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Modelling of Pulse Propagation in Nonlinear Photonic Structures
Sterkhova, Anna ; Richter, Ivan (referee) ; Samek, Ota (referee) ; Petráček, Jiří (advisor)
V současnosti jsme svědky stále zvyšujících se nároku na rychlost přenosu a zpracování signálu a kapacitu pamet’ových zařízení. Proto se pozornost výzkumných pracovníku zaměřuje k plně optickým zařízením, která by mohla splnit zmíněné požadavky. Jednou z intenzívně zkoumaných možností je využití mikroprstencových optických rezonátoru. Při výzkumu je nutné využít numerických metod, které simulují šíření optického záření v dané struktuře. K tomuto účelu existuje celá rada metod, které se liší v efektivitě výpočtu, použitých aproximacích, i možnostech použití. Cílem této práce bylo vyvinout dvě jednoduché a praktické numerické metody pro modelování šíření pulzního záření v nelineárních vlnovodných strukturách. Přítom bylo požadováno, aby, na rozdíl od obecně známé a často využívané metody konečných diferencí v časové oblasti (FD-TD), bylo možné metody snadno aplikovat při studiu nelineárních struktur založených na mikroprstencových rezonátorech. Proto vyvinuté metody používají některé aproximace, zejména aproximaci pomalu proměnné obálky. Výhodou metod je vysoká rychlost a skromné požadavky na výpočetní zdroje. Obě metody vycházejí ze zkutečnosti, že naprostá většina nelineárních struktur založených na mikroprstencových rezonátorech se skládá ze dvou základních prvku: obyčejných vlnovodu a vlnovodných vazebních clenu. První metoda řeší vázané parciální diferenciální rovnice, které popisují šíření obálky pulzu ve struktuře. Přitom je použito tzv. „up-wind“ schéma vhodné pro parciální diferenciální rovnice popisující šíření vln. Druhá metoda vychází z první; rozdíl je v popisu vazby mezi dvěma vlnovody. Pokud se v první metodě uvažuje realistická vazba rozložená na určité délce, pak druhá metoda je založena na představě vazby nacházející se v jednom místě. Díky tomu je možné integrovat příslušné rovnice a dosáhnout výrazného urychlení výpočtu. Kvazianalytický charakter druhé metody umožňuje dále snadnou klasifikaci různých typu ustálených řešení. Vzhledem k těmto vlastnostem byla druhá metoda využita k výzkumu samovolné generace optických pulzu ve strukturách skládajících se z vázaných prstencových rezonátoru. Obě metody, které byly vyvinuty během této práce, představují rychlé a fyzikálně názorné alternativy k metodě FD-TD, a tak lze očekávat, že mohou hrát důležitou roli při výzkumu nelineárních vlnovodných struktur.
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Study of optical properties of organic materials for nonlinear optical applications
Hrbková, Silvie ; Hrabal, Michal (referee) ; Vala, Martin (advisor)
This work deals with a development of a method for determination of two-photon parametres and its application. The theoretical part includes a description of two-photon absorption processes, most frequently used methods to determine two-photon cross sections and a summary of molecules researched to date in the field. The molecules studied in this work are Rhodamin B and Rhodamin 6G in ethanol, which are applied as standards for the implementation of the method. After that, Diketopyrrolopyrroles U24, U37, U49 and U50 dissolved in DMSO, toluene, acetone and chloroform, are researched. Basic optical characteristics - absoption and emission spectra were experimentally acquired for all the materials. Two-photon characteristics were obtained using a picosecond laser and a Two-Photon Excited Fluorescence (TPEF) method. TPA cross-sections and TPA spectra of Rhodamin B and Rhodamin 6G were measured and discussed. Subsequently, this work focuses on absorption and emission solvatation processes of the selected Diketopyrrolopyrroles. These processes indicate their two-photon efficiency. Finally, TPA spectra of the substances are discussed. Contribution of this work is a developed method for measuring the two-photon characteristics suitable for further use. The outcomes achived, enable extensive research of the Diketopyrrolopyrrols characteristics with the use of the measured standards of the Rhodamin B and Rhodamin 6G.
