Modelování plazmonických nanostruktur v prostředí COMSOL

Finite element method (FEM) is used to solve the behavior problem of electromagnetic (EM) waves in various structures. COMSOL is widely used commercial software solving range of problems by application of FEM. Guided electromagnetic waves on the boundary between metal and dielectric is called the surface plasmon polariton (SPP). The light is concentrated into smaller area than the diffraction limit and this effect is extremely sensitive to changes in materials. The use of SPP lies mainly in sensor technology. Another possible use is in integrated optics for construction of smaller and faster photonic chips where light is guided by surface plasmon waveguides (e.g. metal-insulator-metal architecture). This diploma thesis should provide the reader with the fundamentals of the plasmonics and especially the possibilities of modeling 2D nanostructures in COMSOL Multiphysics software. The thesis contains several model examples on which the modeling process is shown. As advanced nanostructures we choose the nanostructures that use magneto-optics efects.Pro řešení a popis chování elektromagnetických vln v různých strukturách je často používaná metoda konečných prvků (MKP). Software COMSOL Multiphysics řeší pomocí MKP široké spektrum fyzikálních úloh. Vedená elektromagnetická vlna na rozhraní mezi kovem a dielektrikem se nazývá povrchový plasmon polariton. Světlo je koncentrováno do oblasti, která je menší než difrakční limit, a jeho chování je silně závislé na změnách v materiálu. Povrchové plasmony jsou nejvíce využívány v oblasti senzorů, popřípadě v integrované optice pro konstrukci malých a rychlých fotonických čipů, kde je světlo vedeno pomocí plasmonických vlnovodů (např. architektura kov - izolátor - kov). Tato diplomová práce by měla čtenáři poskytnout základní informace o plasmonice a především o možnostech modelování 2D plasmonických nanostruktur pomocí softwaru COMSOL Multiphysics. Práce obsahuje několik příkladů, na kterých jsou ukázány základní postupy při modelování. Jako pokročilé struktury jsme zvolili struktury využívající magnetooptické jevy.9360 - Centrum nanotechnologiívýborn

Selectively toluene-filled photonic crystal fiber Sagnac interferometer with high sensitivity for temperature sensing applications

In this paper, we theoretically and numerically investigate toluene-filled polarization maintaining photonic crystal fibers (PMPCFs) for temperature sensing application via Sagnac interferometer. We designed a PMPCF with a birefringence of 8.68 x 10(-5), a relative birefringence sensitivity of 26% for 5 degrees C variation and sensitivity of -11 nm/degrees C around 25 degrees C. We study the effects of hole dimensions and fabrication imperfections on the performance of the proposed PMPCF and demonstrate that the PMPCF has a good toleration to any geometrical induced imperfections in the fabrication process of the fiber. Furthermore, we show that the spectral range of the sensor can be easily improved (to values larger than 137 nm) by decreasing the infiltration length of the PMPCF.Web of Science13art. no. 10229

Elektronová struktura a termodynamika v systémech aktinidů karbidů z prvních principů

Import 23/07/2015The fundamental properties of novel nuclear fuel materials ranging from their electronic structure, magnetic, elastic, dynamical, and thermodynamical properties of selected phases in the U-C, Pu-C, and Th-C systems were investigated using first principles calculations. The main aim is to explore the effect of strong electron correlations and the spin-orbit interactions (SOI) on the electronic and magnetic properties as well as on the lattice dynamics of the U-C, Pu-C, and Th-C phases. The present project extends the current knowledge of the electronic structure and material's properties and aim to prepare fundamental grounds for studies with structural carbon vacancies on the electronic and magnetic structure as well as the lattice dynamics of UC1-x, PuC1-x, and ThC1-x at the ground state as well as the thermal expansion of pure phases.Základní vlastnosti nových nukleárních palivových materiálů zahrnující elektronovou strukturu a magnetické, elastické, dynamické a termodynamické vlastnosti vybraných fází v U-C, Pu-C, a Th-C systémů byly spočteny pomocí výpočtů z prvních principů. Hlavním cílem je prozkoumat vliv silných elektronových korelací a spin-orbitálních interakcí (SOI) na elektronické a magnetické struktury, jakož i dynamiku mřížek u fází tvořících UC, Pu-C, a Th-C systémy. Tato práce rozšiřuje stávající znalosti o elektronové struktuře a materiálových vlastnostech a zaměřuje se na získání základních informací, které budou sloužit ke studiu vlivu strukturních uhlíkových vakancí na elektronické a magnetické struktury a dynamiku mřížky UC1-x , PuC1-x a ThC1-x v základním stavu a ke studiu tepelné roztažnosti čistých fází.9360 - Centrum nanotechnologiívýborn

Standard and elegant higher-order Laguerre-Gaussian correlated Schell-model beams

To date, all of the Laguerre-Gaussian (LG) correlated Schell-model beams proposed and studied are restricted to the standard form with the beam mode indices (0, l), termed as a SLG(0l)CSM beam. We propose, for the first time, the elegant and standard higher-order LG correlated Schell-model beams as an extension to a SLG(0l)CSM beam. We develop theoretical formulae to determine the beam mode indices of a vortex beam and describe propagation effects of such beams. We demonstrate that by controlling the beam mode indices, one can produce different intensity distribution patterns during propagation, for example, a dark or solid core surrounded by bright concentric rings. Moreover, using our proposed beams, we illustrate how single-layer and multi-layer adjustable optical cages can be formed near the back of the focal zone of a lens. As anticipated, the proposed beams may find important applications in particle trapping, optical manipulation and optical communications.Web of Science218art. no. 08560

Numerical Approach for Studying the Evolution of the Degrees of Coherence of Partially Coherent Beams Propagation through an ABCD Optical System

In this paper, we propose a numerical approach to simulate the degree of coherence (DOC) of a partially coherent beam (PCB) with a Schell-model correlator in any transverse plane during propagation. The approach is applicable for PCBs whose initial intensity distribution and DOC distribution are non-Gaussian functions, even for beams for which it is impossible to obtain an analytical expression for the cross-spectral density (CSD) function. Based on our approach, numerical examples for the distribution of the DOC of two types of PCBs are presented. One type is the partially coherent Hermite−Gaussian beam. The simulation results of the DOC agree well with those calculated from the analytical formula. The other type of PCB is the one for which it is impossible to obtain an analytical expression of CSD. The evolution of the DOC with the propagation distance and in the far field is studied in detail. Our numerical approach may find potential applications in optical encryption and information transfer