytical expressions for bright (half) solitons as minimizing functions of a generalized non-conservative Lagrangian elucidating the unique features of inter and intra-competition in non-equilibrium systems. The analytical results are supported by a detailed numerical analysis that further shows the rich soliton dynamics inferred by their instability and mutual cross-interactions.

nlin.PS↗

arXiv2015

Dissipative soliton protocols in semiconductor microcavities at finite temperatures

We consider exciton polaritons in a semiconductor microcavity with a saturable absorber in the growth direction of the heterostructure. This feature promotes additional nonlinear losses of the system with the emergence of bistability of the condensate particles number on the nonresonant (electrical or optical) excitation intensity. Further we demonstrate a new type of bright spatial dissipative exciton-polariton soliton which emerges in the equilibrium between the regions with different particle density. We develop protocols of soliton creation and destruction. The switch to a soliton-like behavior occurs if the cavity is exposed by a short strong laser pulse with certain energy and duration. We estimate the characteristic times of soliton switch on and off and the time of return to the initial cycle. In particular, we demonstrate surprising narrowing of the spatial profile of the soliton and its vanishing at certain temperature due to interaction of the system with the thermal bath of acoustic phonons. We also address the role of polariton-polariton interaction (Kerr-like nonlinearity) on formation of dissipative solitons and show that the soliton may exist both in its presence and absence.

cond-mat.mes-hall↗

arXiv2015

Remote Macroscopic Entanglement on a Photonic Crystal Architecture

The outstanding progress in nanostructure fabrication and cooling technologies allows what was unthinkable a few decades ago: bringing single-mode mechanical vibrations to the quantum regime. The coupling between photon and phonon excitations is a natural source of nonclassical states of light and mechanical vibrations, and its study within the field of cavity optomechanics is developing lightning-fast. Photonic crystal cavities are highly integrable architectures that have demonstrated the strongest optomechanical coupling to date, and should therefore play a central role for such hybrid quantum state engineering. In this context, we propose a realistic heralding protocol for the on-chip preparation of remotely entangled mechanical states, relying on the state-of-the-art optomechanical parameters of a silicon-based nanobeam structure. Pulsed sideband excitation of a Stokes process, combined with single photon detection, allows writing a delocalised mechanical Bell state in the system, signatures of which can then be read out in the optical field. A measure of entanglement in this protocol is provided by the visibility of a characteristic quantum interference pattern in the emitted light.

quant-ph↗

arXiv2015

Quantum Treatment for Bose-Einstein Condensation in Non-Equilibrium Systems

We develop an approach based on stochastic quantum trajectories for an incoherently pumped system of interacting bosons relaxing their energy in a thermal reservoir. Our approach enables the study of the versatile coherence properties of the system. We apply the model to exciton polaritons in a semiconductor microcavity. Our results demonstrate the onset of macroscopic occupation in the lowest-energy mode accompanied by the establishment of both temporal and spatial coherence. We show that temporal coherence exhibits a transition from a thermal to coherent statistics and the spatial coherence reveals off-diagonal long-range order.

cond-mat.quant-gas↗

arXiv2015

An all-silicon single-photon source by unconventional photon blockade

The lack of suitable quantum emitters in silicon and silicon-based materials has prevented the realization of room temperature, compact, stable, and integrated sources of single photons in a scalable on-chip architecture, so far. Current approaches rely on exploiting the enhanced optical nonlinearity of silicon through light confinement or slow-light propagation, and are based on parametric processes that typically require substantial input energy and spatial footprint to reach a reasonable output yield. Here we propose an alternative all-silicon device that employs a different paradigm, namely the interplay between quantum interference and the third-order intrinsic nonlinearity in a system of two coupled optical cavities. This unconventional photon blockade allows to produce antibunched radiation at extremely low input powers. We demonstrate a reliable protocol to operate this mechanism under pulsed optical excitation, as required for device applications, thus implementing a true single-photon source. We finally propose a state-of-art implementation in a standard silicon-based photonic crystal integrated circuit that outperforms existing parametric devices either in input power or footprint area.

quant-ph↗

arXiv2014

Heralded Preparation and Readout of Entangled Phonons in a Photonic Crystal Cavity

We propose a realistic protocol for the preparation and readout of mechanical Bell states in an optomechanical system. The proposal relies on parameters characterizing a photonic crystal cavity mode, coupled to two localized flexural modes of the structure, but equally applies to other optomechanical systems in the same parameter range. The nonclassical states are heralded via optical postselection and revealed in specific interference patterns characterizing the emission at the cavity frequency.

quant-ph↗

arXiv2014

Non-Abelian Gauge Fields in Photonic Cavities and Photonic Superfluids

We show that the interplay between the structure anisotropy and the energy splitting between the TE and TM modes of a microcavity leads to the appearance of a gauge field for a propagating polariton condensate. This field is analog with a spin-orbit coupling and the field texture can be tuned by rotating the sample and ranges continuously from a Rashba to a monopolar field. In the linear regime, the monopolar field leads to a remarkable focusing effect. In the interacting regime, the effective spin-orbit coupling induces a breakdown of superfluidity. The spatially homogeneous flows become unstable and dynamically evolve into textured ground states such as stripes and domain walls.

cond-mat.quant-gas↗

arXiv2013

An exciton-polariton mediated all-optical router

We propose an all-optical nonlinear router based on a double barrier gate connected to periodically modulated guides. A semiconductor microcavity is driven nonresonantly in-between the barriers to form an exciton-polariton condensate on a discrete state that is subject to the exciton blueshift. The subsequent coherent optical signal is allowed to propagate through a guide provided that the condensate energy is resonant with a miniband or is blocked if it faces a gap. While a symmetric sample operates as an optical switch, its asymmetric counterpart embodies a router turned to be polarization selective under applied magnetic field.

cond-mat.mes-hall↗