五层对称人工超常材料结构的表面等离子体激元

研究了由左手材料、负介电材料、常规介电材料所构成的几种五层对称结构表面等离子体激元的特性.讨论了表面等离子体激元的存在区域、色散关系、以及p和s偏振的表面色散曲线枝,发现表面模的性质强烈依赖于系统的组成材料及其组合方式|层数越多,表面色散曲线枝也越多,处在频率通带的表面极化模态也越多|在五层结构中有p和s两种偏振的表面等离子体激元,在共振时,可导致p波和s波强透射.此外,通过使用衰减全反射方法,探讨了激发并观察表面等离子体激元的可能性.     

Surface-plasmon-polariton waves guided by the uniformly moving planar interface of a metal film and dielectric slab

We explored the effects of relative motion on the excitation of surface-plasmon-polariton (SPP) waves guided by the planar interface of a metal film and a dielectric slab, both materials being isotropic and homogeneous. Electromagnetic phasors in moving and non-moving reference frames were related directly using the corresponding Lorentz transformations. Our numerical studies revealed that, in the case of a uniformly moving dielectric slab, the angle of incidence for SPP-wave excitation is highly sensitive to (i) the ratio β of the speed of motion to speed of light in free space and (ii) the direction of motion. When the direction of motion is parallel to the plane of incidence, the SPP wave is excited by p-polarized (but not s-polarized) incident plane waves for low and moderate values of β, while at higher values of β the total reflection regime breaks down. When the direction of motion is perpendicular to the plane of incidence, the SPP wave is excited by p-polarized incident plane waves for low values of β, but s-polarized incident plane waves at moderate values of β, while at higher values of β the SPP wave is not excited. In the case of a uniformly moving metal film, the sensitivity to β and the direction of motion is less obvious.     

三层不对称人工电磁材料界面处表面等离子体激元的理论研究

从P和S偏振出发.研究了由常规材料/左手材料/负介电常数材料、及常规材料/左手材料/负磁导率材料这两种三层不对称结构界面上表面等离子体激元(Surface plasmon polaritons,SPPs)的存在区域、色散曲线及其激发.观察到表面等离子体激元的性质强烈地依赖于人工电磁材料的组成参量,例如介质板的厚度和等离子体的频率.最后,使用衰减全反射(Attenuated total reflection,ATR)技术,探究了激发和观察表面等离子体激元的可能性.并针对P和s偏振两种情况计算了衰减全反射光谱.     

[Russian Text Ignored]

The stability of the electromagnetic plasma confinement by powerful external s-polarized pump waves is considered. The parametric excitation of standing electromagnetic waves along the plasma boundary with frequencies close to the frequency of the pump wave leads to a periodic density modulation of the plasma boundary. The density disturbances along the direction of the external wave field are connected to the excitation of transverse p-polarized surface waves while the modulation in the direction perpendicular to the pump field are created by the parametric interaction between the external wave and s-polarized trapped leaking oscillations. Only when the leaking waves are excited the scale length of the modulation is larger than half the free space wave length of the incident radiation.     

Cherenkov terahertz radiation from Dirac semimetals surface plasmon polaritons excited by an electron beam

We demonstrate a physical mechanism for terahertz(THz) generation from surface plasmon polaritons(SPPs). In a structure with a bulk Dirac semimetals(BDSs) film deposited on a dielectric substrate, the energy of the asymmetric SPP mode can be significantly enhanced to cross the light line of the substrate due to the SPP-coupling between the interfaces of the film. Therefore, the SPPs can be immediately transformed into Cherenkov radiation without removing the wavevector mismatch. Additionally, the symmetric SPP mode can also be dramatically lifted to cross the substrate light line when a buffer layer with low permittivity relative to the substrate is introduced. In this case, dual-frequency THz radiation from the two SPP modes can be generated simultaneously. The radiation intensity is significantly enhanced by over two orders due to the field enhancement of the SPPs. The radiation frequency can be tuned in the THz frequency regime by adjusting the beam energy and the chemical potential of the BDSs. Our results could find potential applications in developing room temperature, tunable, coherent, and intense THz radiation sources to cover the entire THz band.     

Lossy effects on the lateral shifts in negative-phase-velocity medium

Theoretical investigations of the lateral shifts of the reflected and transmitted beams were performed, using the stationary-phase approach, for the planar interface of a conventional medium and a lossy negative-phase-velocity medium. The lateral shifts exhibit different behaviors beyond and below a certain angle, for both incident p-polarized and incident s-polarized plane waves. Loss in the negative-phase-velocity medium affects lateral shifts greatly, and may cause changes from negative to positive values for p-polarized incidence.     

