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Ultrafast dynamics of charge carriers in 2D materials
Koutenský, Petr ; Kozák, Martin (advisor)
Title: Ultrafast dynamics of charge carriers in 2D materials Author: Bc. Petr Koutenský Department: Department of Chemical Physics and Optics Supervisor: RNDr. Martin Kozák, Ph.D., Department of Chemical Physics and Optics Abstract: The goal of this thesis was to study ultrafast dynamics of excitons in monolayers of transient metal dichalcogenides WSe2 and MoS2 using methods of ultrafast laser spectroscopy. We focus on two types of processes in this thesis. We measured ultrafast dynamics of carrier recombination and inter-valley scattering of excitons. We also focused on ultrafast manipulation with excitonic energy levels which allows us to remove the energy degeneracy in different minima of the band structure using coherent optical effects (optical Stark effect and Bloch-Siegert shifts). In the future, the observed phenomena could contribute to developement of new utrafast optical and optoelectronical devices exploting so called valley polarization of electrons in the studied materials. Keywords: Ultrashort laser puses, time-resolved laser spectroscopy, nonlinear op- tics, 2D crystals iii
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Generation of high harmonic frequencies in crystalline materials
Gindl, Adam ; Kozák, Martin (advisor) ; Veselá, Petra (referee)
The interaction of intense ultrashort laser pulses with materials in the strong field regime of nonlinear optics enables the study of electron excitations with high temporal resolution. In this thesis, we focus on the experimental research of high harmonic ge- neration in crystalline silicon. The goal of our study is to reach the modulation of the amplitude and the phase of the generated field using coherence control by a superposition of optical fields at the fundamental and its third harmonic frequency. The modulation of the generated field occurs due to the change of the relative phase shift between the driving fields. The resulting amplitude and phase changes of the high harmonic field are investi- gated for different amplitude ratios of the driving fields using spectroscopic methods and spectral interferometry. The newly introduced spectral interferometry technique enables the measurement of the emission delay of high-energy photons on attosecond time scale. 1
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Suricata Module for IBM QRadar
Kozák, Martin ; Žádník, Martin (referee) ; Hranický, Radek (advisor)
This work integrates the Suricata program into the QRadar system. The main objective of this work is to design and implement a DSM module in QRadar system that can analyze the records from Suricata. The events can then be investigated in the QRadar system environment. Another objective is to design an application that displays the data detected by the Suricata program. The application can be installed in the QRadar environment and used with other built-in components. The application is programmed in the Flask library using Jinja2 templates. The application includes two tabs that display events in different graphs and table.
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The importance and use of wetland plants in the past and present times
KOZÁK, Martin
This paper deals with a research on the importance and use of wetland plants in history and present. The aim of the work is to collect information and critically assess the information on the importance of wetland plants to human society in the past and present including their uses. The review builds on the existing treatment of the topic in the Czech language and extends it with information published in foreign-language scientific and professional literature over the last 20 years and summarizes knowledge especially on wetlands, useful, invasive and endangered wetland plants.
