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We theoretically investigate the light-induced excitation of two-dimensional surface polaritons (2DSPs) at the edge of atomically thin crystals. Through our analytic model based on the coupled mode theory, we achieve a precise and quantitative description of light interaction with the crystal's edge. Our model unveils three notable properties associated with the edge-excitation of 2DSPs. Firstly, under strong confinement conditions (i.e., polariton momentum significantly surpassing free-space photon momentum), the amplitude of edge-excited 2DSPs exhibits a cosine dependency on the incident angle. Secondly, the amplitude reaches a saturation point at a specific value as polariton momentum increases, depending on the incident angle. Lastly, we demonstrate that the edge-excitation of 2DSPs entails the generation of induced unbounded waves near the edge, leading to peak oscillations due to the interference between the 2DSPs and the unbounded waves.

Owning to their unusual optical properties, such as electrical tunability and strong spatial confinement, two-dimensional surface polaritons (2DSPs) hold great promise for deep sub-wavelength manipulation of light in a reduced low-dimensional space. Control of 2DSPs is possible by using their interaction with a boundary between two media, similar to how light behaves in three-dimensional (3D) space. The understanding of the interaction in the 2D case is still in its early stages, unlike the 3D case, as in-depth investigations are only available in a few cases including the interaction of 2DSPs with structured 2D crystals. Here, we extend the scope of our understanding to the interaction of 2DSPs with metallic nano-plates on 2D crystals, focusing on the reflection of 2DSPs. Through our rigorous model, we reveal that, for strongly confined 2DSPs having much larger momentum than free space photons, the interaction results in almost total internal reflection of 2DSPs as the radiative coupling of the 2DSPs to free space is negligible. We also find that the reflection involves an anomalous phase shift dependent on the thickness of the nano-plate, due to the temporary storing of electromagnetic energy in the evanescent waves induced near the edge of the nano-plate. Our theory predicts that the phase shift saturates to an anomalous value, 0.885π, as the nano-plate becomes thicker. Our work provides a detailed understanding of how to manipulate the 2DSPs by using one of the simplest nanostructures, essential for the further development of nanostructure-integrated low-dimensional devices for polariton optics.

Enhancement of weak Casimir forces is extremely important for their practical detection and subsequent applications in variety of scientific and technological fields. We study the lateral Casimir forces acting on the rotating particles with small radius of 50 nm as well as that with large radius of 500 nm near the hyperbolic metamaterial made of silicon carbide (SiC) nanowires. It is found that the lateral Casimir force acting on the small particle of 50 nm near hyperbolic metamaterial with appropriate filling fraction can be enhanced nearly four times comparing with that acting on the same particle near SiC bulk in the previous study. Such enhancement is caused by the coupling between the resonance mode excited by nanoparticle and the hyperbolic mode supported by hyperbolic metamaterial. The results obtained in this study provide an efficient method to enhance the interaction of nanoscale objects. [ABSTRACT FROM AUTHOR]

In this paper, surface polaritons (SPs) at the interface of a semi-infinite homogeneous dielectric medium and a one-dimensional photonic crystal (PC) have been investigated theoretically. The PC is made of the alternate layers of an isotropic ordinary dielectric and a graphene-based hyperbolic metamaterial layers. The effective medium approach has been used for the study of the metamaterial layers and it is shown that they have hyperbolic dispersion in a certain frequency range at THz region. The obtained results show that the structure has some photonic band gaps in the hyperbolic and elliptical frequency regions for both TE and TM polarizations and can support the SPs in these frequency ranges. It is observed that the characteristics of the SPs depend on the geometrical parameters of the structure and optical parameters of the graphene monolayers. In the following, the electromagnetic field profiles of some SPs have been plotted and it is shown that the modes of the first band gap are more localized than the modes of the second band gap. Finally, the intensity distribution of a TM-polarized Gaussian beam inside and outside the PC has been simulated which is verifying the localization of the SPs at the interface of the structure.

Near-field radiative heat transfer (NFRHT) can exceed the blackbody limit by several orders of magnitude owing to the tunneling evanescent waves. Exploiting this near-field enhancement holds significant potential for emerging technologies. It has been suggested that coupled polaritons can give rise to orders of magnitude enhancement of NFRHT. However, a thorough experimental verification of this phenomenon is still missing. Here this work experimentally shows that NFRHT mediated by coupled polaritons in millimeter-size graphene/SiC/SiO 2 composite devices in planar plate configuration can realize about 302.8 ±  35.2-fold enhancement with respect to the blackbody limit at a gap distance of 87  ±  0.8 nm. The radiative thermal conductance and effective gap heat transfer coefficient can reach unprecedented values of 0.136 WK -1 and 5440 Wm -2 K -1 . Additionally, a scattering-type scanning near-field optical measurement, in conjunction with full-wave numerical simulations, provides further evidence for the coupled polaritonic characteristics of the devices. Notably, this work experimentally demonstrates dynamic regulation of NFRHT can be achieved by modulating the bias voltage, leading to an ultrahigh dynamic range of ≈4.115. This work ambiguously elucidates the important role of coupled polaritons in NFRHT, paving the way for the manipulation of nanoscale heat transport, energy conversion, and thermal computing via the strong coupling effect., (© 2024 Wiley‐VCH GmbH.)

