Polariton Vortices Research Articles

ExSitu Production and Storage of Exciton-Polariton Vortices in Higher-Order Topological Corner Modes.

We propose a scheme for producing and manipulating quantized exciton-polariton vortices in the higher-order topological corner modes of a two-dimensional array of micropillars. By nonresonantly exciting p-orbital condensates with different orientations at two input corners, polariton vortices carrying the required topological charges can be controllably created at output corners away from the pumping spots. Besides, polariton vortices formed at input corners can be copied to the output corners through the topological edge states. Our scheme provides topological double insurance for intrinsic binary information memory and holds potential applications in remote information processing.

Plasmonic vortices host magnetoelectric interactions

The vector E×H and pseudoscalar E·H products of electric and magnetic fields are separately finite in vacuum transverse electric and magnetic (TEM) plane waves, and angular momentum structured light. Current theories of interactions beyond the standard model of particle physics invoke E·H≠0 as the source term in the axion law that describes interactions with the cosmological dark matter axion particles outside of the quartet of Maxwell's equations. E·H≠0 also drives relativistic spin-charge magnetoelectric excitations of axion quasiparticles at a distinctively higher condensed matter scale in magnetic and topological materials. Yet, how to drive coherent E·H response is unknown, and provides motivation to examine the field polarizations in structured light on a deep subdiffraction limited spatial scale and suboptical cycle temporal scale by ultrafast nonlinear photoemission electron microscopy. By analytical theory and ultrafast coherent photoemission electron microscopy, we image E·H fields in surface plasmon polariton vortex cores at subwavelength scales, where we find that the magnetoelectric relative to the dipole density is intensified on an ∼10-nm-diameter scale as a universal property of plasmonic vortex fields. The generation and nanoscale localization of E·H fields introduces the magnetoelectric symmetry class, having the parity P and time reversal T broken, but the joint PT symmetry preserved. The ability to image the optical fields of plasmonic vortex cores opens the research of ultrafast microscopy of magnetoelectric responses and interactions with axion quasiparticles in solid state materials. Published by the American Physical Society 2024

Electrically Controlling Vortices in a Neutral Exciton-Polariton Condensate at Room Temperature.

Manipulating bosonic condensates with electric fields is very challenging as the electric fields do not directly interact with the neutral particles of the condensate. Here we demonstrate a simple electric method to tune the vorticity of exciton-polariton condensates in a strong coupling liquid crystal (LC) microcavity with CsPbBr_{3} microplates as active material at room temperature. In such a microcavity, the LC molecular director can be electrically modulated giving control over the polariton condensation in different modes. For isotropic nonresonant optical pumping we demonstrate the spontaneous formation of vortices with topological charges of +1, +2, -2, and -1. The topological vortex charge is controlled by a voltage in the range of 1 to 10V applied to the microcavity sample. This control is achieved by the interplay of a built-in potential gradient, the anisotropy of the optically active perovskite microplates, and the electrically controllable LC molecular director in our system with intentionally broken rotational symmetry. Besides the fundamental interest in the achieved electric polariton vortex control at room temperature, our work paves the way to micron-sized emitters with electric control over the emitted light's phase profile and quantized orbital angular momentum for information processing and integration into photonic circuits.

Polariton vortex Chern insulator [Invited

We propose a vortex Chern insulator, motivated by recent experimental demonstrations on programmable arrangements of cavity polariton vortices by [S. Alyatkin et al., arXiv, ArXiv:2207.01850 (2022)10.48550/arXiv.2207.01850 ] and [J. Wang et al, Natl. Sci. Rev. 10, Nwac096 (2022)10.1093/nsr/nwac096]. In the absence of any external fields, time-reversal symmetry is spontaneously broken through polariton condensation into structured arrangements of localized co-rotating vortices. We characterize the response of the rotating condensate lattice by calculating the spectrum of Bogoliubov elementary excitations and observe the crossing of edge-states, of opposite vorticity, connecting bands with opposite Chern numbers. The emergent topologically nontrivial energy gap stems from inherent vortex anisotropic polariton-polariton interactions and does not require any spin-orbit coupling, external magnetic fields, or elliptically polarized pump fields.

Spin-orbit-locked hyperbolic polariton vortices carrying reconfigurable topological charges

The topological features of optical vortices have been opening opportunities for free-space and on-chip photonic technologies, e.g., for multiplexed optical communications and robust information transport. In a parallel but disjoint effort, polar anisotropic van der Waals nanomaterials supporting hyperbolic phonon polaritons (HP2s) have been leveraged to drastically boost light-matter interactions. So far HP2 studies have been mainly focusing on the control of their amplitude and scale features. Here we report the generation and observation of mid-infrared hyperbolic polariton vortices (HP2Vs) associated with reconfigurable topological charges. Spiral-shaped gold disks coated with a flake of hexagonal boron nitride are exploited to tailor spin–orbit interactions and realise deeply subwavelength HP2Vs. The complex interplay between excitation spin, spiral geometry and HP2 dispersion enables robust reconfigurability of the associated topological charges. Our results reveal unique opportunities to extend the application of HP2s into topological photonics, quantum information processing by integrating these phenomena with single-photon emitters, robust on-chip optical applications, sensing and nanoparticle manipulation.

