Excitation Of Surface Plasmon Polaritons Research Articles

Directional switching of surface plasmons in a parity-time-symmetric insulator-metal-insulator structure

In the present work, we study the generation and propagation of surface plasmon polaritons (SPPs) in a geometrically flat insulator-metal-insulator (IMI) structure with parity-time (PT) symmetric modulation on the dielectric layers. Unidirectional SPPs are generated by PT-symmetric modulation. Moreover, magnetic field switching is obtained between two metal-dielectric interfaces. It has been noticed that the metal thickness affects the oscillation frequency of excited SPPs along the direction of propagation. Also, we report that the field at the upper interface is manipulated by solely maneuvering the permittivity of the bottom dielectric. The magnetic field distribution of the present structure is studied using COMSOL Multiphysics software. To ensure the accuracy and reliability of the simulation results, comprehensive analytical investigations have also been conducted.

Terahertz and Infrared Plasmon Polaritons in PtTe2 Type-II Dirac Topological Semimetal.

Surface plasmon polaritons (SPPs) are electromagnetic excitations existing at the interface between a metal and a dielectric. SPPs provide a promising path in nanophotonic devicesforlight manipulation at the micro and nanoscale with applications in optoelectronics, biomedicine, and energy harvesting. Recently, SPPs have been extended to unconventional materials like graphene, transparent oxides, superconductors, and topological systems characterized by linearly dispersive electronic bands. In this case, three-dimensional Dirac and Weyl semimetals offer a promising frontier for infrared (IR) and terahertz (THz) radiation tuning by topologically-protected SPPs.In this work, we investigate the THz-IR optical response, of platinum ditelluride (PtTe2) type-II Dirac topological semimetal films grown on Si substrates. We detect SPPs generated on microscale ribbon arrays of PtTe2in the far-field limit,finding an excellent agreement among measurements, theoretical model, and electromagnetic simulation data.The far-field measurements have been further supported by near-field infrared data which indicate a strong electric field enhancement due to the SPP excitation near the ribbon edges. The whole results of this paper, indicate that PtTe2ribbon array appears an idealactive layout for geometrically tunable SPPs thus inspiring a new fashion of optically tunable materials in the technologically demanding THz and IR spectrum. This article is protected by copyright. All rights reserved.

Simulation-based design of 1-D copper nanograting device for sensing application by studying electromagnetic properties on Cu/Air interface

Sensing devices has been an interesting area of study because of their immense application in practical life. In the present work, the extraordinary optical transmission (EOT) along with surface plasmon polaritons (SPPs) excitation at the metal/ dielectric interface is investigated RF-module of COMSOL Multiphysics 5.3a has been used to investigate copper (Cu) nanograting structure on the glass substrate in periodic arrangement of 1-dimensional (1D). The visible-infrared electromagnetic wavelength of 400–900 nm has been used to excite the SPPs at the interface and a light port is provided from the substrate side. The optimum EOT has been investigated at transmission spectra of 0th order. During this process thickness of the slit is fixed at 50 nm, the periodicity of the unit cell is fixed at 700 nm, and the width of the slit changed to check its effect on the EOT. Additionally, phenomena of near field investigation have also used to explore the transmission-based performance of field at thespecificboundary of copper (Cu) and airwhich confirm spectraoutcomesof transmission thorough the fabricated device. The optimum value of EOT foundwhenthe width of slit isat250 nm for the Cu/air interface.The deviceused for this purpose is modeled in COMSOL. Along the EOT the SPPs phenomena is also investigated by using present modeled device.These phenomena are observed by studying the electric and magnetic parts of the device that models the Cu/Air interface. We tested it with different slit widths ranging from 50-450 nm. The coupling efficiency and sensitivity of Cu/Air 1D device design at optimum slit width of 250 nm calculated. Such devices are increasingly applicable in bio photonics sensing of DNA structure, in vivo study of the internal structure of the body, imaging, surface chemical reaction, environmental remediation, and in various solar cell industries (plasmonic solar cell).

