Unit:
Department of PhysicsLibrary of the School of Science
Author:
Baskourelos Konstantinos
Dissertation committee:
Κοσμάς Λ. Τσακμακίδης, Επ. Καθηγητής Τμήμα Φυσικής, ΕΚΠΑ,
Νικόλαος Στεφάνου, Καθηγητής Τμήμα Φυσικής ΕΚΠΑ,
Tomasz Stefański, Αναπλ. Καθηγητής, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 80-233 Gdansk, Poland.
Δημοσθένης Σταμόπουλος, Αναπλ. Καθηγητής, Τμήμα Φυσικής ΕΚΠΑ,
Ιωάννης Λελίδης, Αναπλ. Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ,
Δημήτριος Φραντζεσκάκης, Καθηγητής, Τμήμα Φυσικής ΕΚΠΑ
Μαρία Καφεσάκη, Καθηγήτρια, Τμήμα Επιστήμης και Τεχνολογίας Υλικών, Πανεπιστήμο Κρήτης
Original Title:
Light transmission through holes in the deep subdiffractional regime using topological structures
Translated title:
Light transmission through holes in the deep subdiffractional regime using topological structures
Summary:
The subject of the herein Thesis is a novel technique for the efficient transmission and energy focusing on the micro- and nano-scales, particularly for the transmission of light through holes or slits in the deep subdiffractional regime (i.e., significantly smaller than the operating wavelength). This technique has many important advantages over the conventional techniques for the same task, and it could affect positive the evolution of the wider field of nanophotonic applications.
The transmission and focusing of light in the micro- and nano-scales is in the core of many
contemporary applications: Optical data writing/storage, heat-assisted magnetic recording
(HAMR), nanoimaging, spectroscopy, sensing, near-field scanning optical or thermal nanoscopy, thermal scanning probe lithography, nanoscale thermometry, and others such these. In all these applications, there is the requirement to focus with high efficiency ∼100 μW of power to a ∼10 nm (or less) spot on a planar surface. This is a light intensity extremely high, many orders of magnitude larger than the light intensity encountered in everyday physical phenomena (e.g., the intensity of sunlight on the surface of the earth, or the light intensity attained with an optical lens). Optics poses a threshold to the light that can be transmitted and focused from a hole of a given diameter (Bethe’s limit). This threshold makes the aforementioned applications very difficult to realize.
The standard technology attaining the focusing of light in the nanoscale is the gold-coated tapered optical fibers, widely used in Near-field Scanning Optical Microscopes (NSOMs). The optical transmission efficiency of NSOM probe tips is typically between 10−5 - 10−4 (or less).
The herein proposed technique, called APOTUS-HM (APOTUS: Almost Perfect Optical Transmission Through Unstructured Single holes; HM: Hole Method), is a way to overcome the threshold posed by Bethe’s limit. APOTUS-HM provides a transmission coefficient significantly higher than the other established techniques, that ideally approaches unity.
At the same time its basic idea is simple and quite easy to realize in practice.
APOTUS-HM is founded on three main pillars: (i) unidirectionality in propagation, (ii) immunity in dispersion and nonlocality, and (iii) extraordinary optical transmission (EOT). The basic principle of APOTUS-HM is as follows. Using special materials, it is imposed on a wave to propagate in a waveguide only forwards – unidirectionally. At the end of the waveguide there is a hole with the appropriate diameter for the focusing. When the wave arrives at the end of the waveguide, as it cannot move backwards, it is forced to pass through the hole, no matter how small the hole is, and thereby to be focused in front of it.
Despite the simplicity of the above idea, to realize successfully an APOTUS-HM device, there are many subtle theoretical topics that must be studied and understood. In the herein thesis it is made an attempt to present how to implement efficiently the three pillars of the technique mentioned above and the basic theory behind them, giving in this way a background for the better understanding and for further improving the efficiency of the technique. The unidirectionality and immunity of propagation in nonlocal effects is attained using special, optically-topological materials, whose use and basic theory is also explained in some detail in the Thesis.
Main subject category:
Science
Keywords:
Berry phase, Berry connection, Berry flux, Berry curvature, Chern numbers, Chern theorem, Bulk-Edge Correspondence, Berry phase and Chern number of the electronic bands, Wilson Loop, Hybrid Wannier Charge Center, Time Reversal Symmetry, TRS, Broken Time Reversal Symmetry, broken TRS, Helical states, Topological Insulators, Topological Photonics, Optical resonators, Extraordinary Optical Trasmission, EOT, Surface MagnetoPlasmon, SMP, temporal coupled mode theory, perfect magnetic conductor, PMC, APOTUS-HM
Number of references:
293