The dynamic heat transfer between two half-spaces separated by a vacuum gap due to the coupling of their surface modes is modeled using the theory that describes the dynamic energy transfer between two coupled harmonic oscillators, each separately connected to a heat bath and with the heat baths maintained at different temperatures. The theory is applied for the case when the two surfaces are made up of a polar crystal that supports surface polaritons that can be excited at room temperature and the predicted heat transfer is compared to the steady-state heat transfer value calculated from the standard fluctuational electrodynamics theory. It is observed that for small time intervals the value of heat flux can be significantly higher than that of steady-state value.

• Investigation of near-field radiative heat transfer between moving two-dimensional anisotropic surfaces. • Derivation of near-field thermal radiation formulas between moving anisotropic surfaces based on the theory of fluctuating dissipative electrodynamics theory combined with Lorentz transformation. • Exploring the coupling of rotation angles with moving 2D anisotropic surface models. • Exploring the energy transfer coefficient between anisotropic moving surfaces as affected by parameters such as separation distance and electron density. • Provides a new idea for the active regulation of near-field radiative heat transfer. Radiation heat transfer from two-dimensional anisotropic materials has promising applications in nanodevices, such as non-contact thermal modulators, thermal lithography and thermophotovoltaics. Moving surface is expected to provide more possibilities for the modulation of near-field thermal radiation due to its special properties such as supporting hyperbolic propagation and non-reciprocity. In this study, the near-field radiative heat transfer between moving anisotropic surfaces is investigated in the framework of the fluctuation-dissipation electrodynamics theory combined with the Lorentz transformation. It is found that the movement and rotation of the surface lead to the asymmetry of energy transfer in the wave vector space, which affects the energy transfer coefficient and hence the radiation heat flux. The effect of velocity, separation distance, rotation angle and electron density on the energy transfer coefficient and radiative heat flux between moving anisotropic surfaces is revealed. It is found that the heat flux decreases as the velocity increases, the sensitivity of the heat flux variation with velocity decreases as the velocity increases. This study provides a new idea for the active regulation of near-field radiative heat transfer. [ABSTRACT FROM AUTHOR]

• Light interaction with the edge of a two-dimensional crystal has been theoretically studied. • A rigorous analytic model has been developed. • The incident-angle-dependent excitation efficiency of two-dimensional polaritons has been determined. • The unique formation of the near-field profiles has been revealed. We theoretically investigate the light-induced excitation of two-dimensional surface polaritons (2DSPs) at the edge of atomically thin crystals. Through our analytic model based on the coupled mode theory, we achieve a precise and quantitative description of light interaction with the crystal's edge. Our model unveils three notable properties associated with the edge-excitation of 2DSPs. Firstly, under strong confinement conditions (i.e., polariton momentum significantly surpassing free-space photon momentum), the amplitude of edge-excited 2DSPs exhibits a cosine dependency on the incident angle. Secondly, the amplitude reaches a saturation point at a specific value as polariton momentum increases, depending on the incident angle. Lastly, we demonstrate that the edge-excitation of 2DSPs entails the generation of induced unbounded waves near the edge, leading to peak oscillations due to the interference between the 2DSPs and the unbounded waves. [ABSTRACT FROM AUTHOR]

The reflection and attenuated total reflection spectra of aluminum and gallium nitride films doped with silicon on sapphire substrates with a buffer layer of aluminum nitride have been measured. In the spectra of attenuated total reflection, surface phonon and plasmon–phonon polaritons were observed. A high concentration of charge carriers in the gallium nitride film and their practical absence in the aluminum nitride film were experimentally observed. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance has become a widely accepted optical technique for studying biological and chemical interactions. Among others, detecting small changes in analyte concentration in complex solutions remains challenging, e.g., because of the need of distinguishing the interaction of interest from other effects. In our model study, the resolution ability of plasmonic sensing element was enhanced by two ways. Besides an implementation of metal-insulator-metal (MIM) plasmonic nanostructure, we suggest concatenation with waveguiding substructure to achieve mutual coupling of surface plasmon polariton (SPP) with an optical waveguiding mode. The dependence of coupling conditions on the multilayer parameters was analyzed to obtain optimal field intensity enhancement.