Enhance the detection of surface micro/nanostructures by SPPs generated from silver film covered hemi-microsphere

Surface plasmon polaritons (SPPs) are widely used for surface micro/nanostructures detection. However, because of the limitations of the common SPPs excitation conditions, it is difficult to flexibly detect surface micro/nanostructures in the air without being limited by the substrate structure. In this paper, a new SPPs excitation structure is developed. This structure is a silver film covered hemi-microsphere. SPPs could be excited on the surface of the Ag film, and induce collective oscillations of free electrons on the substrate surface to generate periodic electromagnetic waves. The periodic electromagnetic waves can enhance the electromagnetic field around the surface micro/nanostructures, which could benefit the detection of those surface micro/nanostructures. This method could work in the air, and requires less of the sample structure, but also could move above the sample to achieve a large range of detection. Simulation experiment results demonstrate that this structure has a good detection effect. The maximum enhancement achieved for nanoparticles is 113-fold. This structure holds great potential for medical detection and biosensing.

Unconventional Transverse Magneto‐Optical Kerr Effect in Cobalt Nanopillar Arrays

AbstractNovel magneto‐optical (MO) properties can be actualized through well‐designed nanostructures, greatly improving the application value of MO effects. As only p‐polarized light can generate transverse magneto‐optical Kerr effect (TMOKE) in traditional MO materials, it is quite challenging and valuable to effectuate TMOKE under s‐polarization incidence at optical frequencies. The constructed nanopillar structures in this work can realize a clear TMOKE under both s‐polarization and p‐polarization incidences, as proved by experiments and simulations. Under s‐polarized incident light with an elevation angle of 45°, electric dipole resonance (EDR) and electric quadrupole resonance (EQR) are excited, resulting in the significant enhancement of TMOKE (five orders of magnitude higher than for the planar Co film). The intensity of s‐polarized TMOKE shows an increase with the enhancing diameter and height of the nanopillar structure. The amplitude of p‐polarized TMOKE is also appreciably increased due to the excitation of surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). Moreover, the Fe and Ni nanopillars display similar reflectivity and s‐polarized TMOKE behaviors in simulations. The s‐polarized TMOKE is unexpectedly observed in ferromagnetic metals for the first time, which builds up a considerable platform for the development and application of novel MO phenomena.

Nonlinear Optical Bistability Based on Surface Plasmons with Nonlinear Dirac Semimetal Substrate

In this paper, we theoretically investigated the low-threshold and controllable optical bistability (OB) of a graphene-based Otto configuration with a nonlinear three-dimensional Dirac semimetal (3D DSM) as the substrate. The combined effect of the excitation of surface plasmon polaritons (SPPs) in graphene and the very high third-order nonlinear conductivity of the 3D DSM enabled this scheme to achieve a relatively low optical bistability threshold. At the same time, this simple multilayer structure showed the tunability of OB due to the fact that the reflectance could be modulated by regulating the Fermi energy of the 3D DSM. Furthermore, we also found that the OB hysteresis curve was closely related to the relaxation time of the 3D DSM and the thickness of the air layer. We believe that this multilayer configuration could provide a reference idea for devising a bistable device.

Electric and magnetic metal-insulator-metal metasurfaces in the mid-infrared based on Babinet’s, Lorentz’s, and Kirchhoff’s principles

Metasurfaces can extend the optical properties of conventional materials by structuring surfaces at a subwavelength scale. These artificial subwavelength surfaces mimic the physics of conventional materials and can, in principle, be designed to provide novel optical material properties. Metal-insulator-metal (MIM) antenna metasurfaces are among the most widely used as ideal absorbers and emitters. In this work, we present MIM metasurfaces in the mid-infrared that comply in the electric and magnetic forms of Babinet’s, Lorentz’s, and Kirchhoff’s principles. To verify the validity of Babinet's, Lorentz's, and Kirchhoff's MIM metasurfaces, we computed their reflection and absorption spectra as well as electric and magnetic field maps. We found that even in the presence of graphene on top of the electric and magnetic MIM metasurfaces, these principles still hold qualitatively. However, the excitation of gap surface plasmon polaritons (SPPs) and graphene SPPs fails to comply quantitatively. Additionally, we fabricated the MIM metasurfaces and used imaging Fourier transform infrared spectroscopy in the mid infrared spectrum to validate them. Finally, we explore the potentials and limits of the use of graphene as tunability material, with a tunability bandwidth up to 0.6 µm. Our findings can be applied to the development of electric and magnetic frequency selectivity metasurfaces, polarizers, coherent thermal sources, and detectors.

