The excitation of localized or delocalized surface plasmon polaritons in nanostructured or extended graphene has attracted a steadily increasing attention due to their promising applications in sensors, switches, and filters. These single resonances may couple and intriguing spectral signatures can be achieved by exploiting the entailing hybridization. Whereas thus far only the coupling between localized or delocalized surface plasmon polaritons has been studied in graphene nanostructures, we consider here the interaction between a localized and a delocalized surface plasmon polariton. This interaction can be achieved by two different schemes that reside on either evanescent near- field coupling or far-field interference. All observable phenomena are corroborated by analytical considerations, providing insight into the physics and paving the way for compact and tunable optical components at infrared and terahertz frequencies.
Metasurfaces, with intrinsically planar nature and subwavelength thickness, provide us unconventional methodologies to not only mold the flow of propagating waves but also manipulate near-field waves. Plasmonic metasurfaces with topological transition for controlling surface plasmon polaritons (SPPs) recently have been experimentally demonstrated, which, however, are limited to optical frequencies. In this work, we proposed and experimentally characterized an ultrathin metasurface with the topological transition for manipulating spoof SPPs at low frequency. We demonstrated rich interesting phe…
Recent discoveries have shown that when two layers of van der Waals (vdW) materials are superimposed with a relative twist angle between their respective in-plane principal axes, the electronic properties of the coupled system can be dramatically altered. Here, we demonstrate that a similar concept can be extended to the optics realm, particularly to propagating polaritons, hybrid light-matter interactions. To do this, we fabricate stacks composed of two twisted slabs of a polar vdW crystal (MoO3) supporting low-loss anisotropic phonon polaritons (PhPs), and image the propagation of the latter…
Pseudorelativistic Dirac quasiparticles have emerged in a plethora of artificial graphene systems that mimic the underlying honeycomb symmetry of graphene. However, it is notoriously difficult to manipulate their properties without modifying the lattice structure. Here we theoretically investigate polaritons supported by honeycomb metasurfaces and, despite the trivial nature of the resonant elements, we unveil rich Dirac physics stemming from a non-trivial winding in the light-matter interaction. The metasurfaces simultaneously exhibit two distinct species of massless Dirac polaritons, namely …
Optical nonlinearities - how light-matter interactions are influenced by previous interactions with photons, are key resources in the contemporary photonics toolbox, relevant to quantum gate operations and all-optical switches. Optical nonlinearities of materials are often controlled at the microscopic level by chemical modification, which makes on-the-fly manipulation of such response challenging. Tunability of optical nonlinearities in the mid-IR is even less developed, hindering its applications in chemical sensing or IR photonic circuitry. Here, we report control of vibrational polariton c…
The formation of hybrid light-molecule states (polaritons) offers a new strategy to manipulate the photochemistry of molecules. To fully exploit its potential, one needs to build a toolbox of polaritonic phenomenologies that supplement those of standard photochemistry. By means of a state-of-the-art computational photochemistry approach extended to the strong-coupling regime, here we disclose various mechanisms peculiar of polaritonic chemistry: coherent population oscillations between polaritons, quenching by trapping in dead-end polaritonic states and the alteration of the photochemical reac…
The interaction of light with the localized/delocalized system, i.e., a metal surface with rectangular cavities of finite depth, has been studied. Reflection spectrum has been measured in the optical frequencies and resonant minima have been observed. We have developed an analytical model, which agrees well with the experiment. The localized waveguide resonance and delocalized surface resonance have been identified and discussed. The results may be useful for manipulating the coupling between light and matters.
