Multiple Surface-plasmon-polariton Research Articles

Enhanced terahertz frequency mixing in all-dielectric metamaterial with multiple surface plasmon polaritons resonances

Nonlinear metamaterials hold a promising platform for generating terahertz (THz) waves. In this paper, we present an all-dielectric metamaterial with multiple surface plasmon polariton (SPP) resonances for enhanced THz frequency mixing. The metamaterial is composed of graphene ribbons, a dielectric layer, and a one-dimensional photonic crystal, displaying the multiple absorptions with simultaneous excitation of three SPP resonances. Taking advantage of SPP resonances with high Q factor and strong localized field at the input frequency, the third-order nonlinear processes are remarkably enhanced, including third-harmonic generation and four-wave mixing, producing a variety of frequencies in the THz range. The proposed efficient nonlinear metamaterials offer promising applications for THz frequency synthesis.

Multiple magnetoplasmon polaritons of magneto-optical graphene in near-field radiative heat transfer

Graphene, as a two-dimensional magneto-optical material, supports magnetoplasmon polaritons (MPP) when exposed to an applied magnetic field. Recently, MPP of a single-layer graphene has shown an excellent capability in the modulation of near-field radiative heat transfer (NFRHT). In this study, we present a comprehensive theoretical analysis of NFRHT between two multilayered graphene structures, with a particular focus on the multiple MPP effect. We reveal the physical mechanism and evolution law of the multiple MPP, and we demonstrate that the multiple MPP allow one to mediate, enhance, and tune the NFRHT by appropriately engineering the properties of graphene, the number of graphene sheets, the intensity of magnetic fields, as well as the geometric structure of systems. We show that the multiple MPP have a quite significant distinction relative to the single MPP or multiple surface plasmon polaritons (SPPs) in terms of modulating and manipulating NFRHT. We demonstrate that this remarkable behavior is attributed to the coupling between the significant contributions of surface states at multiple surfaces and Shubnikov–de Haas-like oscillations in the spectrum, indicating a transformation of intraband and interband transitions. Notably, we find that the evolution from single MPP to multiple MPP is absolutely different from that from single SPPs to multiple SPPs. Finally, a thermal magnetoresistance effect and a negative-positive transition of the relative thermal magnetoresistance ratio are predicted in the multilayered system under consideration. Our study paves the way for a flexible control of NFRHT and it offers the possibility for the thermal photon-based communication technology and a magnetically controllable thermal switch.

Observation of localized magnetic plasmon skyrmions

Optical skyrmions have recently been constructed by tailoring vectorial near-field distributions through the interference of multiple surface plasmon polaritons, offering promising features for advanced information processing, transport and storage. Here, we provide experimental demonstration of electromagnetic skyrmions based on magnetic localized spoof plasmons (LSP) showing large topological robustness against continuous deformations, without stringent external interference conditions. By directly measuring the spatial profile of all three vectorial magnetic fields, we reveal multiple π-twist target skyrmion configurations mapped to multi-resonant near-equidistant LSP eigenmodes. The real-space skyrmion topology is robust against deformations of the meta-structure, demonstrating flexible skyrmionic textures for arbitrary shapes. The observed magnetic LSP skyrmions pave the way to ultra-compact and robust plasmonic devices, such as flexible sensors, wearable electronics and ultra-compact antennas.

Twist-induced control of near-field thermal radiation in multilayered black phosphorus/vacuum system

Modulating the photonic transmission coefficient (PTC) is a critical factor in regulating the near-field radiative heat transfer (NFRHT) between two objects. Extending previous studies, we find that multiple body-vacuum interfaces can support various resonance modes and flexibly amplify the PTC. We show that black phosphorus (BP)/vacuum multilayers support coupled multiple anisotropic surface plasmon polaritons (MASPPs) and propose a theoretical model of a pattern-free noncontact thermal modulator based on the mechanical twist between two BP/vacuum multilayer structures. The various symmetric and antisymmetric branches of MASPPs strengthens the PTC, and with it the NFRHT. We also analyze the combined effects of the number of layers and twisted angle. Changing the integral twisted angle and inter-layer twisted angle modulates the positions and intensities of MASPPs. In addition to the twist between the emitter and receiver, the inter-layer twist gives the BP/vacuum multilayer heat transfer system another pathway to modulate the NFRHT. These results pave the way for using two-dimensional anisotropic materials to actively manipulate heat currents.

