Department of Physics
Library of the School of Science

2024-01-14

2024

Kiorpelidis Ioannis-Markos

Φώτιος Διάκονος, Καθηγητής, Τμήμα Φυσικής, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Vincent Pagneux, CNRS Director of Research, Laboratoire d’Acoustique de l’Université du Mans (LAUM)
Georgios Theocharis, CNRS Researcher, Laboratoire d’Acoustique de l’Université du Mans (LAUM)
Vassos Achilleos, CNRS Researcher, Laboratoire d’Acoustique de l’Université du Mans (LAUM)
Κωνσταντίνος Μακρής, Αν. Καθηγητής, Τμήμα Φυσικής, Πανεπιστήμιο Κρήτης
Νικόλαος Στεφάνου, Καθηγητής, Τμήμα Φυσικής, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Ευστάθιος Στυλιάρης, Καθηγητής, Τμήμα Φυσικής, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών

Wave phenomena in one-dimensional space or time varying media

English

Wave phenomena in one-dimensional space or time varying media

The interaction of waves with media possessing spatial or/and temporal fluctuations leads to interesting phenomenology. Within this framework, in the present thesis four wave phenomena are studied: two occurring in spatially-varying media and two in time-varying media. We begin by exploring wave scattering by a finite spatially-periodic setup that is subject to perturbation. Our focus is on perfect transmission resonances (PTRs) and we develop a method for preserving them under asymmetric perturbations. The performed analysis reveals a pairwise connection between PTRs of a spatially-periodic scattering setup with mirror symmetric cells. In the same context of spatially varying media, we compute the localization length of the topological edge modes that are supported in a mechanical mass-spring chain possessing random fluctuations of its stiffness parameters. In the presence of strong chiral disorder the localization length diverges, implying a topological phase transition that is induced purely by disorder. As a next step we consider the case where the couplings of the mechanical mass-spring chain vary with time in a deterministic way. Then this time-varying system can serve as a platform for transferring a topological edge mode. Going beyond the adiabatic limit, we design a protocol for the time-varying couplings that results in a fast and robust transfer and even more leads to amplification of the transferred edge mode. To shed light into the phenomenon of amplification in a time-varying platform, we explore the propagation of a wave in a medium with time-periodic refractive index and with wave dynamics governed by the Mathieu equation. The wave exhibits transient amplification due to the non normal nature of the propagator matrix and we provide numerical evidence that the global amplifying features are provided merely by the monodromy matrix.

Science

perfect transmission resonances, localization length, non-adiabatic state transfer, Mathieu equation, pseudospectrum

No

0

Yes

142

108

File access is restricted until 2025-01-17.

https://pergamos.lib.uoa.gr/uoa/dl/object/3387883