Superabsorbing metamaterial wormhole: Physical modeling and wave interaction effects

Abstract

Conjugate-impedance matched superabsorbers are metamaterial bodies whose effective absorption cross section greatly exceeds their physical dimension. Such objects are able to receive radiation when it is not directly incident on their surface. Here, we develop methods of physical modeling of such structures and investigate interactions of the superabsorbers with passing electromagnetic radiation. The particular superabsorbing structure under study is a wormhole comprised of meshes of loaded transmission lines. A theory of electromagnetic wave propagation and absorption in such metamaterial structures is developed. At the frequency of operation, the structure exhibits greatly enhanced absorption as compared to the black body-type absorber of the same size. Peculiar wave absorption effects such as trapping of nearby passing beams of electromagnetic radiation are demonstrated by numerical simulations. Possible modifications of the wormhole structure under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, novel antennas, and sensors. I. INTRODUCTIONFrom wave optics, it is known that the scattering and absorption cross sections of resonant particles can be much greater than that of non-resonant bodies with the same dimensions. 1 For instance, the extinction cross-section in subwavelength particles exhibiting plasmonic or polaritonic resonances can be orders of magnitude greater than the same for a black-body type absorber of a comparable physical size. 2-9 Effectively, such resonant particles are able to collect the incident wave power from an area much bigger than their physical cross section.The same physical principle of optimal resonant absorption is used when designing compact receiving antennas. From the theory of wire antennas 10-12 it is known that a short wire dipole (with length much smaller than half wavelength) is a rather ineffective receiver unless it is loaded with complex impedance Z load (ω) = Z * dip (ω), where Z * dip (ω) is the complex conjugate of the input impedance of the dipole antenna at the frequency ω. Such a conjugateimpedance matched load compensates for the excess reactance of the short dipole antenna, tunes it in resonance with the incident field, and provides for the maximum of the received power. 10 The ultimate limit for the effective receiving area of a resonant dipole is (3/8π)λ 2 (e.g., Ref.2), where λ is the radiation wavelength. Note that this limit is determined by the wavelength rather than by the dimensions of the dipole. If a particle supports higher order multipolar resonances (besides the main electric dipolar mode) at the same frequency ω, its absorption cross section can be made larger than that of a resonant dipole. 8,9 In fact, it can be shown that there is no ultimate upper limit on the effective absorption cross section of a resonant object when more and more multipolar modes of the object pile ...

Analytical and numerical modeling of reconfigurable reflecting metasurfaces with capacitive memory

“…Due to the 45 • rotation of the unit cell, the surface waves that impinge on the MS edges at the right angle have |k x | = |k y | in the rotated coordinate system (x , y ) of the reduced unit cell shown in figure 9. Taking this fact into account, the resulting dispersion equation can be written as [41]:…”

Analytical and numerical modeling of reconfigurable reflecting metasurfaces with capacitive memory

“…Namely, in those simulations we observed excitation of parasitic modes produced by irregularities at the edges. An efficient approach to tackle such effects in the finite-size structures can be (a) (b) devised by using the Bloch wave dispersion theory for the 2D TL-based metamaterials [38].…”

“…Due to the 45 • rotation of the unit cell, the surface waves that impinge on the MS edges at the right angle have |k x ′ | = |k y ′ | in the rotated coordinate system (x ′ , y ′ ) of the reduced unit cell shown in Figure 7. Taking this fact into account, the resulting dispersion equation can be written as [38]:…”

“…The propagation factor in the direction orthogonal to an MS edge is k ⊥ = k x ′ √ 2. Thus, the Bloch impedance Z B for the respective surface modes reads [38]…”

Topological Origin of Electromagnetic Energy Sinks

“…Previous works demonstrated the possibility of concentrating electromagnetic energy in tight regions of space using either tapered plasmonic waveguides [27][28][29] or nonreciprocal surface waves [30][31][32][33][34][35][36][37][38][39]. Other types of electromagnetic energy sinks based on super-absorbing photonic platforms have also been proposed recently [40][41][42]. Most remarkably, it has been shown that in some conditions it is possible to completely stop a propagating nonreciprocal surface wave and that this effect may lead to the formation of hotspots where the electromagnetic fields are greatly enhanced [35][36][37][38][39].…”