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Identifier

000423168

Title

Dynamic anapole: realization by metasurfaces made of sculptured and water-based cylinders

Alternative Title

Δυναμικό ανάπολο: υλοποίηση σε μεταεπιφάνειες από διαμορφωμένους ή υδάτινους κυλίνδρους

Author

Τάκου, Ευαγγελία Ε.

Thesis advisor

Οικονόμου, Ελευθέριος
Μακρής, Κωνσταντίνος

Abstract

This thesis consists of two main parts: 1) A presentation of all-dielectric polaritonic metasurfaces consisting of properly sculptured cylinders to sustain the dynamic anapole, i.e. a non-radiating alternating current distribution. This part is an attachment of a paper of which I am the first author, and was recently submitted in Physical Review B. In the paper, two ways for the anapole to emerge are examined; first, by combining modes based on the first and the fourth mixed toroidal Mie resonance of a cylinder made of high permittivity LiTaO₃ and second, by breaking the circular symmetry, enabling substantial toroidal dipole to emerge from the magnetic quadrupole Mie mode. In both designs, the circular cross-section of each cylinder varies periodically along its length in a binary way, from small to large, while its overall circular symmetry has to be broken in order to remove parasitic magnetic modes. Segments of small cross-sections are the main source of the electric dipole Mie mode, while large cross-section segments sustain the fourth, mixed toroidal dipole Mie mode (in the first design) or the hybrid magnetic quadrupole Mie mode (in the second design). The sensitivity of the anapole states to the material dissipation losses is examined leading to the conclusion that the proposed metasurfaces offer a scheme for realistically implementing the anapole in the low THz. 2) Another practical and convenient way for the realization of the dynamic anapole, is to exploit the dielectric properties of water. Being a polar material of adjustable characteristics, water can lead to novel applications, by being incorporated into a many-rod metasurface. The theoretical results evaluate the resilience of the anapole state achieved by a collective toroidal super-mode for implementation in the low GHz; a widely established and accurate in the low GHz, Debye model for the water permittivity was used. The theory is further supported by an experiment conducted in one of the labs at Forth IESL, and then the comparison of theory and experiment is examined concluding to their good agreement, opening thus the path for the utilization of water in various applications.

Language

English

Subject

Anapole moment

Electromagnetic excitations

Mie resonances

Toroidal moment

Αναπολική ροπή

Διεγέρσεις Mie

Ηλεκτρομαγνητικές διεγέρσεις

Τοροειδής ροπή

Issue date