Enhancement and active mediation of near-field radiative heat transfer through multiple nonreciprocal graphene surface plasmons

Metasurfaces, the two-dimensional counterparts of three-dimensional metamaterials, have recently attracted much attention due to their interesting properties, such as negative refraction, hyperbolic dispersion, and the ability to manipulate the evanescent spectrum. In this work, we propose a theoretical model for near-field radiative heat transfer between two multilayered systems consisting of anisotropic metasurfaces. The choice of metasurface is graphene, with an adjustable drift current, since this provides an ideal platform to support a high density of modes around the plasmon frequency. In this configuration, multiple nonreciprocal surface plasmon polaritons are excited, providing a strong way for near-field energy transport. The resulting heat transfer, assisted by the graphene's multilayered structure and with a high drift-current velocity, is more than 36 times stronger than that of a graphene monolayer structure without a drift current for the same vacuum gap. By adjusting the vacuum gap and the thickness of a dielectric spacer, this enhanced effect can be modulated over a large range, and can even turn into a suppression. Our findings provide a powerful way to enhance and regulate energy transport, and in turn, open up a way to enrich the moir\'e physics inherent to the anisotropic optical properties of a metasurface.

Interaction and hybridization of orthogonal Fabry-Pérot like surface plasmon modes in metal-dielectric grating structures

The interaction of specific surface plasmon modes in metal-dielectric-metal arrangements is investigated, motivated by their relevance to device-based configurations. The absorption spectra of the relevant nanostructures considering geometrical variation, such as the width and height of the metal or dielectric, are probed considering such interactions. Frequency domain simulations are used to study related multiple surface plasmon polariton resonance modes. It is indicated that the resonant energy level interaction due to the coupling between modes in a horizontal dielectric layer and those in a vertical groove can be engineered and understood in terms of energy level hybridization.

Graphene-based thermal repeater

In this Letter, we have demonstrated the possibility to efficiently relay the radiative heat flux between two nanoparticles by opening a smooth channel for heat transfer. By coating the nanoparticles with a silica shell and modifying the substrate with multilayered graphene sheets, respectively, the localized phonon polaritons excited near the nanoparticles can couple with the multiple surface plasmon polaritons near the substrate to realize the heat relay at a long distance. The heat transfer can be enhanced by more than six orders of magnitude, and the relay distance can be as high as 35 times in the far-field regime. This work may provide a way to realize the energy modulation or thermal communications especially at long distances.

On the Propagation of Multiple Surface Plasmon-Polariton Waves by a Triangle Helix Thin Film in Sarid Configuration

Increasing the propagation length of surface plasmon polariton waves has always been a problem in the field of plasmonics. Here, we reported that the surface plasmon polariton waves are multiplied by considering a central metal defect in a dielectric triangle helix thin film using Sarid configuration. The dependence relative phase speed and propagation length of the multiple surface plasmon polariton waves on different structural parameters are investigated. The results showed that the high propagation length up to 236 μm is made available by selecting suitable structural parameters. The localization of surface plasmon polariton waves is proven by the depiction of the time-averaged Poynting vector and local absorption as a function of depth of the structure.

Optical fishnet metamaterial with negative, zero, positive refractive index and nearly perfect absorption behavior at different frequencies

Metamaterials (MMs) have many novel characteristics with the aid of appropriate structural design. In this study, we report negative refractive index (NRI), zero refractive index (ZRI) and nearly perfect absorption (NPA) characteristics of an optical fishnet structure. Base on the S-parameter retrieval theory, this periodic nano tapered holes fishnet structure that has simultaneously negative permittivity and negative permeability and shows NRI characteristic from 553 THz to 600 THz. The fishnet structure also exhibits a seamless transition between the negative and positive refractive index bands with a zero index at the transition frequency of 600 THz. Moreover, interestingly, a broadband nearly perfect absorption (NPA) characteristic above 95% arises in 650 THz to 700 THz. As mentioned characteristics of NRI, ZRI and NPA above, they are gained from local electromagnetic fields enhancement by the multiple surface plasmon polaritons (SPPs) resonance mechanism.