Smart city compatible thin film solar cell based on extraordinary transmission and metallic patch nanoantenna

An effective performance enhancement model for the thin film solar cell conjointly based on extraordinary transmission and nanoantenna is proposed and investigated. The absorber layer of the extraordinary transmission based solar cell contains a metallic thin film with periodic holes. Maximum extraordinary transmission is accomplished as the metallic film has the same refractive index on both sides. Increased light transmission causes the absorber layer to absorb more light, which increases short circuit current density and subsequently the efficiency of the thin film solar cell. The presented analysis demonstrates that adding a square nano patch on the top surface of the absorber layer can further boost the extraordinary transmission. The extraordinary transmission is increased because of the formation of cavity nanoantenna. Cavity nanoantenna increases the coupling of light into the hole due to the excitation of surface plasmons polaritons. The proposed design of solar cell exhibits around 98% absorption and the short circuit current density is increased by a factor of 3.23. The study has been carried out using finite difference time domain (FDTD) method.

Analytical calculation of beam profile and orbital angular momentum spectrum of Laguerre Gaussian beams reflected from a graphene plasmonic structure.

In this paper, Laguerre Gaussian (LG) beams with different topological charges are used for excitation of surface plasmon polaritons (SPPs) through a graphene layer inserted in the Otto-configuration. By utilizing the angular spectrum representation (ASR) and Lorenz-gauge vector potential, an explicit analytical expression is derived for the electromagnetic fields of the reflected beam. At the optimal excitation state of graphene SPPs, the reflected beam exhibits a distinctive field profile characterized by two identical crescent-shaped lobes separated by a vertical strip with null intensity. Furthermore, in the absence of external magnetic field, the orbital angular momentum (OAM) spectrum of the reflected beam at the optimal excitation of SPPs reveals the annihilation of central OAM mode and the generation of two equal OAM sidebands, regardless of the incident OAM topological charge. Furthermore, the phase distributions of electric field of the reflected beam confirm the existence of OAM sidebands in the vicinity of optimal SPPs excitation. As the system is taken away from the optimal excitation of SPPs by introduction of an external magnetic field or increasing the chemical potential or increasing the incident angle, both central and sideband modes appear in the OAM spectrum of the reflected beam. In this case, when the topological charge of the incident wave increases, the weight of central OAM mode decreases while the weight of sidebands increases. In contrast, in the presence of external magnetic field, at the optimal excitation of SPPs, both central OAM and sidebands modes exist in the reflected beam such that the weight of central modes increases with the external magnetic field. This effect is also confirmed by plotting the phase distributions of the reflected beam at different external magnetic fields and for different incident topological charges. Therefore, the manipulation of graphene plasmons characteristics leads to the control of OAM sideband generation.

Plasmonic slanted slit gratings for efficient through-substrate light-plasmon coupling and sensing

We present an experimental study of plasmonic slanted slit gratings (PSSGs) designed to achieve directional coupling between an incident light beam and surface plasmon polaritons (SPPs) propagating along the surface of the structure. We also investigate mirrored PSSG pairs interconnected by a plasmonic slab waveguide. The structures are fabricated using direct milling by a gallium focused ion beam (FIB). In a mirrored pair arrangement, the first PSSG couples a perpendicularly-incident light beam to SPPs propagating in one direction along the waveguide, while the second PSSG decouples SPPs to perpendicularly-emerging light. This configuration shows promise for sensing applications due to the high sensitivity of the excited SPPs to changes in the refractive index of the bounding medium, and the separation of the optics from the fluidics by the substrate. The design also exhibits robustness to fabrication tolerances. The optical characteristics and sensing potential are investigated theoretically and experimentally, highlighting its potential for a wide range of applications.

