Surface Electromagnetic Waves Research Articles

Coherence effects in LIPSS formation on silicon wafers upon picosecond laser pulse irradiations

Abstract Using different laser irradiation patterns to modify silicon surface, it has been demonstrated that, at rather small overlapping between irradiation spots, highly regular laser-induced periodic surface structures (LIPSS) can be produced already starting from the second laser pulse, provided that polarization direction coincides with the scanning direction. If the laser irradiation spot is shifted from the previous one perpendicular to light polarization, LIPSS are not formed even after many pulses. This coherence effect is explained by a three-wave interference, surface electromagnetic waves (SEWs) generated within the irradiated spot, SEWs scattered from the crater edge formed by the previous laser pulse, and the incoming laser pulse, providing conditions for amplification of the periodic light-absorption pattern. To study possible consequences of SEW scattering from the laser-modified regions, where the refractive index can change due to material melting, amorphization, and the residual stress formed by previous laser pulses, hydrodynamic modelling and simulations have been performed within the melting regime. The simulations show that stress and vertical displacement could be amplified upon laser scanning. Both mechanisms, three-wave interference and stress accumulation, could enable an additional degree of controlling surface structuring.

Discovery of Electromagnetic Surface Waves at the Interface between Perfect Electric Conductor and Perfect Magnetic Conductor Parallel-Plate Waveguides.

We propose new electromagnetic surface waves at the interface formed by connecting perfect electric conductor (PEC) and perfect magnetic conductor (PMC) parallel plate waveguides containing materials with positive permittivities and permeabilities. This challenges the conventional understanding that surface waves require materials with negative permittivity or permeability. Theoretical mode analysis and numerical simulations have confirmed the existence of surface waves at the PEC-PMC interface. Additionally, a simulated prism coupling experiment validated the excitation of the surface watpdel 1ve at the PEC-PMC interface. The resonant response of the localized surface waves on the enclosed PEC-PMC surface of a cylinder also closely resembles that of a Drude cylinder. Our finding broadens the understanding of the conditions for generating electromagnetic surface waves and deepens our comprehension of electromagnetic phenomena.

Electromagnetic Surface Waves in a Relativistic Magnetized Plasma Propagating in a Cylindrical Column

Dispersion relations of electromagnetic surface waves in a magnetized relativistic plasma propagating in a cylindrical column surrounded by vacuum are derived by means of the relativistic fluid equations. The zero order relativistic beam is assumed to stream along the direction of the axial magnetic field. The coupled equations of the E- and B-wave modes are solved analytically in terms of the cylindrical coordinates in weak or intermediate values of the magnetic field in which the cyclotron frequency is much smaller than the relativistic Doppler-shifted frequency. The entangled field components of the E- and B-waves are decoupled by assuming that the flow is incompressible. The surface wave dispersion relations of the E- and B-wave modes show a strong similarity and symmetry. The static magnetic field splits the E- and B-waves, thus doubling the modes in unmagnetized plasma. By taking the radius of the cylinder infinite, the dispersion relations in a semi-infinite plasma are derived.

Effect of surface electromagnetic wave treatment on the refractive properties of thin films based on indium tin oxides with laser-deposited single-walled carbon nanotubes

Effect of surface electromagnetic wave treatment on the refractive properties of thin films based on indium tin oxides with laser-deposited single-walled carbon nanotubes

In-Situ Surface Modification of Nickel Mesh for Superior Electromagnetic Interference Shielding

Metal mesh, with its inherent conductivity, transparency, and flexibility, has proven to be an exceptional choice for high-performance reflection-dominated electromagnetic interference (EMI) shielding materials, due to its multifunctionality and wide applicability. However, the development of metal-based absorption-enhanced EMI shielding materials characterized by high absorption and low reflection is crucial but remains challenging. Herein, we introduce a novel surface modification strategy for nickel mesh (NM) aimed at augmenting its surface electromagnetic wave absorption through electrochemical surface microstructure alteration and subsequent wet chemical sulphuration. This approach leverages the multiple reflections within the microporous structure and the impedance matching enhancement provided by the magnetic sulfided nickel layer, resulting in the sulphur-treated porous NM (Ni3S2-PNM) achieving an outstanding average EMI SE of 59.6 dB across a broad frequency range of 4 to 40 GHz. The surface electromagnetic wave absorption rate of Ni3S2-PNM has increased from under 1% for unmodified NM to over 60%, significantly reducing the re-reflection of electromagnetic waves back into free space (the average SER value decreases from about 20 dB to 2.2 dB). Characterized by its simplicity and cost-effectiveness, this in-situ surface modification method on bulk industrial-grade NM, enhancing electromagnetic shielding, presents a promising avenue for wider application in electromagnetic protection.