We experimentally and theoretically study electromagnetic properties of optically thin silicon carbide (SiC) membranes perforated by an array of sub-wavelength holes. Giant absorption and transmission is found using Fourier Transformed Infrared (FTIR) microscopy and explained by introducing a frequency-dependent effective permittivity $ε_{\rm eff}(ω)$ of the perforated film. The value of $ε_{\rm eff}(ω)$ is determined by the excitation of two distinct types of hole resonances: a delocalized slow surface polariton (SSP) whose frequency is largely determined by the array period, and a localized …
Surface polaritons, e.g., surface plasmon polaritons, are invaluable tools in nanophotonics. However, considerable plasmon loss narrows the application regime of plasmonic devices. Here we reveal some general conditions for lossless surface polaritons to emerge at the interface of a gain and a loss media. The gain medium does not only compensate the energy loss, but also modifies surface wave oscillation mechanisms. A new type of surface polaritons induced by the sign switch of the imaginary part of the permittivity across the interface is discovered. The surface polaritons exhibit spin Hall e…
Strong interactions between surface plasmons in ultra-compact nanocavities and excitons in two dimensional materials have attracted wide interests for its prospective realization of polariton devices at room temperature. Here, we propose a continuous transition from weak coupling to strong coupling between excitons in MoS2 monolayer and highly localized plasmons in ultra-compact nanoantenna. The nanoantenna is assembled by a silver nanocube positioned over a gold film and separated by a dielectric spacer layer. We observed a 1570-fold enhancement in the photoluminescence at weak coupling regim…
We present theory to describe an engineering dispersion technique to obtain a broadband effective index near zero with an asymmetric planar photonic crystal. The theory provides the manipulating surface plasmon polariton (SPP) to provide alternating symmetric stacks of negative and positive effective indices. The odd alternating effective indices, including positive and negative refraction, arise from transverse resonance that depends on the geometry of the planar photonic crystal. The purposed technique remains wavepacket in zero phase dispersion since the created parity-time symmetries keep …
Twisted two-dimensional bilayer materials exhibit many exotic physical phenomena. Manipulating the twist angle between the two layers enables fine control of the physical structure, resulting in development of many novel physics, such as the magic-angle flat-band superconductivity, the formation of moire exciton and interlayer magnetism. Here, combined with analogous principles, we study theoretically the near-field radiative heat transfer (NFRHT) between two twisted hyperbolic systems. This two twisted hyperbolic systems are mirror images of each other. Each twisted hyperbolic system is compo…
We show that by manipulating quantum interference in a multi-atom cavity QED system, the nonlinear excitation of the cavity-atom polariton can be resonantly enhanced while the linear excitation is suppressed. Under appropriate conditions, it is possible to selectively enhance or suppress the polariton excitation with two free-pace laser fields. We report an experiment with cold Rb atoms in an optical cavity and present experimental results that demonstrate such interference control of the cavity QED excitation and its direct applications for studies of all-optical switching and cross-phase mod…
Integrating and manipulating the nano-optoelectronic properties of Van der Waals heterostructures can enable unprecedented platforms for photodetection and sensing. The main challenge of infrared photodetectors is to funnel the light into a small nanoscale active area and efficiently convert it into an electrical signal. Here, we overcome all of those challenges in one device, by efficient coupling of a plasmonic antenna to hyperbolic phonon-polaritons in hexagonal-BN to highly concentrate mid-infrared light into a graphene pn-junction. We balance the interplay of the absorption, electrical an…
The Purcell factor $F_p$ is a key quantity in cavity quantum electrodynamics (cQED) that quantifies the coupling rate between a dipolar emitter and a cavity mode. Its simple form $F_p\propto Q/V$ unravels the possible strategies to enhance and control light-matter interaction. Practically, efficient light-matter interaction is achieved thanks to either i) high quality factor $Q$ at the basis of cQED or ii) low modal volume $V$ at the basis of nanophotonics and plasmonics. In the last decade, strong efforts have been done to derive a plasmonic Purcell factor in order to transpose cQED concepts …
Strongly coupled light-matter systems can carry information over long distances and realize low threshold polariton lasing, condensation and superfluidity. These systems are highly non-equilibrium in nature, so constant nonzero fluxes manifest themselves even at the steady-state and are set by a complicated interplay between nonlinearity, dispersion, pumping, dissipation and interactions between the various constituents of the system. Based on the mean-field governing equations of lasers or polariton condensates, we develop a method for engineering and controlling the velocity profiles by mani…
Transformation optics has recently attracted extensive interest, since it provides a novel design methodology for manipulating light at will. Although transformation optics in principle embraces all forms of electromagnetic phenomena on all length scales, so far, much less efforts have been devoted to near-field optical waves, such as surface plasmon polaritons (SPPs). Due to the tight confinement and strong field enhancement, SPPs are widely used for various purposes at the subwavelength scale. Taking advantage of transformation optics, here we demonstrate that the confinement as well as prop…
Graphene plasmons are able to become the fundermental of novel conceptual photonic devices, resulting from their unique characteristics containing excitation at room temperature and tunable spectral selectivity in different frequencies. The pursuit of efficiently exciting and manipulating graphene plasmons is necessary and significant for high-performance devices. Here, we investigate graphene plasmon wave propagating in ferroelectric nanocavity array. We experimentally show that the the periodic ferroelectric polarizations could be used for doping graphene into desired spatial carrier density…