Multiple surface plasmon polaritons mediated near-field radiative heat transfer between graphene/vacuum multilayers

Modulating the photon tunneling probability is the key to control the near-field radiative heat transfer (NFRHT) between two objects. It has been found that multiple body-vacuum interfaces can enable plentiful resonance modes which significantly amplify photon tunneling probability. In the present paper we demonstrate that a graphene/vacuum multilayers can support coupled multiple surface plasmon polaritons (MSPPs), not only enhancing but also suppressing the photon tunneling, hence the NFRHT. We demonstrate that, due to the plentiful symmetric and anti-symmetric branches produced by the coupling of MSPPs, enhancement of NFRHT is most prominent as the middle gap is comparable to the separation distance. Moreover, by adjusting the separation distances, number of layers and chemical potentials, several interesting phenomena are observed in the multilayers, hence providing more possibilities to modulate NFRHT. We find that the optimized enhancement of heat transfer exhibits a 1/d dependency, which means that compared to the bulk system, the decline of NFRHT in the multilayers versus gap width is delayed. This phenomenon has never been noted in a graphene or graphene-based system before. With a large separation distance, the enhanced heat transfer of multilayer over single layer is weak, even vanishes. As the separation distance is far below the gap width, the multilayer system reveals an apparent suppressed of heat transfer. While this suppression effect can be switched into enhancement one by adjusting the chemical potential to a large value. Physical mechanism behind the above findings is understood in detail by analyzing the photon tunneling probabilities and reflection coefficients. This work can be instructive for both experimental design and fabrication of thermal radiation devices based on graphene.

Fast and slow propagations of surface plasmon polaritons on metallic mesh gratings

Surface plasmon polariton (SPP) generations on silver-based metal–insulator–metal (MIM) cross mesh gratings were studied by polychromatic and monochromatic specular reflection. Centimeter area scale mesh grating samples were made using soft-lithography imprinting with a varied micro-sized array pitch. The mesh structures support multiple SPP orders with a periodicity-influenced mode generation. For the (±1, 0) SPP modes steep dispersions thus high SPP group velocities Vg were obtained over an extended wavelength range of propagation. Vg were found to achieve a maximum at frequencies closer to the mesh periodicity.

Excitation of Multiple Surface Plasmon-Polaritons by a Metal Layer Inserted in an Equichiral Sculptured Thin Film

Excitation of multiple surface plasmon-polaritons(SPPs) by an equichiral sculptured thin film with a metal layer defect was studied theoretically in the Sarid configuration, using the transfer matrix method. Multiple SPP modes were distinguished from waveguide modes in optical absorption for p- polarized plane wave. The degree of localization of multiple SPP waves was investigated by calculation of the time averaged Poynting vector. The results showed that the long-range and short-range SPP waves can simultaneously be excited at both interfaces of metal core in this proposed structure which may be used in a broad range of sensing applications.

Differentiating surface plasmon-polariton waves and waveguide modes guided by interfaces with one-dimensional photonic crystals

One-dimensional photonic crystals (PCs) are made of planar layers of different materials with periodic arrangement. Such PCs can support multiple surface waves at their interfaces with homogeneous materials as well as multiple waveguide modes guided by individual constituent layers. The numerical results comparing multiple surface plasmon-polariton (SPP) waves and waveguide modes guided by a metal and a PC with only two layers in each period indicated that the periodic nonhomogeneity and the waveguide modes guided by the individual layers in the PC engender the multiplicity of SPP waves. For smaller value of the period of the PC, the coupling of the individual layers in the PC near the metal/PC interface gives rise to new SPP waves but the coupling reduces as the period increases and waveguide modes dominate. The differentiation between the waveguide modes and the surface waves is necessary to fully exploit the promise of photonic crystals in integrated optics.

A highly sensitive multiplasmonic sensor using hyperbolic chiral sculptured thin films

Surface plasmon-polariton (SPP) waves guided by an interface of a metal and a hyperbolic chiral sculptured thin film (STF) were theoretically investigated for optical sensing of an analyte. The chiral STF was infiltrated with the analyte to be sensed, and the resulting change in the incidence angle of excitation of the SPP waves in the prism-coupled configuration was computed. The results indicated the potential of this configuration for a plasmonic sensor with sensitivity up to 6000 degrees per refractive index units of the infiltrating fluid in the angular investigation scheme, with multiple SPP waves of the same frequency but different phase speeds, spatial profiles, and sensitivities. The enhancement in the sensitivity is attributed to the high field strength of the SPP waves near the interface. A multiplasmonic sensor is advantageous because of its potential for higher confidence in the measurement of the same analyte.