Electromagnetic surface waves guided by the interface of a metal and a tightly interlaced matched ambidextrous bilayer

The existence and characteristics of electromagnetic surface waves (ESWs) whose propagation is guided by the planar interface of metal and a tightly interlaced matched ambidextrous bilayer (TIMAB) were theoretically investigated, a TIMAB being a periodic unidirectionally nonhomogeneous material whose unit cell consists of one period each of two structurally chiral materials that are identical except in structural handedness. Thus, the structural handedness flips in the center of the unit cell. A canonical boundary-value problem was formulated and a dispersion equation was solved, the ESWs being classified as surface-plasmon-polariton (SPP) waves. Flipping the structural handedness once in the unit cell can greatly enhance the number of possible SPP waves, one or more of which may be superluminal.

Dyakonov surface waves in a thin interfacial waveguide formed by negatively anisotropic dielectrics.

Dyakonov surface waves (DSWs) are electromagnetic surface waves that exist at the interface of two dissimilar materials, with at least one material being anisotropic. Although there are various types of these waves, they all exist in anisotropic materials with positive anisotropy. The requirement for positive anisotropy limits the choice of materials that can support these waves. In this study, we present a type of Dyakonov surface wave that occurs at the interface of negatively anisotropic materials. Specifically, we demonstrate their existence in a system consisting of two negatively anisotropic slabs confined between two perfect electric conductor (PEC) walls. By assuming a small distance between the walls, we derive analytical expressions for the propagation constant, penetration depth, and field distribution of these surface waves. We numerically demonstrate that these surface waves can also exist in structures beyond the approximations used to develop the theoretical framework. The existence of Dyakonov surface waves in negative crystals broadens the range of materials suitable for their practical implementation.

Experimental Observation of Surface Wave States at the Gold–Silver Interface

We demonstrate that a gradual interface between gold and silver supports the propagation of a novel kind of surface electromagnetic wave, which is different from the more well-known surface plasmon polaritons. The existence of such surface waves leads to a paradoxical situation in which a continuous metal barrier which does not have any pinholes may exhibit considerably increased light transmission if the barrier is made of two different metals. A spectroscopic study of this effect is reported.

Transmission of High-Definition Video Signals and Detection of the Objects Underwater Using Surface Electromagnetic Waves

Transmission of High-Definition Video Signals and Detection of the Objects Underwater Using Surface Electromagnetic Waves

Tunable properties of graphene loaded waveguide surrounded by magnetic materials

Theoretically analysis has been accomplished for the propagating electromagnetic surface waves (EMSWs) at planar ferrite-graphene-ferrite waveguide structure. The characteristics curves are analyzed for the normalized phase and attenuation phase constant against the operating frequency. The impact of different parameters of ferrite and graphene are observed on the normalize phase and attenuation phase constant. In response to these parameters the structured waveguide exhibits the convenient propagation of electromagnetic surface waves with minimal propagation loss in the terahertz frequency region. The proposed waveguide avails position in nanophotonic devices, terahertz filters, highly integrated terahertz devices and communication systems.

Relations between group, energy, and phase velocities of surface electromagnetic waves in half-infinite bianisotropic homogeneous media

Relations between group, energy, and phase velocities of surface electromagnetic waves in half-infinite bianisotropic homogeneous media

Surface wave propagation along a narrow transition layer in a slab Voigt geometry

The dispersion properties of electromagnetic surface waves, which propagate along a slab narrow transition layer separating two magnetoactive plasma uniform half spaces, are studied. Voigt geometry is considered, in which the waves propagate perpendicularly to an external uniform static magnetic field, which in turn is parallel to the interfaces between the plasmas and the transition layer. Electromagnetic power absorption within local resonances inside the transition layer is out of scope of the study. The influence of the plasma particle density profile smoothness on the surface wave dispersion properties is emphasized.

