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Plasmonics || Introductory Chapter: Plasmonics
摘要： The optical interaction with nanostructures is studied by the field of plasmonics. Recently, the potential of subwavelength confinement and the enhancement of optical fields close to the appropriately designed nanoscale objects have opened a gateway to extensive investigations of plasmonic optical phenomena. Consequently, the outstanding field of plasmonics has spread over different disciplines, providing the wide avenues for the promising applications in materials science, biology, and engineering. Furthermore, the field of metamaterials has been enriched and enhanced by the plasmonic optics, for example, metasurfaces. The former concept is based on the collective electromagnetic behavior of many subwavelength inclusions and building blocks as “meta-atoms.” Doing so, novel tunable composite materials, i.e., near-zero material parameters, and extreme-value material parameters, characterized by unconventional bulk and surface properties, have been proposed and applied. Surface waves open a gateway to a wide spectrum of physical phenomena providing a fertile ground for a number of applications [1–3]. The discovery of metamaterials with tunable electric and magnetic features [4] has allowed for a rich phenomenon, i.e., expansion of the wide spectrum of structures capable of supporting surface waves. Surface plasmon polaritons (SPPs) are electromagnetic excitations occurring at the interface between a conductor and dielectric. These are evanescently confined in the perpendicular direction [5–8]. It is possible to imitate the properties of confined SPPs by geometrical-induced SPPs, named as spoof SPPs. The proposed phenomenon may take place at lower frequencies. It might be concluded that surface structure may open a gateway to spoof surface plasmons. The former serves as a perfect prototype for structured surfaces [9]. Thus, metasurfaces, a class of planar metamaterials possessing the outstanding functionality, i.e., capabilities to mold light flow, have recently attracted intensive attention. The main goal of the metasurfaces is to achieve the anticipated phase profile by designing subwavelength structures at the interface between two ordinary materials. Abilities to fully engineer the properties of the propagating waves are gained thanks to the rationally designed phase. It should be mentioned that anomalous reflection and refraction have been verified in the infrared range. Metasurface-based optical devices, such as vortex plates, waveplates, and ultra-thin focusing lenses have also been proposed for various types of incident light, i.e., linearly polarized light or vertex beams. Now is the time that the fundamental research in the field is giving rise to the first promising applications for industry. For centuries, the control of optical properties has been limited to altering material compositions, relying on light propagation through naturally occurring materials to impart phase shifts and tailor the desired wavefronts. The introduction of metamaterials allows control over optical wavefronts to deviate from the usual propagation methods and rely instead on its carefully engineered internal structure. This was first theorized 20 years ago by Pendry et al. [10], and since then, the development in the field of artificially designed materials has only accelerated. Metamaterials offer an extensive range of novel electromagnetic phenomena, which do not occur in natural materials, but whose existence is not restricted by physical laws. These artificially created “materials” are made up of a series of composite unit elements, which although are a few orders of magnitude larger than the molecular unit cells of regular materials. This allows the metamaterials to provide descriptions of its interactions with electromagnetic waves in terms of its effective “material” parameters. Metamaterials can, therefore, still be viewed as a homogenous material at their desired operational wavelengths, typically within the optical regime. With careful structuring of the elements within the metamaterial, unusual material properties such as a negative refractive index can be achieved. The refractive index η of a material is governed by its macroscopic electromagnetic permittivity e and permeability μ, where η=√eμ. The development of such negative index material could lead to novel applications especially within the optical regime, such as creating the perfect lens, which images beyond the diffraction limit, or an optical cloaking device. The initial realization of a negative refractive index metamaterial uses a pattern of metallic wires and split-ring resonators to form its unit cells, which have been experimentally demonstrated in the microwave regime and later at optical wavelengths as the elemental array is reduced into the nanoscale. Bulk metamaterials, however, are usually susceptible to high losses and strong dispersive effects due to the resonant responses of metallic structures used. Additionally, the complex structures required in a 3D metamaterial is challenging to build using the existing micro- and nanofabrication methods. Thus, recent studies have been focusing on the development of 2D metamaterials, or metasurfaces. These planar materials allow for the combined advantages of the ability to engineer electromagnetic responses with low losses associated with thin layer structures. The introduction of surfaces with subwavelength thicknesses results in minimal propagation phase; this shifts the focus from developing materials with negative permittivity and permeability to engineering surface structures to adjust surface reflection and transmissions. This is made possible by exploiting abrupt phase jumps and polarization changes from scattering effects, which can be realized and subsequently fine-tuned through designing spatially varying phase responses over the metasurface, through using either metallic or dielectric surface structures. In solid state physics, materials can be classified according to their electronic band structure. While metals have overlapping conduction and valence bands, which allows the free movement of electrons through the material, dielectric insulators have a large bandgap between the two. Both types of materials are still able to interact with incident electromagnetic fields, although through different physical methods and result in light scattering effects. Thus, both materials have, therefore, been employed in the realization of the vast potential of metasurfaces.