Extraordinary THz transmission through subwavelength semiconductor slits under antiparallel external magnetic fields

We theoretically study the resonant transmission of electromagnetic waves at the THz frequencies through subwavelength semiconductor slits under external static magnetic fields. The dispersion relations of the surface plasmon polaritons (SPPs) inside a subwavelength slit are analytically derived. It is found that the SPPs propagating along one direction and its reverse are symmetric when parallel external magnetic fields are applied, but are asymmetric when antiparallel external magnetic fields are applied. The transmission properties of periodic subwavelength semiconductor slit arrays with the antiparallel magnetic fields in each unit cell are investigated by the mode expansion technique. The two significant transmission characteristics are observed: (i) The resonant peaks are redshifted with increasing external magnetic fields; (ii) The transmissions in the two opposite directions through the slit arrays are asymmetric. The origin of the transmission asymmetry is reasonably explained by the magnetic-field induced asymmetric SPP propagation losses.     

Brewster Anomalies in Opaque Random Amorphous Multilayers a-Si:H/a-Si3N4+x:H

Reflectance anomalies of random amorphous multilayers are shown to be different dependence on the incident angle for s- and p-polarized light by simulation. Disappearance of these anomalies has especially been observed for p-polarized light propagation at a certain incident angle. It is shown that this incident angle is the extended Brewster angle defined for opaque materials. This phenomenon, i.e., the disappearance of reflectance anomalies, is the Brewster anomaly in random amorphous multilayers made with absorbent materials. Preliminary results of experiments are also presented.     

Size effects in the internal reflection in gold cluster films in polarization modulation experiments

The internal reflection in gold nanocluster films in the Kretschmann geometry is studied using polarization modulation of electromagnetic radiation. The reflection coefficients R _s and R _p for s- and p-polarized light, respectively, as well as their difference ΔR = R _s − R _p , are measured as functions of the angle of incidence of electromagnetic radiation at different wavelengths in the range of 0.6–1.6 μm. A topological size effect is found in the interaction of light with the cluster electronic system, which consists of the fact that the surface plasmon resonance in gold cluster films can be excited by both p- and s-polarized light. It is found that the magnitude and the sign of curvature of the angular dependence of ΔR are related to the degree of resonance with light of either only p-polarization or both polarizations simultaneously.     

Dispersive characteristics of surface plasmon polaritons on negative refractive index gratings

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.     

The nature of the vectorial photoelectric effect in the threshold energy region

Summary An immediate correlation has been proved to exist between the vectorial photoelectric effect and electronic surface structure modified due to adsorption. Experimental studies were performed for Cs overlayers on W(110) and Si(111) faces using visible exciting photons with energies below those of both bulk and surface plasmons. Considerable (more than 20 fold) growth of the effect was observed forp-polarized light in the vicinity of threshold as the light frequency approached the position of the maximum of local density in the surface-state band. A special case of the vectorial photoelectric effect forp-polarized light has been found in the absence of bulk photoemission excited bys-polarized light. Our results prove that the anomalous vectorial photoelectric effect is caused by the normal electric vector component of thep-polarized light under appropriate conditions for the particular photoemission enhancement on the surface. The effect can be related to optical absorption by the surface-state band and to subsequent electron emission into the vacuum, the normal electric vector component of thep-polarized light being essential for both processes.     

Reconstruction of the coordinate dependence of the diagonal form of the dielectric permittivity tensor of a one-dimensionally inhomogeneous medium

We demonstrate the possibility of a unique reconstruction of the coordinate dependence of all dielectric permittivity tensor components of an absorbing one-dimensionally inhomogeneous plate with any symmetry (except for 1, 2, and m classes) and a negligibly small spatial dispersion. This reconstruction can be performed, the zone of the strong frequency dispersion of the medium inclusive, provided that the reflection and transmission coefficients for the p- and s-polarized plane monochromatic waves are known in a certain range of incidence angles.     

Control of absorption spectrum of a one-dimensional resonant photonic crystal

The crystal under consideration is a layered structure consisting of alternating layers of two materials, one of which is a resonantly absorbing gas. It is shown that the combination of the dispersion of an atomic gas with the dispersion of a photonic-bandgap structures allows one to efficiently control the transmission spectra of s- and p-polarized modes in these combined systems. It is found that the spectrum is highly sensitive to the position of the gas resonance frequency with respect to the bandgap edge and to a change in the gas pressure. The transmission, reflection, and absorption spectra of the resonant photonic crystal are studied at an angle of incidence equal to the Brewster angle of a seed photonic crystal. Possible applications of the found particular features of the dispersion of resonant photonic crystals are discussed.     

Common-path double-pass optical interferometry using a wire-grid polarizer as a reference mirror

A novel common-path double-pass optical interferometer that employs a wire-grid polarizer (WGP) as a reference mirror is presented. When a laser beam polarized at 45° relative to the wire grid is incident on the WGP, the polarization component parallel to the grid direction (s-polarized beam) is reflected and is used as a reference beam. The perpendicular component (p-polarized beam) passes through the WGP coupled with a quarter-wave plate and serves as a probe beam, with its polarization transformed as p, right-circular, s, left-circular, and p, to irradiate the sample surface twice in order to double the phase change due to displacement of the sample. This beam is then retransmitted through the WGP, where it recombines and interferes with the reference beam. Preliminary experiments demonstrate that the WGP performs successfully as a reference mirror, and that the interferometer has a potential displacement sensitivity as low as 0.1 nm.     