Multiple surface-plasmon-polariton waves guided by a chiral sculptured thin film grown on a metallic grating

Theoretical and experimental studies were undertaken to investigate the grating-coupled excitation of multiple surface-plasmon-polariton (SPP) waves guided by the periodically corrugated interface of a metal and a chiral sculptured thin film (STF). The rigorous coupled-wave approach was adapted to calculate the absorptance spectrum of a structure comprising a chiral STF atop a rectangular metallic grating when that structure is illuminated by a linearly polarized plane wave whose wavevector lies wholly in the corrugation plane. The incidence direction could be either normal or oblique with respect to the thickness direction of the structure. High-absorptance bands for both s- and p-polarized incident plane waves were found to be correlated with the SPP wavenumbers calculated from the solution of the underlying canonical boundary-value problem, indicating that multiple distinct SPP waves can be excited at a specific frequency. The resistive-heating thermal evaporation technique was used to deposit chiral STFs of zinc selenide on gold gratings made by electron-beam lithography, and transmittance and reflectance spectra of the fabricated structures were measured in a variable-angle spectroscopic system in order to qualitatively validate the theoretical understanding. Several high-absorptance bands were found to be almost unaffected by the number of periods of the chiral STF. The existence of these bands indicated that as many as three distinct SPP waves were excited at a specific frequency in several spectral regimes by s- and/or p-polarized incident light.

Interference of Multiple Surface Plasmon Polaritons

Benefiting from strongly electromagnetic confinement and enhancement effects, surface plasmon polaritons (SPPs) hold great promises for tailoring light on micro and nanoscale. By contrast with previous efforts which massively concentrate on localized SPP mode, we investigated the propagating SPPs in this paper. A number of symmetrical gratings on metal surface are employed to excite multiple SPPs. Interestingly, the exotic interfering phenomena have been observed. They show good agreement with free-space interferences and take advantage of precise controllability. These findings will be promising in the applications of optical tweezers and SPP lithography.

Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a structurally chiral material

Multiple compound surface plasmon-polariton (SPP) waves can be guided by a structure consisting of a sufficiently thick layer of metal sandwiched between a homogeneous isotropic dielectric (HID) material and a dielectric structurally chiral material (SCM). The compound SPP waves are strongly bound to both metal/dielectric interfaces when the thickness of the metal layer is comparable to the skin depth but just to one of the two interfaces when the thickness is much larger. The compound SPP waves differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. Some compound SPP waves are not greatly affected by the choice of the direction of propagation in the transverse plane but others are, depending on metal thickness. For fixed metal thickness, the number of compound SPP waves depends on the relative permittivity of the HID material, which can be useful for sensing applications.

Enhancement of Dynamic Sensitivity of Multiple Surface-plasmonic-polaritonic Sensor Using Silver Nanoparticles

Multiple surface plasmon-polariton (SPP) waves excited at the interface of a homogeneous isotropic metal and a chiral sculptured thin film (STF) impregnated with silver nanoparticles were theoretically assessed for the multiple-SPP-waves-based sensing of a fluid uniformly infiltrating the chiral STF. The Bruggemann homogenization formalism was used in two different modalities to determine the three principal relative permittivity scalars of the silver-nanoparticle-impregnated chiral STF infiltrated uniformly by the fluid. The dynamic sensitivity increased when silver nanoparticles were present, provided their volume fraction did not exceed about 1%.

Experimental excitation of multiple surface-plasmon-polariton waves and waveguide modes in a one-dimensional photonic crystal atop a two-dimensional metal grating

The excitation of multiple SPP waves as Floquet harmonics was demonstrated in structures fabricated as one-dimensional photonic crystals (PCs) on top of two-dimensional gold gratings. Each period of the PC comprised nine layers of silicon oxynitrides of different compositions, and each PC had either two or three periods. Absorptances for obliquely incident $p$- and $s$-polarized light were measured in the 500--1000-nm wavelength regime and the sharp bands in the absorptance spectra were compared with the solutions of the underlying canonical boundary-value problem. The excitation of multiple surface-plasmon-polariton (SPP) waves as Floquet harmonics was confirmed. The structures demonstrated broadband absorption with overall weak dependences on the incidence angle and the polarization state of the incident light, and has potential application for harvesting solar energy.

Multiplasmonic Optical Sensor Using Sculptured Nematic Thin Films

Fluid-infiltrated sculptured nematic thin films (SNTFs) were modeled using a combination of piecewise uniform approximation technique and Bruggeman formalism. The modeling was then used to exploit surface plasmon-polariton (SPP) waves for optical sensing of the fluid infiltrating the SNTF. The interface of the chosen metal and the SNTF supports multiple SPP waves of the same frequency, thereby, providing multiple angles of incidence in the prism-coupled configuration for optical sensing, offering potential for a higher confidence in measurements and multi-analyte sensing at the same time.