Ultra-broadband high-efficiency solar absorber based on Ti-GaAs-Au structure for UV to near-infrared spectral range

In this study, we propose an ultra-broadband solar absorber composed of a trapezoidal base, an outer circular ring, and four nano-cylinders. The absorber has a covered bandwidth range of 300–4000 nm and a temperature range of 373–973 K. The average absorptance within the mentioned wavelength range is over 96.52%, and the efficiency of solar energy thermal conversion is above 0.9 at 373–973 K under a solar concentration factor of 1000, with a maximum efficiency of 0.9644. Analysis of its absorption mechanism using the finite-difference time-domain method indicates that the proposed solar absorber’s outstanding absorption performance is due to the excitation of surface plasmon polaritons, localized surface plasmon resonances, and cavity resonances enhanced electromagnetic fields. This result has also been validated by the impedance matching theory. Moreover, the proposed solar absorber exhibits insensitivity to different polarization angles and maintains a high absorption effect in the range of 0°–70° incidence angle. The designed solar absorber has potential applications in areas such as seawater purification, wastewater treatment, and steam power generation systems.

Plasmonic Optical Fiber Based Continuous in-Vivo Glucose Monitoring for ICU/CCU Setup.

This paper reports a sensor architecture for continuous monitoring of biomarkers directly in the blood, especially for ICU/CCU patients requiring critical care and rapid biomarker measurement. The sensor is based on a simple optical fiber that can be inserted through a catheter into the bloodstream, wherein gold nanoparticles are attached at its far distal end as a plasmonic material for highly sensitive opto-chemical sensing of target biomolecules (glucose in our application) via the excitation of surface plasmon polaritons. For specificity, the nanoparticles are functionalized with a specific receptor enzyme that enables the localized surface plasmon resonance (LSPR)-based targeted bio-sensing. Further, a micro dialysis probe is introduced in the proposed architecture, which facilitates continuous monitoring for an extended period without fouling the sensor surface with cells and blood debris present in whole blood, leading to prolonged enhanced sensitivity and limit of detection, relative to existing state-of-the-art continuous monitoring devices that can conduct direct measurements in blood. To establish this proof-of-concept, we tested the sensor device to monitor glucose in-vivo involving an animal model, where continuous monitoring was done directly in the circulation of living rats. The sensor's sensitivity to glucose was found to be 0.0354 a.u./mg.dl-1 with a detection limit of 50.89 mg/dl.

Tamm plasmon polariton-based planar hot-electron photodetector for the near-infrared region.

Light-trapping devices have always been a topic of intense interest among researchers. One such device that has gained attention is the hot-electron photodetector with a tunable detection wavelength. Photodetectors based on plasmon nanostructures that provide excitation of surface plasmon polaritons are challenging to manufacture. To address this issue, a planar hot-electron photodetector based on a Tamm plasmon polariton localized in a metal-semiconductor-multilayer mirror structure has been proposed in this study. The parameters and materials of the structure were adjusted to ensure perfect absorption at the resonance wavelength. As a result, the photoresponsivity of the proposed device can reach 42.6 mA W-1 at 905 nm. For the first time, the photosensitivity was calculated analytically by solving the dispersion law for the Tamm plasmon polariton.

Plasma amplifiers: multiscale light-enhanced uniform SERS composite substrates for breaking through resonance limitations.

A phenomenon known as plasmon resonance constitutes a unique optical effect that can induce an enhancement in localized electromagnetic fields, resulting in a substantial increase in the electromagnetic field intensity surrounding metallic nanostructures. In this work, the coupling effect of excitation of surface plasmon polaritons and local surface plasmons in nanoparticles is deeply studied under the background of nanoparticles/one-dimension grating composite structures through grating matching. By employing finite-difference time-domain simulations as our methodological approach, we discern gratings with a periodicity of 1.5 μm support surface plasmon bound states between the gratings. Furthermore, the modulation of SPs along the vertical sidewalls of the grating due to standing wave effects exhibits oscillatory behavior with varying grating heights. Experimental results obtained from the nanoparticle/grating composite SERS substrate validate theoretical predictions, demonstrating higher enhanced Raman signals at 633 nm compared to 532 nm. Remarkably, this structure exhibits good performance, with R6G detection sensitivity down to concentrations as low as 10-10 M and mapping achieving a relative standard deviation of 7.79%, underscoring its uniformity and capability of electromagnetic field enhancement.

