Phase Of Polaritons Research Articles

Second-Order Temporal Coherence of Polariton Lasers Based on an Atomically Thin Crystal in a Microcavity.

Bosonic condensation and lasing of exciton polaritons in microcavities is a fascinating solid-state phenomenon. It provides a versatile platform to study out-of-equilibrium many-body physics and has recently appeared at the forefront of quantum technologies. Here, we study the photon statistics via the second-order temporal correlation function of polariton lasing emerging from an optical microcavity with an embedded atomically thin MoSe_{2} crystal. Furthermore, we investigate the macroscopic polariton phase transition for varying excitation powers and temperatures. The lower-polariton exhibits photon bunching below the threshold, implying a dominant thermal distribution of the emission, while above the threshold, the second-order correlation transits towards unity, which evidences the formation of a coherent state. Our findings are in agreement with a microscopic numerical model, which explicitly includes scattering with phonons on the quantum level.

Coherent Microwave Emission of Gain-Driven Polaritons

By developing a gain-embedded cavity magnonics platform, we create a gain-driven polariton (GDP) that is activated by an amplified electromagnetic field. Distinct effects of gain-driven light-matter interaction, such as polariton auto-oscillations, polariton phase singularity, self-selection of a polariton bright mode, and gain-induced magnon-photon synchronization, are theoretically studied and experimentally manifested. Utilizing the gain-sustained photon coherence of the GDP, we demonstrate polariton-based coherent microwave amplification (∼40 dB) and achieve high-quality coherent microwave emission (Q>10^{9}).

Topological Frenkel exciton polaritons in one-dimensional lattices of strongly coupled cavities

Frenkel polaritons, hybrid light-matter quasiparticles, offer promise for the designing of new optoelectronic devices. However, their technological implementations are hindered by sensitivity to imperfections. Topology has been raised as a way to circumvent defects and fabrication limitations. Here, we propose a lattice of cavities to realize the one-dimensional Su-Schrieffer-Heeger model (SSH) for topological Frenkel polaritons. By engineering the configuration of the cavities we demonstrate that the SSH topological and trivial phases can be accessed, which we unravel by employing a dual approach based on classical and quantum theories. We study the role of inherent vibron modes and fabrication defects in the robustness of the topological phases of polaritons. Our study demonstrates a simple experimentally realistic setup to realize topological polaritons at room temperature.

Topological Phases of Polaritons in a Cavity Waveguide.

We study the unconventional topological phases of polaritons inside a cavity waveguide, demonstrating how strong light-matter coupling leads to a breakdown of the bulk-edge correspondence. We observe an ostensibly topologically nontrivial phase, which unexpectedly does not exhibit edge states. Our findings are in direct contrast to topological tight-binding models with electrons, such as the celebrated Su-Schrieffer-Heeger (SSH) model. We present a theory of collective polaritonic excitations in a dimerized chain of oscillating dipoles embedded inside a photonic cavity. The added degree of freedom from the cavity photons upgrades the system from a typical SSH SU(2) model into a largely unexplored SU(3) model. Tuning the light-matter coupling strength by changing the cavity size reveals three critical points in parameter space: when the polariton band gap closes, when the Zak phase changes from being trivial to nontrivial, and when the edge state is lost. These three critical points do not coincide, and thus the Zak phase is no longer an indicator of the presence of edge states. Our discoveries demonstrate some remarkable properties of topological matter when strongly coupled to light, and could be important for the growing field of topological nanophotonics.

Polariton Anomalous Hall Effect in Transition-Metal Dichalcogenides.

We analyze the properties of strongly coupled excitons and photons in systems made of semiconducting two-dimensional transition-metal dichalcogenides embedded in optical cavities. Through a detailed microscopic analysis of the coupling, we unveil novel, highly tunable features of the spectrum that result in polariton splitting and a breaking of light-matter selection rules. The dynamics of the composite polaritons is influenced by the Berry phase arising both from their constituents and from the confinement-enhanced coupling. We find that light-matter coupling emerges as a mechanism that enhances the Berry phase of polaritons well beyond that of its elementary constituents, paving the way to achieve a polariton anomalous Hall effect.

Controlled steering of Cherenkov surface plasmon wakes with a one-dimensional metamaterial.

In the Cherenkov effect a charged particle moving with a velocity faster than the phase velocity of light in the medium radiates light that forms a cone with a half angle determined by the ratio of the two speeds. Here, we show that by creating a running wave of polarization along a one-dimensional metallic nanostructure consisting of subwavelength-spaced rotated apertures that propagates faster than the surface plasmon polariton phase velocity, we can generate surface plasmon wakes, a two-dimensional analogue of Cherenkov radiation. The running wave of polarization travels with a speed determined by the angle of incidence and the photon spin angular momentum of the incident radiation. By changing either one of these properties we demonstrate controlled steering of the Cherenkov surface plasmon wakes.

Spin canting induced nonreciprocal Goos-Hänchen shifts.

