Polariton Field Research Articles

Unveiling the Loss Mode Enabled Tunable Plasmonic Chirality at Flat Metal Surface.

Plasmonic chirality has garnered significant interest in the past decade due to its enhanced chiral light-matter interactions. Current methods for achieving plasmonic chirality often rely on complex nanostructures or metamaterials, which are hampered by intricate fabrication processes. In this work, we present an approach to generate plasmonic chiral structured surface plasmon polariton (s-SPP) fields on a single, flat metal surface, bypassing elaborate fabrication techniques. The plasmonic chiral s-SPP fields are excited by the superposition of multiple differently oriented transverse magnetic polarized plane waves. We demonstrate, both theoretically and experimentally, the flexible tuning of chiral plasmonic patterns by adjusting the symmetry and phase differences of the incident waves. This method provides a facile mean to optically tailor plasmonic chiral properties on a subwavelength scale, offering potential applications in sensing, enantioselective reactions, imaging, and reconfigurable chiral switches.

Simulation Study of Dynamic Rotation and Deformation for Plasmonic Electric Field-Skyrmions

The topological properties of optical skyrmions in confined electromagnetic fields are perfectly presented through spin vectors and electric-field vectors. However, currently, electric-field optical skyrmions in surface plasmon polaritons are mostly presented in the form of a Néel type. Most control strategies involve linear directional movement, and topological manipulation methods are monotonous. We specifically propose a multi-arc symmetric slit array, which generates skyrmions from the surface plasmon polariton (SPP) field under excitation of a linearly polarized Gaussian light-source array and exhibits strong dependence processes on the rotation, deformation, and phase distribution of the incident light source. We also discuss the independence and synthesis of deformation and rotation related to phase difference and positions of regulation, respectively, which provide the possibility for rich deformations under different rotation states. Our work extends new ideas for the dynamic control of plasmonic skyrmions, which is of great significance to fields such as spin photonics and nano-positioning.

Long-range molecular energy transfer mediated by strong coupling to plasmonic topological edge states

Abstract Strong coupling between light and molecular matter is currently attracting interest both in chemistry and physics, in the fast-growing field of molecular polaritonics. The large near-field enhancement of the electric field of plasmonic surfaces and their high tunability make arrays of metallic nanoparticles an interesting platform to achieve and control strong coupling. Two dimensional plasmonic arrays with several nanoparticles per unit cell and crystalline symmetries can host topological edge and corner states. Here we explore the coupling of molecular materials to these edge states using a coupled-dipole framework including long-range interactions. We study both the weak and strong coupling regimes and demonstrate that coupling to topological edge states can be employed to enhance highly-directional long-range energy transfer between molecules.

Extracting kinetic information from short-time trajectories: relaxation and disorder of lossy cavity polaritons

Abstract The emerging field of molecular cavity polaritons has stimulated a surge of experimental and theoretical activities and presents a unique opportunity to develop the many-body simulation methodology. This paper presents a numerical scheme for the extraction of key kinetic information of lossy cavity polaritons based on the transfer tensor method (TTM). Steady state, relaxation timescales, and oscillatory phenomena can all be deduced directly from a set of transfer tensors without the need for long-time simulation. Moreover, we generalize TTM to disordered systems by sampling dynamical maps and achieve fast convergence to disordered-averaged dynamics using a small set of realizations. Together, these techniques provide a toolbox for characterizing the interplay of cavity loss, disorder, and cooperativity in polariton relaxation and allow us to predict unusual dependences on the initial excitation state, photon decay rate, strength of disorder, and the type of cavity models. Thus, using the example of cavity polaritons, we have demonstrated significant potential in the use of the TTM toward both the efficient computation of long-time polariton dynamics and the extraction of crucial kinetic information about polariton relaxation from a small set of short-time trajectories.

Whispering-Gallery Quantum-Well Exciton Polaritons in an Indium Gallium Arsenide Microdisk Cavity.

Despite appealing high-symmetry properties that enable strong spatial confinement and ultrahigh-Q, optical whispering-gallery modes of spherical and circular resonators have been absent from the field of quantum-well exciton polaritons. Here we observe whispering-gallery exciton polaritons in a gallium arsenide microdisk cavity filled with indium gallium arsenide quantum wells, the test bed materials of polaritonics. Strong coupling is evidenced in photoluminescence and resonant spectroscopy accessed through concomitant confocal microscopy and near-field optical techniques. Excitonic and optical resonances are tuned by varying temperature and disk radius, revealing Rabi splittings between 5 and 10meV. A dedicated analytical quantum model for such circular whispering-gallery polaritons is developed, which reproduces the measured values. At high power, lasing is observed and accompanied by a blueshift of the emission consistent with the regime of polariton lasing. With experimental methods and theory now established, whispering-gallery-mode polaritons in round dielectric resonators appear as a new viable platform toward low loss polaritonics.