Вплив тонких плівок Se на ефективність збудження поверхневих плазмон-поляритонів в срібних та алюмінієвих голографічних решітках

In this paper, we study the effect of thin selenium layers up to 3 nm thick on the efficiency of excitation of surface plasmon polaritons (SPPs). The Se layers were deposited by thermal evaporation in vacuum on the surface of silver and aluminum gratings. Gratings with a groove profile close to sinusoidal and a period equal to а = 694 nm were formed on chalcogenide photoresist films using interference lithography. Then they were coated with layers of the above metals with a thickness of 80–85 nm using thermal evaporation. Registration of SPP excitation on the gratings was carried out by measuring the angular dependences of the intensity of specularly reflected or diffracted p-polarized He-Ne laser radiation on a stand mounted on the basis of a G5M goniometer and a Fedorov table. An atomic force microscope was used to determine the shape of the groove profile and the depth of the grating relief. It has been found that for silver gratings with a relief modulation depth h/a less than the optimal value (which ensures maximum plasmon absorption, i.e., the maximum efficiency of SPP excitation), selenium deposition causes significant degradation of the plasmon resonance: a decrease in the depth of the minimum of the total reflection Rpt (i.e., a decrease in the efficiency of plasmon absorption), a shift of the Rpt minimum towards larger angles, and its widering. For silver gratings with h/a greater than the optimal value, a similar shift and widering of the plasmon resonance is also observed. However, at the same time, a significant deepening of the Rpt minimum is recorded, that is, an increase in the efficiency of SPP excitation. Such changes in the plasmon characteristics also appear on aluminum gratings, however, in this case the effect of the selenium layers is weaker by an order of magnitude. The obtained results allow us to propose a method of correcting the plasmonic characteristics of silver gratings in which the value of h/a is higher than optimal.

High‐Efficiency Pancharatnam–Berry Metasurface‐Based Surface Plasma Coupler

To excite surface plasmon polaritons (SPPs) in an ultrathin way, metasurface‐based SPP couplers are widely used for converting propagating waves into driven waves bounded on their surfaces. Among them, the Pancharatnam–Berry (PB) metasurface coupler has a strong ability to control spin‐polarized waves, but is still limited by its coupling efficiency. Herein, a PB metasurface‐based SPP coupler that can support efficient circular‐polarization conversion with both the transverse magnetic and transverse electric modes of the SPP is proposed. The coupler is composed of an upper transmissive PB gradient metasurface and a lower eigenmode board to transform a circularly polarized plane wave into left‐handed circularly polarized and right‐handed circularly polarized surface waves that propagate in opposite directions. In the experimental results, it is indicated that the directionality factor of the tested SPP coupler is 28.6. The proposed PB metasurface coupler may pave the way for future integrated optical devices with high efficiency and excellent polarization‐split properties.

Femtosecond laser induced periodic surface structures on crystals: Formation, evolution and application

In the research field of laser induced periodic surface structures (LIPSSs), the ones located at the superficial surface of the solid materials (s-LIPSSs) induced by femtosecond laser have been widely investigated. It is noticed that, the formation of s-LIPSSs is limited to a relatively narrow parameter window and, as the parameters are tailored, such structures would evolve into novel topographies which possess laser-ablated micro-grooves with LIPSSs being deeply located at the groove-bottoms (d-LIPSSs). In this work, both s-LIPSSs and d-LIPSSs are produced on the surface of Nd:LGGG crystal by using femtosecond laser irradiation. Experimental investigations and numerical modeling convince the crucial role of surface plasmon polariton excitation in the formation of both structures. The evolution of surface topographies and the dependence of LIPSSs-periods on the fabricating parameters can be mainly ascribed to the feedback mechanisms of s-LIPSSs and laser-induced micro-grooves. Furthermore, based on the d-LIPSSs, a novel approach is proposed to fabricate 2-dimensional surface with orthogonal dual-periods. Such structure shows enhanced polarization-sensitive antireflectivity within long wavelength range and the ability for NIR detection, which is superior to the traditional surface structure composed of s-LIPSSs.