Temperature-Dependent Electromagnetic Surface Wave Supported by Graphene-Loaded Indium Antimonide Planar Structure

In this study, the propagation characteristics of EM surface waves supported by the graphene-coated indium antimonide (InSb) planar waveguide have been investigated theoretically and numerically. The modeling of graphene has been performed by use of Kubo formalism whereas the relative permittivity of indium antimonide has been calculated using Drude’s model. The results for transverse electric (TE) and transverse magnetic (TM) polarized surface waves have been computed analytically and numerically. The major challenge is to model the atomically thick graphene sheet over the InSb grounded slab. To get the temperature-dependent characteristic equation for the electromagnetic surface waves, the surface current boundary conditions’ approach has been employed. The numerical results have been computed for both the TE and TM polarization states and reported that the TE does not support the propagation of surface waves. The dispersion relation, effective mode index, phase speed, propagation length, and field profile have been computed in Mathematica under TM polarization. The graphene and indium antimonide have been found active for low and high Terahertz regions, respectively. As temperature increases, the plasma frequency of the InSb increases due to this reason with the increase of temperature and the resonance frequency, leading to a shift in the dispersion curve. Moreover, with the increase of temperature, the effective wave number of transverse magnetic polarized surface waves also increases. Resultantly, the confinement of such surface waves supported by graphene-loaded InSb increases. It is shown that with the variation of temperature of indium antimonide, the surface waves propagating across the interface can be tuned in the Terahertz region and can be exploited for thermo-optical sensing, near-field communications waveguides, and graphene-based temperature sensor designing.

Comparative Analysis of Ethanol Gas Sensors Based on Bloch Surface Wave and Surface Plasmon Resonance

Ethanol plays a crucial role in modern industrial processes and consumer products. Despite its presence in human activity, short and long-term exposure to gaseous ethanol poses risks to health conditions and material damage, making the control of its concentration in the atmosphere of high importance. Ethanol optical sensors based on electromagnetic surface waves (ESWs) are presented, with sensitivity to ethanol vapours being achieved by the inclusion of ethanol-adsorptive zinc oxide (ZnO) layers. The changes in optical properties modulate the resonant conditions of ESWs, enabling the tracking of ethanol concentration in the atmosphere. A comprehensive comparative study of sensor performance is carried out between surface plasmon resonance (SPR) and Bloch surface wave (BSW) based sensors. Sensor efficiency is simulated by transfer matrix method towards optimized figures of merit (FoM). Preliminary results validate ethanol sensitivity of BSW based sensor, showcasing a possible alternative to electromagnetic and plasmonic sensors.

All-optically controlled holographic plasmonic vortex array for multiple metallic particles manipulation

Due to the sub-diffraction-limited size and giant field enhancement, plasmonic tweezers have a natural advantage in trapping metallic particles. However, the strict excitation condition makes it difficult to generate an arbitrary plasmonic field in a controllable manner, thus narrowing its practical applications. Here, we propose an all-optical plasmonic field shaping method based on a digital holographic algorithm and generate plasmonic vortex arrays with controllable spot numbers, spatial location, and topological charge. Our experimental results demonstrate that multiple gold particles can be stably trapped and synchronously rotated in the vortex arrays, and the particles’ kinestate can be dynamically switched. The proposed holographic plasmonic vortex tweezers are suitable for a broadband particle trapping, and this method can be generalized to other surface electromagnetic waves like Bloch surface wave.

Electromagnetic signal propagation through lossy media via surface electromagnetic waves.

A theory of surface electromagnetic waves in gradient media exhibiting arbitrary surface gradients of dielectric permittivity and magnetic permeability has been developed. Novel low-loss propagating surface wave solutions have been found in the gradient media in which both dielectric permittivity and magnetic permeability are dominated by their imaginary parts. Several examples of gradient geometries in which the surface wave problem may be solved analytically have been found. Examples of practically useful surface wave geometries spanning from radio communication underwater to UV nanophotonics have been demonstrated.

