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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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Time-resolved laser spectroscopy of nanomaterials
Kozák, Martin ; Trojánek, František (advisor) ; Šimurda, Miroslav (referee)
This diploma thesis is oriented to study of nonlinear properties of semiconductor nanocrystals using ultrashort femtosecond pulses. There is a detailed description of theory and experimental setup of the z-scan method, which can be used to measure the nonlinear refractive index and the two-photon absorption coefficient. In theoretical part we describe the influence the quality of laser beam, quality and thickness of the sample on measurements. There are numerical simulations of the measurements influenced by these parameters. This theory is used for processing of the measured dates by a program, which is attached to this thesis on CD. In experimental part we measured nonlinear refractive indeces of diamond nanocrystals fabricated by the PECVD method, silicon and CdS nanocrystals in glass matrices. One part of this thesis deals with the preparation and optimalization of the experimental setup and increasing the signal/noise ratio.
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Nonlinear optical properties of metals
Gindl, Adam ; Kozák, Martin (advisor) ; Žídek, Karel (referee)
We introduce fundamental nonlinear optical effects and various methods of their observation. Firstly we describe the essential theory of second-harmonic generation from a metallic boundary in detail. In the experiment, we observe this effect on silver and aluminium mirror. Then we introduce the Z-scan method, which allows us to determine the nonlinear refraction index and absorption coefficient from the measurement of the transmittance of the sample if this transmits light in the visible spectrum. A simple modification of this method permits the measurement of nonlinear optical parameters from the sample's reflectance also for materials that reflect light in the visible region. We focus on applying this method in the experiment for siliceous glass, silver, aluminium, dielectric and siliceous mirrors and optical filter OD 0,5.
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Measurement of third harmonic generation efficiency in semiconductor nanocrystals
Sedláčková, Eva ; Kozák, Martin (advisor) ; Veselá, Petra (referee)
The goal of this work was to observe third harmonic generation in semiconductor nanocrystals and to determine the efficiency of this nonlinear-optical phenomenon. Samples used for examination included silicon, diamond and zinc oxide nanocrystals. Using the measured efficiency of third harmonic generation and the parameters of infrared laser pulses used for the generation, we were able to determine the approximate value of the third order nonlinear susceptibility of the materials used in this study. Besides third harmonic generation we observed high harmonic generation in zinc oxide samples up to the ninth order.
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Diagnostics of relativistic electron beams from laser accelerators
Bratko, Maroš ; Nejdl, Jaroslav (advisor) ; Kozák, Martin (referee)
Since the rise of high-energy particle physics in the 20th century, demands for radio-frequency particle accelerators have been increasing, leading to facili- ties occupying tens of square kilometers, requiring massive infrastructure, and having a very high cost. A promising alternative is laser wakefield acceleration, commonly referred to as LWFA, which is based on the interaction of intense laser pulse with the plasma. This technology produces accelerating fields four orders of magnitude larger than radio-frequency particle accelerators, greatly reducing its size. To evaluate the quality, stability, and reliability of the LWFA, properties of electron bunches emerging from the accelerator have to be inves- tigated. The most important properties of electron bunches include the bunch charge, i.e. number of electrons in the bunch, energy distribution, divergence, bunch size, beam emittance, and pointing stability. This thesis is focused on the tools and detectors necessary for measuring these properties. 1
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