Ultrafast microscopy of a twisted plasmonic spin skyrmion

We report a transient plasmonic spin skyrmion topological quasiparticle within surface plasmon polariton vortices, which is described by analytical modeling and imaging of its formation by ultrafast interferometric time-resolved photoemission electron microscopy. Our model finds a twisted skyrmion spin texture on the vacuum side of a metal/vacuum interface and its integral opposite counterpart in the metal side. The skyrmion pair forming a hedgehog texture is associated with co-gyrating anti-parallel electric and magnetic fields, which form intense pseudoscalar E·B focus that breaks the local time-reversal symmetry and can drive magnetoelectric responses of interest to the axion physics. Through nonlinear two-photon photoemission, we record attosecond precision images of the plasmonic vectorial vortex field evolution with nanometer spatial and femtosecond temporal (nanofemto) resolution, from which we derive the twisted plasmonic spin skyrmion topological textures, their boundary, and topological charges; the modeling and experimental measurements establish a quantized integer photonic topological charge that is stable over the optical generation pulse envelope.

Polarization-controlled generation and superposition of surface plasmon polariton vortices with a plasmonic metasurface

Optical vortex that carries orbital angular momentum has shown great potential in various applications, including high-density optical communication, quantum information, and manipulation of small particles. Here, an approach to design a plasmonic metasurface that can control both the generation and superposition of surface plasmon polariton (SPP) vortices is proposed and demonstrated. Under circularly polarized light incidence, the SPP vortices with different topological charges can be generated depending on the spin of the incidence, and the superposition state can be achieved when the polarization of incident light turns to linear polarization. Furthermore, it is demonstrated that the superposition of SPP vortices can be accurately controlled by the polarization states of the incidence. This proposed approach is quite versatile for generating and controlling SPP vortices and provides a feasible way to design miniaturized photonic devices for on-chip optical micromanipulation, sensing, and other related applications.

Formation dynamics of exciton-polariton vortices created by nonresonant annular pumping

We study the spontaneous formation of exciton polariton vortices in an all-optical non-resonantly excited annular trap, which is formed by ring-shaped subpicosecond laser pulses. Since the light emitted by these vortices carries orbital angular momentum (OAM) corresponding to their topological charge, we apply a dedicated OAM spectroscopy technique to detect the OAM of the measurement signal with picosecond time resolution. This allows us to identify the formation of OAM modes and investigate the dynamics of the vortex formation process. We also study the power dependence of this process and how the ring diameter influences the formation of OAM modes.

Realization of all-optical vortex switching in exciton-polariton condensates

Vortices are topological objects representing the circular motion of a fluid. With their additional degree of freedom, the vorticity, they have been widely investigated in many physical systems and different materials for fundamental interest and for applications in data storage and information processing. Vortices have also been observed in non-equilibrium exciton-polariton condensates in planar semiconductor microcavities. There they appear spontaneously or can be created and pinned in space using ring-shaped optical excitation profiles. However, using the vortex state for information processing not only requires creation of a vortex but also efficient control over the vortex after its creation. Here we demonstrate a simple approach to control and switch a localized polariton vortex between opposite states. In our scheme, both the optical control of vorticity and its detection through the orbital angular momentum of the emitted light are implemented in a robust and practical manner.

Interaction of an Archimedean spiral structure with orbital angular momentum light

Complementing the research of surface plasmon polariton vortices for Archimedean spiral structures grooved in gold platelets, we here study the analogous positive structure of an Archimedean spiral consisting of bent gold nanorods. We consider spirals of two different sizes, for which we perform numerical calculations with the boundary element method. For a micrometer-sized metallic structure we show that the scattered electric field forms a vortex in the centre of the spiral. When the spiral is illuminated by orbital angular momentum light, the topological charge of the vortex can be controlled. For a nanometer-sized plasmonic Archimedean spiral we find that the response to optical excitation is governed by several resonances. When the nanostructure is excited by orbital angular momentum light, different resonances appear compared to the excitation with plane waves. Our results highlight that the distinct architecture of the Archimedean spiral responds in a unique way to the excitation with orbital angular momentum light.

Generation of optical vortices by exciton polaritons in pillar semiconductor microcavities.

We propose a scheme to generate optical vortices through exciting exciton polariton vortices by a Gaussian beam in a pillar microcavity. With coupled Gross-Piteavskii equations we find that the structure of the exciton polariton vortices and antivortices shows a strong dependence on the microcavity radius, pump geometry, and nonlinear exciton-exciton interaction. Due to the nonlinear exciton-exciton interaction the strong Gaussian beam cannot excite more exciton polariton vortices or antivortices with respect to the weak one. The calculation demonstrates that the weak Gaussian beam can excite vortex-antivortex pairs, vortices with high total orbital angular momentum, and superposition states of vortex and antivortex with high total opposite orbital angular momentum. The pump geometry for the Gaussian beam to excite these vortex structures is analyzed in detail, which shows a potential application for generating optical vortex beams.