Polaritonics: introduction to feature issue

In the evolving landscape of modern science and technology, the field of polaritonics has emerged as a beacon of innovation and discovery. With its roots grounded in the coherent interplay of light and matter, polaritonics has pushed the boundaries of our understanding of many-body and quantum phenomena, and harnessed their potential for revolutionary applications. We are delighted to introduce this special issue, dedicated to exploring the cutting-edge of polaritonics research and its profound implications for various domains of science.

Modelling of asymmetric channel plasmonic polariton waveguides

Channel plasmonic polariton (CPP) waveguides are a promising technology for integrated photonics. They offer several advantages over other plasmonic waveguides and are well-suited for various applications. In this research, a new design of asymmetric double-trenched CPP waveguide is suggested and examined. This design consists of two silicon trenches etched into a silicon dioxide substrate layer; with a gold layer sandwiched in between. The trenches are asymmetric, with one trench being wider than the other. This asymmetry creates a spatially varying surface plasmon polariton (SPP) field, which can guide light along the waveguide. The polarization characteristics of this proposed design are analyzed over a specific wavelength range (0.7 - 1.7 µm) to evaluate the mode confinement of the light within the structure. The design performance was optimized by changing the gold layer thickness and the dimensions of the lower trench. Different scenarios are examined to observe TE and TM-polarized modes’ behavior within the groove. A 1867.119 dB/µm suppression level at 0.92 µm wavelength is achieved which offers a small-size component for compact photonic logic gates, enabling the development of next-generation photonic devices.

Manipulation of surface plasmon polariton fields excitation at quantum-size slit in a dielectric and graphene interface

The dispersion relation of surface plasmon polaritons is controlled and modified at the interface of atomic and Graphene medium. The beats patterns and moire fringes spacing are modified from vectorial character of the waves and parameters of the driving fields coupled with system energy levels. The beats patterns are investigated with the influence of control fields and its parameters. It is reported that the phase shifts Φ1,2 are the strong functions of the probe detuning and distance x along the interface. The light and surface plasmon polariton waves polarization is a strong oscillation function of both the position and time variation as well as driving fields parameters. The maximum value of phase sensitivity SΦ1 is 600 and SΦ2 is 400 radian per unit change of refractive index of the atomic medium at x=20λ. This work is particularly useful for surface plasmon resonance sensors technology.

Routes to chaos and generation of cnoidal wave envelopes in exciton-polariton microcavities

We show the presence of intermittent chaos as a function of the variation of the chemical potential during the condensation of exciton-polaritons using the bifurcation diagram and the Lyapunov Exponent. We then show the possibility of controlling the chaos in the homogeneous solution by the variation of the chemical potential when the pump increases. The influence of the chemical potential is demonstrated in stationary state by studying stability using the Routh-Hurwitz criterion. We also prove the existence of cnoidal waves and through phase portraits, their stabilities in propagation are established using the notion of symmetry. For this, we use a dissipative Gross-Pitaevskii equation for the polariton field, coupled to a reservoir dynamics equation, commonly used to describe polariton condensates under non-resonant pumping.

Symmetrical dual D-shape fiber for waveguide coupled surface plasmon resonance sensing

A waveguide-coupled surface plasmon resonance (WCSPR) sensor consisting of two D-shape single-mode fibers is designed and analyzed by the finite element method (FEM). The optical field of the surface plasmon polaritons (SPPs) mode is confined in the dielectric cavity between the dual metallic thin films. Therefore, the effective refractive index of the SPP mode depends largely on the refractive index of the analyte and an anomalous dispersion relationship is observed between the SPP mode and x-polarized core-guide mode of the dual D-shape fiber. The excitation mechanism of surface plasmon resonance (SPR) in the coupling region is attributed to phase matching of the two modes. Further analysis shows that the narrow bandwidth peak in the loss spectrum of the core mode is determined by the sensor dimensions contributed jointly by the thicknesses of the silver film, dielectric layer, and titanium dioxide film. Compared to the single-fiber structure, the optimized dual D-shape WCSPR sensor achieves a maximum wavelength sensitivity of 52,200 nm/RIU with a full-width at half-minimum (FWHM) of 9.47 nm and a figure of merit (FOM) of 346.6 RIU−1 in the analyte refractive index range of 1.32–1.42.