In this work, we developed a unique mathematical model to solve dispersion relation for surface polaritons (SPs) in artificial composite materials grating. Here, we have taken two types of materials for analysis. In the first case, the grating composed of epsilon-negative (ENG) material and air interface. In second case, grating composed of left-handed materials (LHMs) and ENG medium interface is considered. The dispersion curves of both p and s polarized SPs modes are obtained analytically. In the case of ENG grating and air interface, polaritons dispersion curves exist for p-polarization only, whereas for LHM grating and ENG medium interface, the polaritons dispersion curves for both p and s polarization are observed. [ABSTRACT FROM AUTHOR]

Here we report on the analysis of the effect of the doping of CdP single crystals by ZnP nanoclusters on the dispersion of the surface polaritons (SP). The ATR spectroscopic technique has been applied to excite the SP in the CdZnP system. Analysis of the obtained spectra has shown that the doping of CdP single crystals by ZnP nanoclusters result in the position and the width of the dispersion branches of the SP. This effect is more pronounced in the low frequency dispersion branches. These SP branches are originated from phonons which correspond to the motion of the cation sublattice. [ABSTRACT FROM AUTHOR]

The calculations of the real and imaginary part of complex dielectric constant of bulk Ti is produced by the first principles. Using the SIESTA program, the simulating of the interaction of light with substance is carried out. For a Ti layer the reflection frequency angle spectra have been analyzed in the ATR configuration. The surface polaritons may be generated in this case.

An investigation of the infrared (IR) spectra of polyoxymethylene (POM) mold plates was undertaken to determine the sub-micron-scale morphology and molecular orientation. The nest-structured cells concerned with the orientation were observed from scanning electron microscope (SEM) measurements with the aid of Raman spectroscopy. The intensity of the anomalous IR reflectance peak of the C-O stretching A2 mode depends on the widths of the POM layers in the SEM image along the orientation direction. The results suggest that the spectral features originate from the Berreman effect of the bulk polaritons and the radiative surface polaritons. Moreover, the IR spectra of certain treated samples suggest that enhancement of the electromagnetic fields from the gap modes and transition dipole-dipole coupling influence the spectral shapes. [ABSTRACT FROM AUTHOR]

Zinc diphosphide Zn 3 P 2 is promising material for photovoltaic applications due to its physical properties. In this study dispersion of the surface polaritons ν s (k) in Zn 3 P 2 has been investigated at 10 and 300 K. Surface polaritons were excited using method of attenuated total reflection (ATR) spectroscopy. Influence of the temperature on the dispersion of the surface polaritons ν s (k) in Zn 3 P 2 is analyzed and discussed. [ABSTRACT FROM AUTHOR]

The fascinating capability of manipulating light using metamaterials (MMs) has inspired a significant amount of studies of using MMs for energy related applications. In this work we investigate MM-based perfect absorbers for enhancing near field radiative heat transfer, which is described by the fluctuation dissipation theorem. MM structures designed at two wavelengths are analyzed, corresponding to two working temperatures. Both electric and magnetic surface polaritons are found to contribute to heat transfer, while natural materials support only electric polaritons. The near-perfect absorption is demonstrated to be related to the modification of effective optical properties, which is important for enhancing radiative heat transfer efficiently. By comparing different designs, the bandwidth of the heat flux spectrum is found to increase with the absorption bandwidth, which is originated from the spatial field distributions. This study will contribute to the understanding of surface polaritons in near field radiative heat transfer and facilitate the optimization of MMs for near field heat transfer applications. [ABSTRACT FROM AUTHOR]

The features of the surface polaritons propagation are studied at the interface of an enhanced isotropic dielectric and a nanocomposite media with spherical metal inclusions. For each media, the frequency dependences of the propagation constant and the wave vector transverse components, group velocity and path length, penetration depth and longitudinal energy flow have been obtained and represented by diagrams. A significant impact of the imaginary part of dielectric permittivity on the wave characteristics of surface polaritons has been shown. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we consider different waveguide structures comprising a metal and a dispersive negative index material (NIM) which has negative permittivity and permeability over a frequency band in the microwave range of several GHz. In the first structure, one interface separating a semi-infinite metal and a semi-infinite NIM is assumed. In the second structure, a NIM slab is sandwiched between a metal and a dielectric material whereas in the third structure a metal slab is embedded in a NIM medium. The dispersion relations and the conditions for surface polariton excitation at the interfaces are derived, plotted and discussed. Penetration depth and modal refractive index are also studied. [Copyright &y& Elsevier]