Cnoidal waves, solitons and vortices in the flow of polaritons

We theoretically have investigated the properties of the phonon-polariton waves propagating in Kerr-type dielectric medium, and examined the conditions of appearance of the spatial solitons, cnoidal waves and polariton vortices. It is shown that the polariton flow can propagate in the form of spatial soliton, or can be split into several flows in the form of filaments depending on the field density and parameters of the nonlinear medium. In the polariton flow the vortices may appear at the presence of local inhomogeneities of medium refractive index causing the wavefront rotation.

Vortex lattice of surface plasmon polaritons

We theoretically investigate the formation of a plasmon polariton vortex lattice on a metal surface following the interference of surface plasmon polaritons (SPPs). The plasmon polariton vortex lattice is formed by the interference of the SPP transverse-magnetic mode (TM-mode) and electric mode (E-mode) in the presence of the inhomogeneity with a curvilinear boundary on the surface of the metal layer. The SPP vortex lattice can be controlled by changing the configuration of the boundary. Weak nonlinearity of the metal permittivity does not change the interference pattern, but it increases the propagation length of the SPPs and, therefore, the area of the vortex lattice too.

Cogwheels for generation of surface plasmon polariton vortex

We propose a cogwheel structure formed by an air ring and equally distributed air cogs along the ring on a gold film for generation of surface plasmon polariton vortex. We show that a well-designed cogwheel can generate an optical vortex-like response and that the characteristics of such SPP vortex are directly related to cogwheel geometries and can be controlled by adjusting the polarisation direction of incident light.

Hydrodynamic nucleation of quantized vortex pairs in a polariton quantum fluid

Quantized vortices appear in quantum gases at the breakdown of superfluidity. In liquid helium and cold atomic gases, they have been indentified as the quantum counterpart of turbulence in classical fluids. In the solid state, composite light‐matter bosons known as exciton polaritons have enabled studies of non-equilibrium quantum gases and superfluidity. However, there has been no experimental evidence of hydrodynamic nucleation of polariton vortices so far. Here we report the experimental study of a polariton fluid flowing past an obstacle and the observation of nucleation of quantized vortex pairs in the wake of the obstacle. We image the nucleation mechanism and track the motion of the vortices along the flow. The nucleation conditions are established in terms of local fluid density and velocity measured on the obstacle perimeter. The experimental results are successfully reproduced by numerical simulations based on the resolution of the Gross‐Pitaevskii equation. H ydrodynamic instabilities in classical fluids were studied in the pioneering experiments of BOnard in the 1910’s. Convective BOnardRayleigh flows and BOnardVon KAErmAEn streets are now well known examples in nonlinear and chaos sciences 1 . In conventional fluids, the flow around an obstacle is characterized by the dimensionless Reynolds number ReD vR= , withv and the fluid velocity and dynamical viscosity, respectively, and R the diameter of the obstacle. When increasing the Reynolds number, laminar flow, stationary vortices, BOnardVon KAErmAEn streets of moving vortices and fully turbulent regimes are successively observed in the wake of the obstacle 1 .

Selective photoexcitation of confined exciton-polariton vortices

We resonantly excite exciton-polariton states confined in cylindrical traps. Using a homodyne detection setup, we are able to image the phase and amplitude of the confined polariton states. We evidence the excitation of vortex states, carrying an integer angular orbital momentum $m$, analogous to the transverse $TE{M}_{{01}^{\ensuremath{\ast}}}$ ``donut'' mode of cylindrically symmetric optical resonators. Tuning the excitation conditions allows us to select the charge of the vortex. In this way, the injection of singly charged $(m=1\text{ }\text{and}\text{ }m=\ensuremath{-}1)$ and doubly charged $(m=2)$ polariton vortices is shown. This work demonstrates the potential of in-plane confinement coupled with selective excitation for the topological tailoring of polariton wave functions.

Phase-resolved imaging of confined exciton-polariton wave functions in elliptical traps

We study the wave functions of exciton polaritons trapped in the elliptical traps of a patterned microcavity. A homodyne detection setup with numerical off-axis filtering allows us to retrieve the amplitude and the phase of the wave functions. Doublet states are observed as the result of the ellipticity of the confinement potential and are successfully compared to even and odd solutions of Mathieu equations. We also show how superpositions of odd and even states can be used to produce ``donut'' and ``eight-shape'' states which can be interpreted as polariton vortices.

Excitation of vortices in semiconductor microcavities

We predict that the transverse electric-magnetic polarization splitting of exciton polaritons allows a simple technique for the generation of polariton vortices of winding number 2 in semiconductor microcavities. The vortices can be excited by circularly polarized light having no orbital angular momentum and observed as phase vortices in the opposite circular polarization or directly as linear polarization vortices. The prediction is explained by a simplified analytical linear model and shown fully with a numerical model based on the Gross-Pitaevskii equations, which includes the nonlinear effects of polariton-polariton interactions.