Polaromechanics: polaritonics meets optomechanics

Cavity exciton polariton physics and cavity optomechanics have evolved into mature and active domains with, so far, very little connections between them. We argue here that there are strong reasons to bridge the two fields, opening interesting opportunities. Polaritons are entities sharing the properties of photons and excitons in a controllable way. They can lead to tunable and strongly enhanced optomechanical couplings and, through them, to single-particle cooperativies C0 > 1 as well as ultra-strong optomechanical coupling in the many-particle regime. Besides, exciton-exciton Coulomb interactions define a new regime of non-linear many-body optomechanics with notable and largely unexplored consequences. Conversely, coherent vibrations can add a qualitatively distinct ingredient to the field of polaritonics by introducing the variable of time. Indeed, the mechanics built-in in polariton resonators allows for controllable time-modulation up to frequencies of tens of GHz with important consequences for the control of quantum emitters and bidirectional optical-to-microwave conversion. Most interestingly, it also enables polaritons to access Floquet physics, Landau-Zenner-Stückelberg state preparation, spinor pseudo-magnetic resonance, as well as optomechanically induced non-reciprocal phenomena. This guest-editorial addresses the opportunities and challenges in these emerging field.

Asynchronous locking in metamaterials of fluids of light and sound

Lattices of exciton-polariton condensates represent an attractive platform for the study and implementation of non-Hermitian bosonic quantum systems with strong non-linear interactions. The possibility to actuate on them with a time dependent drive could provide for example the means to induce resonant inter-level transitions, or to perform Floquet engineering or Landau-Zener-Stückelberg state preparation. Here, we introduce polaromechanical metamaterials, two-dimensional arrays of μm-sized traps confining zero-dimensional light-matter polariton fluids and GHz phonons. A strong exciton-mediated polariton-phonon interaction induces a time-dependent inter-site polariton coupling J(t) with remarkable consequences for the dynamics. When locally perturbed by continuous wave optical excitation, a mechanical self-oscillation sets-in and polaritons respond by locking the energy detuning between neighbor sites at integer multiples of the phonon energy, evidencing asynchronous locking involving the polariton and phonon fields. These results open the path for the coherent control of dissipative quantum light fluids with hypersound in a scalable platform.

The future of quantum in polariton systems: opinion

A significant amount of control of exciton-polaritons has been achieved over the past decades, including their creation, localization in desired modes, coupling between modes, manipulation by control fields, and detection. As quantum particles maintain coherence (correlations) for some time and interact (causing the evolution of those correlations), exciton-polaritons underlie an emerging field of quantum polaritonics.

Ghost Line Waves

Time-harmonic electromagnetic plane waves in anisotropic media can exhibit complex-valued wavevectors (with nonzero real and imaginary parts) even in the absence of material dissipation. These peculiar modes, usually referred to as “ghost waves”, hybridize the typical traits of conventional propagating and evanescent waves, displaying both phase accumulation and purely reactive exponential decay away from the direction of the power flow. Their existence has been predicted in several scenarios and has been recently observed experimentally in the form of surface phonon polaritons with complex-valued out-of-plane wavevectors propagating at the interface between air and a natural uniaxial crystal with slanted optical axis. Here, we demonstrate that ghost waves can arise also in lower-dimensional flat-optics scenarios, which are becoming increasingly relevant in the context of metasurfaces and in the field of polaritonics. Specifically, we show that planar junctions between isotropic and anisotropic metasurfaces can support “ghost line waves” that propagate unattenuated along the line interface, exhibiting phase oscillations combined with evanescent decay both in the plane of the metasurface (away from the interface) and out-of-plane in the surrounding medium. Our theoretical results, validated by finite-element numerical simulations, demonstrate a novel form of polaritonic waves with highly confined features, which may provide new opportunities for the control of light at the nanoscale and may find potential applications in a variety of scenarios, including integrated waveguides, nonlinear optics, optical sensing, and subdiffraction imaging.

Chiral Polaritonics: Analytical Solutions, Intuition, and Use.

Preferential selection of a given enantiomer over its chiral counterpart has become increasingly relevant in the advent of the next era of medical drug design. In parallel, cavity quantum electrodynamics has grown into a solid framework to control energy transfer and chemical reactivity, the latter requiring strong coupling. In this work, we derive an analytical solution to a system of many chiral emitters interacting with a chiral cavity similar to the widely used Tavis-Cummings and Hopfield models of quantum optics. We are able to estimate the discriminating strength of chiral polaritonics, discuss possible future development directions and exciting applications such as elucidating homochirality, and deliver much needed intuition to foster the newly flourishing field of chiral polaritonics.