Screening and optimization of metal-insulator-metal selective emitter in thermophotovoltaic system

In thermophotovoltaic (TPV) systems, it is crucial that the selective emitters can tailor emission spectrum to match the bandgap of photovoltaic (PV) cells and largely enhance the system efficiency. In this work, a metamaterial emitter based on the metal-insulator-metal (MIM) structure is proposed to obtain the high energy conversion efficiencies. The geometric parameters of MIM emitter have been investigated to obtain an excellent radiation spectrum of emitter composed of W and HfO2. The excellent emission performance of MIM emitter is attributed to the excitation of surface plasmon polariton (SPP) and cavity resonance, and the structure of MIM emitter is insensitive for different polarization modes. The 21 material combinations of MIM emitters have been screened to obtain the optimal emitter matching GaSb and InGaAsSb cells. This work identifies the crucial role of structure and materials into the emitter of a TPV system. In the evaluation of MIM emitter and TPV System, when the operating temperature of emitter increases from 1400[Formula: see text]K to 2000[Formula: see text]K, the system efficiency of optimal W/HfO2/W MIM emitter increases from 20.26% to 30.41%, while the output electric power increases from 3.59[Formula: see text]kW/m2 to 42.48[Formula: see text]kW/m2. The phenomenon indicates that the MIM emitter with the optimal material combinations and geometric parameters can significantly improve the matching degree with GaSb and InGaAsSb cells. Our results will be helpful to expand the optimization scope of metamaterial emitters in TPV systems.

Near-Field Observation of the Photonic Spin Hall Effect.

The photonic spin Hall effect, referring to the spatial separation of photons with opposite spins due to spin-orbit interactions, has enabled potential for various spin-sensitive applications and devices. Here, using scattering-type near-field scanning optical microscopy, we observe spin-orbit interactions introduced by a subwavelength semiring antenna integrated in a plasmonic circuit. Clear evidence of unidirectional excitation of surface plasmon polaritons is obtained by direct comparison of the amplitude- and phase-resolved near-field maps of the plasmonic nanocircuit under excitation with photons of opposite spin states coupled to a plasmonic nanoantenna. We present details of the antenna design and experimental methods to investigate the spatial variation of complex electromagnetic fields in a spin-sensitive plasmonic circuit. The reported findings offer valuable insights into the generation, characterization, and application of the photonic spin Hall effect in photonic integrated circuits for future and emerging spin-selective nanophotonic systems.

Near-field radiative heat transfer between nanoporous GaN films

Photon tunneling effects give rise to surface waves, amplifying radiative heat transfer in the near-field regime. Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer, leading to a substantial enhancement of near-field radiative heat transfer (NFRHT). Being a direct bandgap semiconductor, GaN has high thermal conductivity and stable resistance at high temperatures, and holds significant potential for applications in optoelectronic devices. Indeed, study of NFRHT between nanoporous GaN films is currently lacking, hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT. In this work, we delve into the NFRHT of GaN nanoporous films in terms of gap distance, GaN film thickness and the vacuum filling ratio. The results demonstrate a 27.2% increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5. Moreover, the spectral heat flux exhibits redshift with increase in the vacuum filling ratio. To be more precise, the peak of spectral heat flux moves from ω = 1.31 × 1014 rad⋅s−1 to ω = 1.23 × 1014 rad⋅s−1 when the vacuum filling ratio changes from f = 0.1 to f = 0.5; this can be attributed to the excitation of surface phonon polaritons. The introduction of graphene into these configurations can highly enhance the NFRHT, and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio, which can be explained by the excitation of surface plasmon polaritons. These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control, management and thermal modulation.