Surface Electromagnetic TE-Waves Total Internal Reflection

We have considered the refraction of surface electromagnetic waves (SEW) at the heterogeneous metasurface. The considered structure consists of three regions: mu-negative metamaterial, ordinary magnetic, and vacuum. The boundaries between considered media are planar. A phenomenological approach was used; media were assumed to be lossless and isotropic. In this paper, we show the possibility of total internal reflection effect for SEW of TE-polarization that can propagate along such heterogeneous metasurface. The value of the angle of total internal reflection decreases for higher frequency waves from the interval under consideration. The presented result may help design both research and industry complex systems.

Terahertz Generation through Coherent Excitation of Slow Surface Waves in an Array of Carbon Nanotubes

In this paper, we present a scheme for generating terahertz (THz) radiation using an array of parallel double-walled carbon nanotubes (DWCNTs) subjected to a direct current (DC). The longitudinal surface plasmon polaritons (SPPs) in the DWCNTs are coherently excited by two near-infrared laser beams with slightly different frequencies. Through numerical methods, we investigate the spectral characteristics of the SPPs in the presence of a DC current in the nanotubes. We identify high-quality plasmonic modes with a slowdown factor exceeding 300 in the terahertz frequency region. The amplification of these slow SPP modes is facilitated by the DC current in the DWCNTs, fulfilling a synchronism condition. This condition ensures that the phase velocity of the SPPs is closely matched to the drift velocity of the charge carriers, allowing for an efficient energy exchange between the current and the surface electromagnetic wave. The high-frequency currents on the nanotube walls in the DWCNT array enable the emission of THz radiation into the far field, owing to an antenna effect.

Resonant amplification of slow surface plasmon polaritons in a DC current pumped semiconductor/graphene waveguide with a groove defect

We propose the principle of a planar surface plasmon polariton amplifier composed of a complex waveguide structure based on a semiconductor thin film separated from a dielectric substrate by a graphene monolayer. The amplification of surface plasmon polaritons in that waveguide in the terahertz regime is driven by a direct current in the graphene layer under a synchronism condition that allows an efficient energy exchange from the collective flux of charge carriers in graphene and the surface electromagnetic wave in the semiconductor film. Positive feedback required for resonant amplification is achieved through surface plasmon polariton reflections at the edges of the active waveguide, one of which is formed by a local thickness defect (a groove) at the upper surface of the semiconductor film that also provides an exit channel for the energy of the amplified surface wave to be transferred to an adjacent passive thin film semiconductor waveguide. We determine the conditions required for the resonant amplification of surface plasmon polaritons in that complex structure, which are essentially governed by the geometry of the groove as well as by the characteristic parameters of the active and passive waveguides.

Thermally tunable electromagnetic surface waves supported by graphene loaded indium antimonide (InSb) interface

The thermal agitation plays a vital role in tunability of optoelectronic, structural and chemical characteristics of the temperature sensitive materials. Graphene enables the THz optics, due to its unprecedent controlling characteristics over the traditional materials. The influence of temperature on the monolayer graphene is very negligible due to its low free charge carrier density, to enhance the thermal sensitivity of graphene, the graphene loaded temperature sensitive material interface has been proposed. A theoretical analysis has been carried out on temperature dependent propagation characteristics of electromagnetic surface waves supported by the graphene loaded semi-infinite indium antimonide (InSb). The InSb has been taken as temperature sensitive material. The Drude model has been used for the modeling of InSb in the THz region while the modeling of the graphene has been done by random phase approximation-based Kubo’s formulism. To realize the graphene loaded indium antimonide interface, the impedance boundary conditions (IBCs) have been employed. The numerical analysis has been conducted to analyze the influence of temperature on the characteristics of electromagnetic surface waves i.e., dispersion curve, effective mode index (Neff), penetration depth (δ), propagation length (Lp), phase speed (Vp) and field profile, propagating along the graphene loaded InSb. In all the numerical results, the temperature variation has been considered from 200 to 350 K. It has been concluded that the graphene–InSb interface provides more temperature assisted tunability to the interfacial surface modes, commonly known as surface waves, as compared to monolayer graphene. Further, the graphene parameters can play a vital role in the dynamical tuning of electromagnetic surface waves in THz to IR frequency range. The numerically computed results have potential applications in designing of thermo-optical waveguides, temperature assisted communication devices, thermo-optical sensors and near field thermal imaging platforms.