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Classical and quantum model of 1D dynamics of free electron in ponderomotive potential of an optical beat wave
Kuchař, Marek ; Kozák, Martin (advisor) ; Chlouba, Tomáš (referee)
Inelastic scattering of freely propagating electrons on light waves is currently a studied topic because of potential applications in advanced electron microscopy and diffraction. The interaction is typically described using an approximation, in which we assume that the electron's velocity nearly does not change during the interaction. In this thesis we aim to describe the dynamics of electrons in an interaction potential generated by an optical wave beyond this regime. In classical description we solve the nonlinear equation of motion and while addressing the problem using quantum mechanical description we first use parabolic approximation of the interaction potential and then we also study the evolution of a free electron wavefunction in a full periodic potential. Using numerical simulations we show the expected evolution of the electron spectra during the interaction, based on analytical solutions. 1
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Generation of femtosecond supercontinuum using ultrashort laser pulses with stable carrier-envelope phase
Harabišová, Jana ; Kozák, Martin (advisor) ; Žídek, Karel (referee)
Femtosecond supercontinuum is a nearly ideal source of light for optical spectroscopy due to its extremely broad spectrum and a combination of high temporal and spatial coherence. This thesis is focused on experimental study of supercontinuum generation by ultrashort laser pulses in the mid-infrared spectral region, which belongs to the area of anomalous dispersion regime in most of optical materials. The self-compression of the pulse propagating through the material causes not only extreme spectral broadening but also generation of the so-called dispersive wave. The objective of this thesis is to observe and study the dependence of the generated spectra of the visible light on the absolute phase of the pulse, which is stabilized thanks to the technique of generation of the input pulse based on difference frequency generation. Selected measurements are compared with numerical solution of one dimensional generalized non-linear Schrödinger equation. 1
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Ultrafast dynamics of charge carriers in 2D materials
Koutenský, Petr ; Kozák, Martin (advisor) ; Galář, Pavel (referee)
Title: Ultrafast dynamics of charge carriers in 2D materials Author: Bc. Petr Koutenský Department: Department of Chemical Physics and Optics Supervisor: RNDr. Martin Kozák, Ph.D., Department of Chemical Physics and Optics Abstract: The goal of this thesis was to study ultrafast dynamics of excitons in monolayers of transient metal dichalcogenides WSe2 and MoS2 using methods of ultrafast laser spectroscopy. We focus on two types of processes in this thesis. We measured ultrafast dynamics of carrier recombination and inter-valley scattering of excitons. We also focused on ultrafast manipulation with excitonic energy levels which allows us to remove the energy degeneracy in different minima of the band structure using coherent optical effects (optical Stark effect and Bloch-Siegert shifts). In the future, the observed phenomena could contribute to developement of new utrafast optical and optoelectronical devices exploting so called valley polarization of electrons in the studied materials. Keywords: Ultrashort laser puses, time-resolved laser spectroscopy, nonlinear op- tics, 2D crystals iii
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Spectroscopy of semiconductors with ultra-high time resolution
Hanák, Martin ; Trojánek, František (advisor) ; Kozák, Martin (referee)
This thesis is aimed at building and optimization of a new experiment setup for measuring time-resolved transmittance using a pump-probe method. Test measurements were then conducted on a sample of SiV centers in diamond. The theoretical part contains a general description of luminescence of color centers. It then specifically focuses on SiV centers in diamond and describes their structure, electronic and spectral properties in detail. The description of our setup and its optimization is given at the beginning of the experimental part. The dependencies of differential transmittance of SiV centers in diamond on excitation intensity and wavelength were measured and the lifetime of SiV centers was then determined from our measurement results. 1
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Knowledge of rowing between students of Faculty of Physical Education and Sport, Charles University and Faculty of Physical Culture Palacký University Olomouc
Richterová, Nikol ; Janák, Vladimír (advisor) ; Kozák, Martin (referee)
Title: Knowledge of rowing between students of Faculty of Physical Education and Sport - Charles University and Faculty of Physical Culture - Palacký University Olomouc Objectives: The main objective of this work is research on the extent of knowledge about rowing of the students of two sports-oriented university faculties. Another aim is to compare general knowledge of students and comparison of the two selected faculties Methods: To determine the necessary information was used quantitative research, using on-line interviews. Before the interview was modified a questionnaire on the given subject, which was planned for 100 respondents. The research was conducted using an electronic questioning when the questionnaire was completed 119 respondents from Faculty of Physical Education and Sport - Charles University and The Faculty of Physical Culture - Palacký University Olomouc Results: Based on the research results, it is possible to say that knowledge and awareness about the rowing is among respondents rather average. Approximately 75 % of the respondents knew the correct answer in three questions. But to another question stated the right answer only 12 % of respondents. After mutual comparison of the two faculties, it is possible to say that knowledge of rowing are comparable. Keywords: rowing,...
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