Due to ultrabright and stable blue light emission, GaN has emerged as one of the most famous semiconductors of the modern era, useful for light-emitting diodes, power electronics, and optoelectronic applications. Extending GaN's optical resonance from visible to mid- and-far-infrared spectral ranges will enable novel applications in many emerging technologies. Here we show hexagonal honeycomb-shaped GaN nanowall networks and vertically standing nanorods exhibiting morphology-dependent Reststrahlen band and plasmon polaritons that could be harnessed for infrared nanophotonics. Surface-induced dipoles at the edges and asperities in molecular beam epitaxy-deposited nanostructures lead to phonon absorption inside the Reststrahlen band, altering its shape from rectangular to right-trapezoidal. Excitation of such surface polariton modes provides a novel pathway to achieve far-infrared optical resonance in GaN. Additionally, surface defects in nanostructures lead to high carrier concentrations, resulting in tunable mid-infrared plasmon polaritons with high-quality factors. Demonstration of morphology-controlled Reststrahlen band and plasmon polaritons make GaN nanostructures attractive for infrared nanophotonics.

The hybridization of surface plasmon polaritons and hyperbolic phonon polaritons in graphene/hBN heterostructures has been well documented to achieve very high radiative heat flux transferred in the near field, paving the way for wide applications ranging from energy harvesting, non-contact thermal management to thermal imaging. However, previous related theoretical studies mainly focused on suspended structures. When it comes to the experimental implementation, a supporting substrate is quite a necessity for this kind of 2D layered heterostructures to ensure structural stability. Herein, the near-field radiative heat transfer (NFRHT) between bi-planar graphene/hBN heterostructures was revisited by integrating them with various substrates, including Au, SiC, and silica, under the framework of the fluctuation-dissipation theorem. The results show that each substrate exerts significant impacts either further enhancing or suppressing the NFRHT between those bi-planar heterostructures, due to the competition between polaritonic couplings and dielectric losses. Whereas, these substrate effects depend on the hBN thickness with a critical length, beyond which the hBN itself is thick enough to indiscriminately screen all these effects. The findings in this study will be instructive to both the experimental designs and device integrations for graphene-based NFRHT applications. [ABSTRACT FROM AUTHOR]

Abstract: Surface polaritons have been used to study the nitridation of sapphire substrates. The samples of nitridized sapphire were prepared by gas source molecular beam epitaxy with ammonia, and the nitridation process was controlled by reflection high energy electron diffraction. The external reflectivity infrared spectra at near normal incidence are not sensitive to the nitridation. On the other hand, the high-frequency minimum in the attenuated total reflection spectra splits near 700cm−1 due to the presence of aluminum nitride on the substrate surface, demonstrating high sensitivity of the surface polariton technique to the state of the surface. [Copyright &y& Elsevier]

Surface polariton spectra of magnesium oxide films (of thickness ranging from 10 to 300 nm) prepared by chemical vapor deposition technique on sapphire substrates have been studied. The splitting of the dispersion curve of the sapphire surface polariton appears near 700 cm due to the resonance interaction of the sapphire substrate surface polariton with the film optical phonon. This splitting is proportional to the square root of the film thickness. Optical constants of ultrathin magnesium oxide films have been obtained from surface polariton spectra measurements. For the thinnest film (10 nm) they appear to be close to the bulk crystal values. [ABSTRACT FROM AUTHOR]

Abstract: The dispersive characteristics of surface plasmon polaritons (SPPs) supported by a periodically corrugated boundary between vacuum and a negative refractive index, isotropic material were studied theoretically by numerical solution of a dispersion equation. SPP dispersion curves were correlated with the optical response of the corrugated boundary in frequency regions where SPPs can be excited by a normally incident plane wave. Abrupt reflectivity variations, characterized by the presence of a near unity maximum and an almost zero minimum, were found in regions where the boundary without corrugation exhibits low reflectivity and rather featureless reflectivity curves. [Copyright &y& Elsevier]