关键词： plasmonics,surface plasmon polaritons,spoof surface plasmons,metasurfaces,metamaterials,subwavelength confinement,optical fields
更新于2025-09-11 14:15:04
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Ultrafast transport and relaxation of hot plasmonic electrons in metal-dielectric heterostructures
摘要： Owing to the ultrashort timescales of ballistic electron transport, relaxation dynamics of hot nonequilibrium electrons is conventionally considered local. Utilizing propagating surface plasmon-polaritons (SPs) in metal-dielectric heterostructures, we demonstrate that both local (relaxation) and nonlocal (transport) hot electron dynamics contribute to the transient optical response. The data obtained in two distinct series of pump-probe experiments demonstrate a strong increase in both nonthermal electron generation ef?ciency and nonlocal relaxation timescales at the SP resonance. We develop a simple kinetic model incorporating a SP excitation, where both local and nonlocal electron relaxation in metals are included, and analyze nonequilibrium electron dynamics in its entirety in the case of collective electronic excitations. Our results elucidate the role of SPs in nonequilibrium electron dynamics and demonstrate rich perspectives of ultrafast plasmonics for tailoring spatiotemporal distribution of hot electrons in metallic nanostructures.
关键词： metal-dielectric heterostructures,hot plasmonic electrons,surface plasmon-polaritons,nonequilibrium electron dynamics,ultrafast transport
更新于2025-09-11 14:15:04
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Asymmetric Long-Range Surface Plasmon Polariton Waveguides for Sensing Applications
摘要： A plasmonic sensing device based on an asymmetric long-range surface plasmon polaritons waveguide is proposed and investigated. The sensing structure consists of a microchamber and a gold strip with a cover layer, which is located on a dielectric supported by a silicon substrate. The optical and sensing properties of the device were studied using a ?nite element method. The sensitivity of the designed structure approaches 7.74 W/RIU for optimal sensing length and the limit of detection is 5.17 × 10?7 RIU. The proposed device is appropriate for a wide range of sensing applications, in ?elds that include biochemistry, environmental science, food safety, and medicine.
关键词： plasmonic waveguide,surface plasmon polaritons,Sensors
更新于2025-09-11 14:15:04
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Influence of surface plasmon polaritons on laser energy absorption and structuring of surfaces
摘要： The accurate calculation of laser energy absorption during femto- or picosecond laser pulse experiments is very important for the description of the formation of periodic surface structures. On a rough material surface, a crack or a step edge, ultrashort laser pulses can excite surface plasmon polaritons (SPP), i.e. surface plasmons coupled to a laser-electromagnetic wave. The interference of such plasmon wave and the incoming pulse leads to a periodic modulation of the deposited laser energy on the surface of the sample. In the present work, within the frames of a Two Temperature Model we propose the analytical form of the source term, which takes into account SPP excited at a step edge of a dielectric-metal interface upon irradiation of an ultrashort laser pulse at normal incidence. The influence of the laser pulse parameters on energy absorption is quantified for the example of gold. This result can be used for nanophotonic applications and for the theoretical investigation of the evolution of electronic and lattice temperatures and, therefore, of the formation of surfaces with predestined properties under controlled conditions.
关键词： Laser energy absorption,Surface plasmon polaritons,Plasmonics,LIPSS,Ultrashort laser pulses
更新于2025-09-11 14:15:04
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Photonic crystal for graphene plasmons
摘要： Photonic crystals are commonly implemented in media with periodically varying optical properties. Photonic crystals enable exquisite control of light propagation in integrated optical circuits, and also emulate advanced physical concepts. However, common photonic crystals are un?t for in-operando on/off controls. We overcome this limitation and demonstrate a broadly tunable two-dimensional photonic crystal for surface plasmon polaritons. Our platform consists of a continuous graphene monolayer integrated in a back-gated platform with nano-structured gate insulators. Infrared nano-imaging reveals the formation of a photonic bandgap and strong modulation of the local plasmonic density of states that can be turned on/off or gradually tuned by the applied gate voltage. We also implement an arti?cial domain wall which supports highly con?ned one-dimensional plasmonic modes. Our electrostatically-tunable photonic crystals are derived from standard metal oxide semiconductor ?eld effect transistor technology and pave a way for practical on-chip light manipulation.