Leaky Waves in Flatland

AbstractLeaky waves are complex eigenmodes compatible with radiation in terms of their momentum, which can be supported by open waveguiding structures and can be effective at modeling radiative phenomena from such systems. Here, a “flatland” analog of leaky‐wave radiation is introduced to describe a novel mechanism for in‐plane radiation leakage that can occur in artificial or natural low‐dimensional materials. Possible platforms are illustrated for its physical realization, in the form of suitably designed planar junctions of isotropic impedance surfaces that implement surface‐wave or line‐wave guiding structures. A simple and insightful semi‐analytical model for the radiation mechanism is developed and validated against full‐wave numerical simulations. These results provide a new tool for the advanced manipulation of surface waves at the nanoscale, which relies entirely on interface‐optics effects, and can find interesting applications in the emerging field of polaritonics.

Stepped metal gratings as an efficient way to design a broadband absorption efficiency and overcome recombination degradation in an organic solar cell

The Stepped stopped Groove Metal nano-grating (SSGMG) and Stepped Through Groove Metal nano-grating (STGMG) with a stepped hole transport layer (HTL) and a coating layer, is investigated as a novel method to obtain high absorption efficiency in a thin film organic solar cell. Enhancement of the electric field inside the gratings due to the near field and far-field coupling of wedge plasmon polaritons would lead to the improvement of the absorption efficiency of the solar cell. The proposed SSGMG model, with a 40 nm thickness of the photoactive layer, shows an absorption efficiency of 73.73% of the incident light in a wavelength range from 350 nm to 800 nm. the results show that the SSGMG model with an effective thickness of 40 nm has improved the absorption efficiency of the thickness-equivalent planar model (without coating layer) up to 133% of its initial value. Moreover, the effect of the incident angle (θ) and polarization angle (α) on the absorption efficiency was evaluated. We have found that SSGMG would lead to better absorption efficiency than STGMG because of its advantages over unpolarized light absorption. Excitation of surface plasmon polaritons inside the photo-active layer would help to reduce the recombination degradation as a result of the reduced thickness of the active layer as well as the enhanced mobility of charge. The designed structures can be used to overcome recombination degradation which is the intrinsic limitation of organic materials.

The Spin Texture Topology of Polygonal Plasmon Fields

Spin and field textures define the topology of the electric and magnetic fields in vacuum. These textures can be imposed on matter by light–matter interactions on the nanometer spatial and DC to femtosecond time scales to define the spatial and temporal symmetries of quasiparticle interactions. How to define the topology of thermodynamically evolving or dynamically imposed polaritonic textures is still an open question in applying control parameters such as temperature or phase of structured light. In this Perspective, we specifically consider the spin topology of geometrical plasmonic lattices formed by surface plasmon polariton fields spanning the full range of polygonal symmetries, ranging from the triangular to the circular including the intermediate aperiodic quasicrystalline tilings. Our premise is that the distortion of a triangular or a square lattice into a circular one, without introducing discontinuous geometric change, as by cutting, must preserve the polariton topology. From this perspective, we review the recent studies of stable optical field-induced dynamic quasiparticles with topological spin textures on the nanoscale. Specifically, we draw attention to how the topological spin textures evolve through the continuous deformation of the surface plasmon generating polygon geometries from triangular to circular. The goal of this Perspective is to introduce the topological properties of plasmonic vortices and to expand the discussion and understanding of how their topological spin and field textures dress material properties for exploration of fundamental physics and applications in photonics and spintronics.

Tomographic Reconstruction of Quasistatic Surface Polariton Fields.

We theoretically investigate the tomographic reconstruction of the three-dimensional photonic environment of nanoparticles. As input for our reconstruction we use electron energy loss spectroscopy (EELS) maps for different rotation angles. We perform the tomographic reconstruction of surface polariton fields for smooth and rough nanorods and compare the reconstructed and simulated photonic local density of states, which are shown to be in very good agreement. Using these results, we critically examine the potential of our tomography scheme and discuss limitations and directions for future developments.

Metasurfaces for Amplitude-Tunable Superposition of Plasmonic Orbital Angular Momentum States.

The superposition of orbital angular momentum (OAM) in a surface plasmon polariton (SPP) field has attracted much attention in recent years for its potential applications in classical physics problems and quantum communications. The flexible adjustment of the amplitudes of two OAM states can provide more freedom for the manipulation of superposed states. Here, we propose a type of plasmonic metasurface consisting of segmented spiral-shaped nanoslits that not only can generate the superposition of two OAM states with arbitrary topological charges (TCs), but also can independently modulate their relative amplitudes in a flexible manner. The TCs of two OAM states can be simultaneously modulated by incident light, the rotation rate of the nanoslits, and the geometric parameters of the segmented spiral. The relative amplitudes of the two OAM states are freely controllable by meticulously tuning the width of the nanoslits. Under a circularly polarized beam illumination, two OAM states of opposite TCs can be superposed with various weightings. Furthermore, hybrid superposition with different TCs is also demonstrated. The presented design scheme offers an opportunity to develop practical plasmonic devices and on-chip applications.