Abstract: Various theoretical methods to calculate the spectral and correlation properties of fluctuating electromagnetic fields generated by solids are reviewed, all of which essentially reduce to solving the Maxwell equations for a specified geometry and boundary conditions and then using the fluctuation–dissipation theorem. The spectral and correlation properties of thermally stimulated fields of a system in equilibrium and out of equilibrium with surrounding bodies are described. A special attention is put to the difference between the spectral and correlation properties of the propagating and evanescent waves of the thermally stimulated fields of solids. The dispersion interaction between solid bodies in different thermodynamic states, the resonance dispersion interaction in a three-body system, the fluctuating fields as a means of body-to-body energy transfer, and the shift, broadening, and deexcitation of energy levels in a particle near a solid surface are discussed using the theory of thermally stimulated electromagnetic fields. Thermally stimulated emission of infrared radiation of semiconductor crystals and films (heated up to 150 °C) on metal substrates are measured in frequency range of vibrational polaritons both for propagating waves and for evanescent waves transformed into propagating waves due to ATR prism over the samples. The experimental results on thermally stimulated electromagnetic fields from solids are in qualitative and quantitative agreement with model calculations and theoretical expectations. [Copyright &y& Elsevier]

Abstract: The near field heat transfer between two finite size one-dimensional photonic crystals separated by a small vacuum gap and maintained in nonequilibrium thermal situation is theoretically investigated. The main features of this electromagnetic transfer are discussed and compared with what is generally observed with media that support surface polaritons. It is shown that the presence of surface Bloch waves can significantly enhance heat transfers beyond the far field limit for both polarization states of electromagnetic field at subwavelength separation distances. A specific attention is addressed to the consequence of the slopes of surface Bloch waves dispersion curves on the heat transfer. In particular, it is shown that the localization of surface Bloch waves close to the light line allows to observe a transfer exaltaion at larger separation distances than the Wien wavelength. These results could open new possibilities for the development of innovative near-field technologies such as near-field thermophotovoltaic conversion, plasmon assisted nanophotolitography or near-field spectroscopy. [Copyright &y& Elsevier]

Abstract: To obtain the eigenmodes of the electromagnetic field at a periodically corrugated metamaterial we consider the analytic extension to the complex plane of the solution to the boundary-value problem for a metamaterial grating. We build a proper Riemann sheet for these eigenmodes and we present numerical examples illustrating their propagation characteristics. Particularly, we pay special attention to regimes corresponding to ideally transparent metamaterials with a negative index of refraction, where the eigenmodes can radiate into the metamaterial medium. [ABSTRACT FROM AUTHOR]

We demonstrate that mid-infrared surface phonon polariton excitation, propagation and interference can be studied by scattering-type near-field optical microscopy (s-SNOM). In our experiments we image surface phonon polaritons (SPPs) propagating on flat SiC crystals. They are excited by weakly focused illumination of single or closely spaced metal disks we fabricated on the SiC surface by conventional photolithography. SPP imaging is performed by pseudo-heterodyne interferometric detection of infrared light scattered by the metal tip of our s-SNOM. The pseudo-heterodyne technique simultaneously yields optical amplitude and phase images which allows us to measure the SPP wave vector – including its sign – and the propagation length and further to study SPP interference. High resolution imaging of SPPs could be applied to investigate for example SPP focusing or heat transfer by SPPs in low dimensional nanostructures. [ABSTRACT FROM AUTHOR]

Surface and proper leaky modes guided by a grounded pseudochiral omega slab are studied. A new physical result is found: proper leaky modes may occur in a lossless grounded pseudochiral omega slab even when all medium parameters are positive. A correlation between polaritons at interfaces and leaky modes in slab waveguides is established. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 814–818, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23220 [ABSTRACT FROM AUTHOR]

Surface polaritons are guided electromagnetic waves propagating along a single interface, with the amplitude of the field decreasing along the direction that is normal to the interface. These modes can propagate along interfaces separating a conventional (double-positive) isotropic medium either from a single-negative or from a double-negative medium. They were also found to propagate along isotropic–uniaxial and isotropic–biaxial interfaces. In this paper we show, for the first time, that surface polaritons can also occur at an interface between air and a pseudochiral omega medium. It is also shown, furthermore, that proper leaky-modes can also exist in this special type of isotropic–bianisotropic interface—a completely new physical effect for a single interface between two lossless media. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2517–2520, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22009 [ABSTRACT FROM AUTHOR]

Abstract: Scattering of surface plasmon polaritons (SPP’s) by small ellipsoid particles placed near a dielectric–metal interface is theoretically considered. Using the Green’s function formalism and the dipole approximation, we consider the differential and total scattering cross-sections associated with the SPP-to-SPP scattering as well as with the SPP scattering into waves propagating away from the interface, analyzing the influence of system parameters. As an example, scattering cross-sections of differently shaped gold spheroid particles placed near an air–gold interface are evaluated at the light wavelength of 800nm. It is shown that the differential and total cross-sections depend strongly upon the particle-to-surface distance, the ratio between the major and minor axes and their orientation with respect to both the interface and the direction of SPP incidence. Implications of the obtained results to the design of SPP micro-optical components are also discussed. [Copyright &y& Elsevier]