关键词： graphene plasmons,tunable,infrared nano-imaging,Photonic crystal,surface plasmon polaritons
更新于2025-09-11 14:15:04
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Tunable enhanced sensing of ferrite film using meander-shaped spoof surface plasmon polariton waveguide
摘要： In this letter, the magnetic field enhancement characteristics of the spoof surface plasmon polaritons (SSPPs) is utilized to enhance the sensing of thin ferrite film. The operating sensing frequency can be tuned by adjusting the bias static magnetic field. For demonstration, a magnetic yttrium iron garnet film (i.e., YIG) with small thickness of 2 μm over a simple SSPP-based sensing structure is designed, fabricated and measured, showing improvement of higher than 20 dB to the absorption (i.e., sensing ability). The proposed method has significant potentials in the application of plasmonic integrated devices using thin ferrite materials.
关键词： sensing,magnetic field enhancement,spoof surface plasmon polaritons,ferrite film,SSPPs
更新于2025-09-11 14:15:04
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Tunable plasmonically induced reflection in HRR-coupled MIM waveguide structure
摘要： In this paper, a surface plasmon optical waveguide filter with half-ring resonator (HRR) based on the metal-insulator-metal (MIM) structure was designed and numerically simulated. The results show that the transmission characteristics of the structure tuned dynamically by altering the geometrical parameters. In addition, by tuning the refractive index of the filling material in the resonator, the designed waveguide structure realized a nanoscale refractive index sensor (753nm/RIU of sensitivity). Moreover, double plasmonic induced reflection (PIR) window was also achieved by adding another rectangular resonator. The as-designed structure also offers a potential method for optoelectronic devices.
关键词： EIT-like,Surface plasmon polaritons,MIM,PIR,Waveguide resonator structure
更新于2025-09-11 14:15:04
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Light absorption enhancement of plasmonic based photo-detector with double nanograting structure
摘要： This era of high speed photonic systems demands photo detectors to have large bandwidth, gain and improved light enhancement competence. Amongst the different light absorption enhancement methods being researched by the investigators, plasmonic has acquired increased attention in the last decades. Although single layer plasmonic supported metal semiconductor metal photo detector has been explored for higher light absorption efficiency, but exploration for double layer structure is lacking in literature. This paper presents performance of plasmonic based photodetector with double layer of nanogratings optimized at wavelength of 1.4 μm for night vision applications. Proposed design of plasmonic supported photodetector with double nanograting reports quenching factor of 92.14% and provides highest light enhancement with subwavelength aperture height of 60 nm. This can be credited to fact that both top and bottom layer of grating contributes to light trapping.
关键词： Surface plasmon polaritons (SPPs),Nanogratings,Nanomaterials,Plasmonics,Subwavelength aperture
更新于2025-09-11 14:15:04
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Leaky Wave Antenna Based on Periodically Truncated SSPP Waveguide
摘要： The guided waveguide structures based on surface plasmons can be used to miniaturize microwave devices. By simply introducing a series of periodic truncation slits in the SSPP (spoof surface plasmon polariton) waveguide, three frequency regions, namely radiating spatial wave region, guiding SSPP mode region, and the cut-off region, are formed. In the frequency region of radiation, the SSPP mode can be transitioned to spatial wave. Consequently, double-port leaky wave antenna based on SSPP waveguide is realized with beam sweep function. Furthermore, a single-port antenna is demonstrated by symmetrical halving of the dual-port antenna. The half-sized single-port antenna exhibits beam steering capability and improved directivity. The proposed SSPP leakage antenna can be applied to the fifth-generation (5G) mobile communication systems.
关键词： Spoof surface plasmon polaritons,Dual-port antenna,Leaky wave antenna,Single-port antenna
更新于2025-09-11 14:15:04
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Programmable Hybrid Circuit Based on Reconfigurable SPP and Spatial Waveguide Modes
摘要： A programmable hybrid circuit is proposed, which is composed of two reconfigurable spoof surface plasmon polariton (SPP) waveguides loaded with varactor diodes and a substrate integrated waveguide (SIW). By manipulating their dispersion behaviors, the band-pass effect is achieved in the hybrid circuit, in which the upper and lower cutoff frequencies are determined by the SPP waveguide and SIW, respectively. When two SPP waveguides are configured to have the same cutoff frequency that is higher than the SIW’s cutoff, the proposed circuit can realize a power division; when one SPP waveguide is reconfigured to reject the waves from SIW, this circuit will be a band-pass filter. As a typical application, a logic “OR” gate with 2-bit coding is designed by programming the bias voltages applied to the varactor diodes loaded on the unit structures of the SPP waveguides. All functions are demonstrated by measurement results that agree with numerical simulations very well. The work provides more potential applications in multifunctional integrated circuits and digital communication systems.
关键词： substrate integrated waveguide,microwave devices,spoof surface plasmon polaritons,programmable controls
更新于2025-09-11 14:15:04