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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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Time-resolved laser spectroscopy of nanomaterials
Kozák, Martin
Title: Time-resolved laser spectroscopy of nanomaterials: Study of nonlinearities using z-scan method Author: Martin Kozák Department: Department of chemical physics and optics Supervisor: Doc. RNDr. František Trojánek, Ph.D. Supervisor e-mail adress: Frantisek.Trojanek@mff.cuni.cz Abstract: This diploma thesis is oriented to study of nonlinear properties in 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 two-photon absorption coefficient. In the theoretical part we describe the influence of measurement by quality of laser beam, quality and thickness of the sample. There are numerical simulations of measurements influenced by these parameters. This theory is used for processing of measured dates by a simple program, which is attached to this thesis on CD. In experimental part we were measured nonlinear refractive indeces of diamond nanocrystals fabricated by the PECVD method, silicon and CdS nanocrystals in glass matrices. One part of this thesis was also the preparation and optimalization of experimental setup and increasing the signal/noise ratio. Keywords: Z-scan, Kerr effect, nonlinear refractive index, two-photon absorption, nanocrystals
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Generation of carrier-envelope-stable few-cycle pulses in the mid-infrared spectral region
Peterka, Pavel ; Kozák, Martin (advisor) ; Žídek, Karel (referee)
In this thesis we present the realization of a source of 1.5-cycle carrier-envelope phase stable laser pulses in the mid-infrared spectral region. We used ytterbium laser system generating 1 µm pulses as a pump of setup, where the beam is split into several parts and interact in nonlinear optical media. 2 µJ pulses with duration 18 fs at 50 kHz repe- tition rate are produced. By spectral broadening in crystal GGG, 9,9 fs pulses can be achieved. The mid-IR pulses was characterized by third harmonics generation frequency resolved optical gating in the interferometric configuration. Fourier filtering of the mea- sured interferogram allows for the complete reconstruction of amplitude and phase of the ultrashort pulses generated by our setup. The pulses will in future serve for experimental investigation of ultrafast strong-field phenomena in solids. 1
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Time and spectral properties of emICCD camera
Šatra, Šimon ; Trojánek, František (advisor) ; Kozák, Martin (referee)
In this work we focus on determining the properties of emICCD camera PI-MAX4: 512 EM, which is connected to IsoPlane 320 spectrograph. The first chapter contains a brief description of emICCD detection and a summary of parameters of the camera, spectrograph and basics of Lightfield software. The second chapter is dedicated to descri- bing the utilization rate of the gain function, the spectral resolution and comparing the emICCD camera with a classic CCD camera. This work should provide a summary of the basics about the emICCD camera together with the information which are fundamental to its right operation. 1
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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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Nonlinear optical frequency conversion of few-cycle laser pulses
Koutenský, Petr ; Kozák, Martin (advisor) ; Galář, Pavel (referee)
Title: Nonlinear optical frequency conversion of few-cycle laser pulses Author: 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 the thesis was to achieve generation of second harmonic frequency from ultrashort laser pulses with central wavelength of 780 nm and to compress the generated pulses to the shortest possible time duration. We have studied and optimized the efficiency of second harmonic frequency generation from wide spectrum laser, which generates ultrashort pulses with a duration of few femtoseconds. Firstly we have developed and optimized the experimental setup for the highest power output of the generated second harmonic frequency pulses. Afterwards we measured the duration of the generated pulses using nonlinear optical cross- correlation with the pulses at the fundamental frequency generated by the laser. Cross- correlation was obtained from sum frequency generation in a thin nonlinear BBO crystal. The pulses at the second harmonic frequency were compressed to a duration of 13 femtoseconds by combining wide spectrum mirrors with negative dispersion of group velocities and thin fused silica wedges. These ultrashort pulses will be used in experiments with high time...
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