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Controlled Excitation of Magnons through Optically Induced Mie Resonances in Periodic Dielectric Nanostructures
Krčma, Jakub ; Ligmajer, Filip (referee) ; Holobrádek, Jakub (advisor)
Magnonics is a research field which explores the manipulation and propagation of magnetic excitations called spin waves and their quantum counterparts magnons. It holds promise for improving computing and information processing with the prospect of reduced energy requirements and faster operation. A transition to shorter-wavelength spin waves is necessary for device miniaturization and, consequently, reduced power consumption. Currently, the only technique for direct measurement and imaging of nanoscale spin waves is x-ray microscopy, which relies on synchrotron radiation and is very time- and resource-demanding. Therefore, methods are being investigated to extend the commonly used and more easily accessible technique of Brillouin light scattering microscopy and spectroscopy to detect magnons with high wavenumbers. In recent years, we demonstrated that by optically inducing Mie resonances in dielectric structures, we are able to achieve detection of extended magnon wavenumbers. Even though this method allowed measurement of the nanoscale spin waves, wavevector resolution was not achieved. In this work, we have shown, that by introducing periodicity into these dielectric structures, we can not only measure magnons with wavenumbers up to 157 rad/µm (corresponding wavelength is 40 nm), but also achieve wavevector resolution. This exceeds the capabilities of existing characterization techniques and opens up new possibilities, for example, in the study of nonlinear phenomena or skyrmion devices.
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Photonic crystal fibers
Dočkal, Martin ; Tejkal, Vladimír (referee) ; Šporik, Jan (advisor)
This graduation thesis deals with use of unconventional optical fiber with the intention of photonic crystal fiber. There are described types of photonic crystal fiber, their physical, optical and transfer characteristics. There is explained what are the photonic crystals, principle of their function and possible types of crystals. There are also detailed types of photonic fiber commonly used in the optical fiber branch. There is also explained photonic crystal fiber its structure a hierarchy of its types. In this thesis are described and demonstrated different kinds of photonic optical fiber and their use. There is demonstrated principle of one-dimensional periodical structure of Bragg fiber using simulation software. There can be seen graphical comparison of the simulated optical fiber core to commonly obtainable fiber. Outcome of this graduation thesis should be explanation of function of photonic crystal fiber and possibility of finding new type of fiber with optimal dispersion characteristics for use in fiber optics.
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Preparation and testing of SNOM probes
Bobek, Juraj ; Neuman, Jan (referee) ; Spousta, Jiří (advisor)
Fotonická krystalická vlákna (PCF) představují slibný nástroj pro spojení technik známých z mikroskopie rastrovací sondou, elektronové mikroskopie a systémů pro vstřikování plynu. Přivedení světla a přenos pracovního plynu současně do blízkosti vzorku umístěného uvnitř elektronového mikroskopu přináší nové možnosti experimentů. PCF by mohly být použity nejen k charakterizaci nebo modifikaci struktur na mikroskopické úrovni, ale také k jejich výrobě. Tato práce se zabývá výzkumem literárních zdrojů s tématikou fotonických krystalů s důrazem na PCF. Leptání PCF pomocí kyseliny fluorovodíkové bez poškození jejich vnitřní struktury je experimentálně studováno s velkou precizností. Optické vlastnosti závislé na geometrii PCF jsou testovány pro různé modifikace PCF. Dále se práce zabývá spojením PCF s mikroskopií atomárních sil a následnou integrací do elektronového mikroskopu.
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Preparation and testing of SNOM probes
Bobek, Juraj ; Neuman, Jan (referee) ; Spousta, Jiří (advisor)
Fotonická krystalická vlákna (PCF) představují slibný nástroj pro spojení technik známých z mikroskopie rastrovací sondou, elektronové mikroskopie a systémů pro vstřikování plynu. Přivedení světla a přenos pracovního plynu současně do blízkosti vzorku umístěného uvnitř elektronového mikroskopu přináší nové možnosti experimentů. PCF by mohly být použity nejen k charakterizaci nebo modifikaci struktur na mikroskopické úrovni, ale také k jejich výrobě. Tato práce se zabývá výzkumem literárních zdrojů s tématikou fotonických krystalů s důrazem na PCF. Leptání PCF pomocí kyseliny fluorovodíkové bez poškození jejich vnitřní struktury je experimentálně studováno s velkou precizností. Optické vlastnosti závislé na geometrii PCF jsou testovány pro různé modifikace PCF. Dále se práce zabývá spojením PCF s mikroskopií atomárních sil a následnou integrací do elektronového mikroskopu.
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Calculation of optical response of photonic structures by FDTD method
Vozda, Vojtěch ; Veis, Martin (advisor) ; Richter, Ivan (referee)
FDTD method is based on Maxwell's equations and this thesis describe how to make these differential equations computer readable for numerical solution known as the Yee algorithm. Time step dependence on spatial step is examined here in order to obtain stable solution. Discrete Fourier trasform is defined to obtain frequency dependent transmission and reflection coefficients. Programmed simulation is tested on analytically solvable structures even on slightly more complex systems whose optical response was computed by other type of simulation. Finally photonic crystals and their application as biosensors are discussed. Particular shape of photonic crystal is examined in details (frequency spectrum dependence upon spatial resolution, inaccuracy in geometry, different compounds in holes, geometry modification).
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Photonic crystal fibers
Dočkal, Martin ; Tejkal, Vladimír (referee) ; Šporik, Jan (advisor)
This graduation thesis deals with use of unconventional optical fiber with the intention of photonic crystal fiber. There are described types of photonic crystal fiber, their physical, optical and transfer characteristics. There is explained what are the photonic crystals, principle of their function and possible types of crystals. There are also detailed types of photonic fiber commonly used in the optical fiber branch. There is also explained photonic crystal fiber its structure a hierarchy of its types. In this thesis are described and demonstrated different kinds of photonic optical fiber and their use. There is demonstrated principle of one-dimensional periodical structure of Bragg fiber using simulation software. There can be seen graphical comparison of the simulated optical fiber core to commonly obtainable fiber. Outcome of this graduation thesis should be explanation of function of photonic crystal fiber and possibility of finding new type of fiber with optimal dispersion characteristics for use in fiber optics.
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Photonic structures and their preparation
Varga, Marián ; Ondič, Lukáš ; Hruška, Karel ; Potměšil, Jiří ; Libertínová, Jitka ; Kromka, Alexander ; Remeš, Zdeněk
Photonic crystals are periodically structured electromagnetic media, generally possessing photonic band gaps: ranges of frequency in which light cannot propagate through the structure. This periodicity, which length scale is proportional to the wavelength of light in the band gap, is the electromagnetic analogue of a crystalline atomic lattice, where the latter acts on the electron wavefunction to produce the familiar band gaps of semiconductors, and so on, in solid-state physics. Several examples of organisms and structures possessing photonic crystals and iridescence are visible all around us (Morpho didius, Pavo cristatus, Chrysochroa vittata, Chrysina resplendens, …).
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