This paper presents theory of new shear horizontal (SH) acoustic surface waves that propagate along the interface of two semi-infinite elastic half-spaces, one of which is a conventional elastic medium and a second one an elastic metamaterial with a negative and frequency dependent shear elastic compliance. This new surface waves have only one transverse component of mechanical displacement, which has a maximum at the interface and decays exponentially with distance from the interface. Similar features are also shown by the acoustic shear horizontal Maerfeld-Tournois surface waves propagating at the interface of two semi-infinite elastic media due to the piezoelectric effect that should occur in at least one semi-space. The proposed new shear horizontal acoustic surface waves exhibit also strong formal similarities with the electromagnetic surface waves of the surface plasmon polariton (SPP) type, propagating along a metal-dielectric planar interface. In fact, the new shear horizontal elastic surface waves possess a large number of properties that are inherent for the SPP electromagnetic surface waves, such as strong subwavelength concentration of the wave field in the proximity of the guiding interface, low phase and group velocity etc. As a result, the new shear horizontal acoustic surface waves can find applications in sensors with extremely high sensitivity, employed in measurements of various physical parameters, such as viscosity of liquids, as well as in biosensors, chemosensors, or a near field acoustic microscopy (subwavelength imaging) and miniaturized devices of microwave acoustics.
The near-field multiple optical trapping using high order axially symmetric polarized beams (ASPBs) is studied for the first time. First, a near-field optical trapping scheme is proposed based on the Kretschmann–Raether configuration, and surface plasmon polaritons (SPPs) field distributions excited by incident ASPBs are calculated, which present a multi-focal-spot pattern and the size of spots is much smaller than that of the diffraction limitation. Then, the gradient forces on Rayleigh dielectric particles formed by the multi-focal-spot focused field are computed, which indicates that multiple ultra-small particles with the refractive index higher than that of the ambient medium can be trapped simultaneously on the metal surface. The number and size of trapped particles can be manipulated by flexibly modifying the polarization order of incident beams, which is expected to enhance the capability of traditional optical trapping systems and provide a solution for massively parallel optical trapping of nanometer-sized particles.
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The prismatic structures for excitation surface plasmon polariton and waveguide modes resonances were investigated. The first structure consists of a glass prism and thin metallic layer deposited on the prism. The second one includes an additional dielectric layer. Plasmon polariton resonance can be observed only for TM polarization at finely tuned structure parameters. Waveguide modes resonance is possible for both polarizations in the presence of the dielectric layer. We show that the first structure has the highest sensitivity of angle minimum reflectivity, whereas the second one has the highest reflectivity sensitivity to the probed liquid refractive index changes.
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We study propagation of surface electromagnetic waves along a metallic surface covered by various layered dielectric structures. We show that strong radiative losses, typical for scattering of a surface wave, can be considerably suppressed when a single dielectric step is substituted by gradient index or periodic layered structure.
Surface plasmon polaritons (SPP), electromagnetic waves coupled to collective free electron oscillations in metal, are of great interest in many fields of science and technology. This branch, which has recently undergone very rapid growth, gives hope to obtain new generation of very fast computer chips, produce more sensitive detectors, directly visualize fragile nanoobjects and design new metamaterials, which are responsible for interesting and counterintuitive phenomena such as reverse refraction and electromagnetic cloaking. The most interesting features and applications of SPP in various fields of technology are presented.
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