Recent studies on surface reflection illustrate how light beams can be laterally shifted from the position predicted by geometrical optics, the so called Goos-Hänchen effect. In antiferromagnets this shifts can be controlled with an external magnetic field. We show that a configuration in which spins cant in response to applied magnetic fields enhance possibilities of field controlled shifts. Moreover, we show that nonreciprocal displacements are possible, for both oblique and normal incidence, due to inherent nonreciprocity of the polariton phase with respect to the propagation direction. In the absence of an external field, reciprocal displacements occur.

Ginzburg-Landau theory for the Jaynes-Cummings-Hubbard model

We develop a Ginzburg-Landau theory for the Jaynes-Cummings-Hubbard model which effectively describes both static and dynamic properties of photons evolving in a cubic lattice of cavities, each filled with a two-level atom. To this end we calculate the effective action to first-order in the hopping parameter. Within a Landau description of a spatially and temporally constant order parameter we calculate the finite-temperature mean-field quantum phase boundary between a Mott insulating and a superfluid phase of polaritons. Furthermore, within the Ginzburg-Landau description of a spatio-temporal varying order parameter we determine the excitation spectra in both phases and, in particular, the sound velocity of light in the superfluid phase.

Soliton Instabilities and Vortex Street Formation in a Polariton Quantum Fluid

Excitonpolaritons have been shown to be an optimal system in order to investigate the properties of bosonic quantum fluids. We report here on the observation of dark solitons in the wake of engineered circular obstacles and their decay into streets of quantized vortices. Our experiments provide a time-resolved access to the polariton phase and density, which allows for a quantitative study of instabilities of freely evolving polaritons. The decay of solitons is quantified and identified as an effect of disorder-induced transverse perturbations in the dissipative polariton gas.

Study of surface plasmon polaritons near the photonic‐bandgap edge for interphotonic band switching devices

The photonic energy band structures near the bandgap edges of surface plasmon polariton in dielectric lattice structures on a smooth silver film were studied. At the bandgap edges, sharp changes of the surface plasmon polariton's transmittance arise owing to small changes in the refractive index around the lattice structure, which results in the band transition between the pass band and the stop band. On the analogy of 'the phase transition' between the surface plasmon polariton's conductive phase and the insulation phase, the surface plasmon polariton's phase diagram of the 1D lattice structure at a single frequency (lambda approximately 780 nm) with parameters of the pitch and the refractive index of lattice were investigated. At the boundary, the most sensitive transition was found between the second pass band and the first stop band, with the approximately 0.5 lattice filling factor. The surface plasmon polariton's phase state has been determined by far-field observation using an optical microscope.

Mott-Insulating and Glassy Phases of Polaritons in 1D Arrays of Coupled Cavities

By means of analytical and numerical methods we analyze the phase diagram of polaritons in one-dimensional coupled cavities. We locate the phase boundary, discuss the behavior of the polariton compressibility and visibility fringes across the critical point, and find a nontrivial scaling of the phase boundary as a function of the number of atoms inside each cavity. We also predict the emergence of a polaritonic glassy phase when the number of atoms fluctuates from cavity to cavity.

Interaction between a high-density polariton phase and the exciton environment in semiconductor microcavities

Spontaneous polariton coherence is observed following creation of a cool exciton distribution in a GaAs-based semiconductor microcavity. Interactions between the high density polariton state and high-$k$ excitons result in a blueshift in energy and are shown to limit the temporal coherence of the polariton phase to $10--20\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$. The effect of exciton-polariton interaction is also revealed in two beam experiments where the coherence of the polariton optical parametric oscillator is strongly suppressed by the creation of a reservoir population. These interactions are likely to be important in any polariton high density phase created under conditions of nonresonant excitation.

Room-temperature polariton lasers based on GaN microcavities

The critical temperature for Bose condensation of exciton polaritons in an AlGaN microcavity containing 9 GaN quantum wells is calculated to be T=460 K. We have modeled the kinetics of polaritons in such a microcavity device using the two-dimensional Boltzmann equation. Room-temperature lasing is found with a threshold as small as 100 mW. The kinetic blocking of polariton relaxation that prevents formation of the Bose-condensed phase of polaritons at low temperatures disappears at high temperatures, especially in n-doped samples. Thus, GaN microcavities are excellent candidates for realization of room-temperature polariton lasers.

Four-wave scattering of light by coherently excited polaritons

An analysis was made of four-wave scattering of light by coherently excited phonon polaritons in homogeneous LiIO3 and Mg:LiNbO3 crystals, and also in periodically poled Nd:Mg:LiNbO3. An investigation of lithium niobate crystals revealed a considerable discrepancy between the theoretically predicted and the experimentally determined dependences of the Stokes component intensity on the polariton phase mismatch. General expressions were derived for the line profile of the four-wave scattering in crystals with a periodic distribution of their nonlinear optical properties and in spatially confined nonlinear regions.

Generalized polariton phase matching in enhanced Raman scattering

Generalized polariton phase matching in enhanced Raman scattering