Surface plasmon polariton at the interface of dielectric and graphene medium using Kerr effect

We theoretically investigate the control of surface plasmon polariton(SPP) generated at the interface of dielectric and graphene medium under Kerr nonlinearity. The controlled Kerr nonlinear signal of probe light beam in a dielectric medium is used to generate SPPs at the interface of dielectric and graphene medium. The positive, negative absorption, and dispersion properties of SPPs are modified and controlled by the control and Kerr fields. A large amplification(negative absorption) is noted for SPPs under the Kerr nonlinearity. The normal/anomalous slope of dispersion and propagation length of SPPs is modified and controlled with Kerr nonlinearity. This leads to significant variation in slow and fast SPP propagation. The controlled slow and fast SPP propagation may predict significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster, and sensing technology.     

Parametric interaction of space-charge waves in asymmetric thin-film <Emphasis Type="Italic">n</Emphasis>-GaAs structures

Based on a theory developed previously, parametric interaction between space-charge waves in thin-film semiconductor structures with negative differential conductivity is analyzed. The analysis is carried out in the approximation that the drift flux of charge carriers has a rigid boundary and under the assumption that the frequency of low-frequency pumping equals the cutoff frequency f _c of waves being amplified (f _c roughly equals 30 GHz in our case). For asymmetric structures, a general multimode set of coupled equations is reduced to a pair of differential equations for the excitation amplitudes of the fundamental space-charge mode at the signal frequency ω_s and idler frequency ω_i=ω_s−ω_p. The equations are solved numerically for n-GaAs-based structures, and the solution obtained is discussed.     

Simulations of Two-Dimensional Photon Scanning Tunneling Microscope by Boundary Integral Equation Method: p-polarization

Accurate simulations of a two-dimensional photon scanning tunneling microscope (2D-PSTM) for incident p-polarized waves (TM-mode) have been performed by the boundary integral equations called guided-mode extracted integral equations. The method used in this paper is a global method and the case of uncoated dielectric probe is treated. Complete and rigorous integral equations for a given configuration of 2D-PSTM have been solved numerically by the conventional boundary-element method with high accuracy. Using three universal laws, i.e., the optical theorem, the energy conservation law and the reciprocity relation for incident p-polarized waves, numerical results have been confirmed. The basic physical characteristics of interaction between probe-tip and near-field for incident p-polarized waves are compared in detail with those of incident s-polarized waves (TE-mode) which are previously reported.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES(NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Nearfield Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.     

Modulation polarimetry of the topological effect in gold-organic nanocomposite films

The phenomenon of surface plasmon resonance in composite films consisting of gold nanoclusters in matrices of organic molecular materials calix[4]arene and poly(N-vinylcarbazole) has been investigated. The internal reflection coefficients R _s ² and R _p ² of s- and p-polarized light and their physical difference ρ = R _s ² ? R _p ² have been measured according to the Kretschmann scheme as a function of the angle of light incidence θ at different wavelengths λ in the range 400–1000 nm. The angular characteristics reflect the cluster structure of the films, which is confirmed by electron microscopy. A topological size effect has been revealed. This effect is associated with the dependence of the excitation energy efficiency of surface plasmons on the azimuth of the linearly polarized light, the shape, and the distribution of nanoclusters in the coordinate space. The dependences ρ(λ) demonstrate that the local plasmon resonance is excited by both s- and p-polarized light, whereas the polariton resonance is excited by s-polarized light. The sign of the curvature of the dependence ρ(θ) determines the predominance of the excitation energy efficiency of electromagnetic modes with one of the two states of polarization of the excitation radiation.     

Quantized longitudinal exciton-polaritons in periodic metal–semiconductor nanostructures

We theoretically investigate the optical properties of one-dimensional photonic crystals composed of two alternating layers, namely a semiconductor film and a metallic one. The nonlocal optical response of the semiconductor is here described by using a resonant excitonic dielectric function, whereas the local response function of the metal film is modeled with Drude formula. We calculate optical spectra of the metal–semiconductor 1D photonic crystal for both s- and p-polarization geometries. In both cases the spectra exhibit a rich resonance structure due to the coupling of size-quantized excitons inside the semiconductor film with light. We show the difference between s- and p-polarization reflectivity as the angle of incidence is increased. In the p-polarization geometry, besides transverse exciton-polariton modes, longitudinal polarization waves are excited producing additional spectral resonances. The spectra become radically different when the frequency corresponding to the minimum of the first photonic pass-band is close to the exciton resonance, since such a frequency is distinct for s- and p-polarized modes. We also show how reflectivity spectra for both polarizations are modified with varying the metal filling fraction which controls the width of the gap below the lowest frequency band.