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Novel Molecular Materials for Optics - Synthesis and Characterization of 5-aminotetrazole Salts
Pospíšil, Stanislav ; Zábranský, Martin (advisor) ; Tyrpekl, Václav (referee)
Title: Novel Molecular Materials for Optics - Synthesis and Characterization of 5-aminotetrazole Salts Author: Stanislav Pospíöil Department: Department of Inorganic Chemistry Supervisor: Mgr. Martin Zábransk˝, Ph.D., Department of Inorganic Chemistry Advisors: Prof. RNDr. Ivan N mec, Ph.D., RNDr. Irena Matulková, Ph.D., De- partment of Inorganic Chemistry Abstract: Nonlinear optics is currently an important field for the development of areas such as laser physics or telecommunications, and its understanding is essen- tial for development of new technologies. Its development can also be aided by the investigation of various crystalline materials, such as salts containing cations and anions derived from polarizable organic molecules, exhibiting essential properties for nonlinear optics. This bachelor thesis is focused on preparation of crystalline forms of these compounds. These are salts of simple, nitrogen-rich bases with 5- aminotetrazole. Bigunidium 5-aminotetrazolate, guanidinium 5-aminotetrazolate and aminoguanidium 5-aminotetrazolate were prepared and further characteri- zed. The structures of the latter salts were solved from X-ray di raction data. The methods of spectral vibrational analysis supplemented with nuclear magne- tic resonance and powder di raction were applied to these prepared compounds....
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Novel materials for NLO applications based on guanidine derivatives - crystal engineering and detailed characterisation
Kohúteková, Soňa ; Němec, Ivan (advisor) ; Kalbáč, Martin (referee) ; Vlčková, Blanka (referee)
Title: Novel materials for NLO applications based on guanidine derivatives - crystal engineering and detailed characterisation Author: Mgr. Soňa Kohúteková Department: Department of Inorganic Chemistry Supervisor: prof. RNDr. Ivan Němec, Ph.D. Abstract: This doctoral thesis is focused on the preparation and characterisation of new compounds for potential application in nonlinear optics (NLO). Four molecules containing guanidine fragment were chosen as the carriers of NLO properties - aminoguanidine, diaminoguanidine, N-guanidine-formamide and 1H-pyrazole-carboxamidine, according to the promising preliminary results of hyperpolarizability values obtained by quantum-chemical calculations. Experimental work was divided into two main directions of preparation of new crystalline materials - preparation of perovskite metal-organic frameworks (MOFs) and molecular crystals. In the first group of studied materials, target molecules were expected to occupy cavities of frameworks built by formate anions coordinated to metal cations. In the second group, in the molecular crystals, carriers of NLO properties were co-crystallised with selected inorganic anions to prevent the formation of centrosymmetric dimers and to influence the desired crystal packing. Prepared materials were characterised mainly by the means of...
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Preparation and characterization of crystalline materials - salts of N-guanylglycinium and guanidinium
Skopalík, Jiří ; Matulková, Irena (advisor) ; Zákutná, Dominika (referee)
The scope of this bachelor thesis is the preparation and study of new salts, which can be obtained from systems N-guanylglycine - inorganic acid and guanidine - amidosulfuric acid, as new materials with potential for applications in nonlinear optics. Prepared crystalline salts of N-guanylglycinium - i.e. chloride, two hydrogenphosphites and sulfate dihydrate along with guanidinium amidosulfate were characterized by methods of vibrational spectroscopy (infrared and Raman) and X-ray diffraction (single crystal and powder methods). To estimate the nonlinear optical properties and for the interpretation of the vibrational manifestations of N-guanylglycinium cation, quantum-chemical calculations were performed. Finally, for two non-centrosymmetric N-guanylglycinium hydrogenphosphites, the efficiency of second harmonic generation was determined for powder samples.
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Calculation of vibrational SFG spectra from molecular dynamics simulations
MUSIL, Patrik
In this thesis, implementation of calculation vibrational Sum-Frequency Generation (SFG) spectra from classical molecular simulations of aqueous solutions in the O-H vibrations region is presented. The key part of the thesis was significant improvement of the original codes used by the group of Prof. Marie-Pierre Gaigeot to post-process ab initio molecular dynamics trajectories to predict vibrational SFG spectra and apply it to classical molecular dynamics simulations. Particular attention was paid to modifying and optimizing the code for processing much larger systems (number of molecules) and much longer trajectories (longer simulation times), allowing to take advantage of classical simulations to work on larges scales than the ab initio simulations. The code also integrates calculations of contributions from water O-H bonds and surface hydroxyls. As a new feature, calculation of cross-correlations among molecules was implemented. The performance of the resulting codes is verified and the influence of classical molecular simulation parameters, as well as parameters entering the SFG spectra calculations, on the calculated vibrational SFG spectra is studied for fluorite/water interface.
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Preparation and characterization of novel molecular materials for nonlinear optics
Mathauserová, Jana ; Němec, Ivan (advisor) ; Nižňanský, Daniel (referee)
The main issue of this bachelor thesis is the investigation of salts and cocrystals of biuret and 2-aminopyrimidine in consideration of their usage in the field of nonlinear optics. The first attempt of this thesis was preparation of compounds combining biuret with organic or inorganic acids, urea and biguanide. The second part is focused on the searching of new salts of 2-aminopyrimidine and on further characterisation of its formerly prepared compounds. The methods employed to investigate the prepared materials include vibrational spectroscopy and X-ray diffraction analysis. The theoretical quantum mechanical calculations were used to predict the nonlinear optical properties of selected molecules and also for the interpretation of the recorded vibrational spectra. Measurements of second harmonic generation efficiency of selected powder samples were performed.
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Investigation of new materials for second harmonic generation
Brajer, Martin ; Němec, Petr (advisor) ; Žídek, Karel (referee)
In these bachelor thesis optical properties of materials are studied. This materials are purposefully prepared for effective second harmonic generation (SHG) and for its usage in optoelectronics. Specificely we will measure the first hyperpolarizibility. Non-coherent phenomenon of hyper-Rayleigh scattering will be used. Considering its incoherence, the effect is very weak. It's necessary to use a strong source of light, pulse laser and a sensitive detection device, photomultiplier. Samples are prepared in cooperating chemical laboratories of Faculty of Science of Charles University in Prague. Additionally, we will discuss participation of two-photon fluorescence in output intensity because of its interchangeability with SHG.
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Preparation and study of novel crystalline materials for nonlinear optics based on nitrogen-containing heterocycles
Kloda, Matouš ; Němec, Ivan (advisor) ; Schwendt, Peter (referee) ; Holubová, Jana (referee)
The presented Ph.D. thesis is aimed at the preparation and characterisation of novel crystalline materials with application potential in nonlinear optics (NLO). The main goal was preparation of crystalline salts and adducts (cocrystals) of selected nitrogen-containing heterocycles with a range of organic and inorganic acids. Based on previous study and quantum- chemical calculations, the following starting heterocycles were selected: 2-aminopyrimidine, 4-aminopyrimidine, 5-aminopyrimidine, 3-amino-1,2,4-triazine and 3-amino-5,6-dimethyl- 1,2,4-triazine. The prepared materials were characterised mainly by X-ray diffraction and vibrational spectroscopy and the interpretation of the vibrational spectra was based on quantum-chemical calculations. The systems based on aminopyrimidines were the first field of study in presented thesis. The thesis represents a finalisation of our previous study focused on inorganic salts and cocrystal in the case of 2-aminopyrimidine. The characterisation of a pair of cocrystals with boric acid was accomplished. The 12 new salts and adducts were prepared and characterised in the case of 4-aminopyrimidine and only one crystalline product - adduct with succinic acid - was obtained in the case of 5-aminopyrimidine. The systems based on 3-amino-1,2,4-triazine and its...
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Ultrafast highly nonlinear processes in diamond
Zukerstein, Martin ; Trojánek, František (advisor) ; Kloz, Miroslav (referee) ; Kužel, Petr (referee)
Intense few-cycle laser pulses can significantly affect the properties of transparent solids during the interaction. These processes take place on femtosecond time scales and they can be studied using ultrafast spectroscopic methods. This dissertation deals with highly nonlinear processes in diamond. In the interaction with a crystalline diamond, we observed a strong nonlinear broadening of the spectrum due to self-phase modulation effect, which allowed us to create a simple technique for compression of pulses from laser oscillator. At the same time, strongly nonlinear five-photon absorption was observed, in which we found a significant anisotropy and dependence on the polarization state. With two-beam pump and probe experiments we present a study of anharmonic phenomena in the dynamics of coherent phonons in diamond, additionally we created a new detection technique of lattice vibrations using multiphoton absorption. Finally, the high time resolution of the experiments revealed that the sub-picosecond electron dynamics strongly depends on the composition and morphology of the polycrystalline diamond thin films. The experimental results of this work provide comprehensive research into the interaction of diamond with few-cycle laser pulses and the development of new spectroscopic methods.
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