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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Testování a optimalizace iontového zdroje / Testing and optimization of an ion source

Glajc, Petr January 2014 (has links)
A thorough description of the testing of a saddle-field ion source is presented in the diploma thesis. The most important experimental results, such as Faraday cup measurements of the ion beam current profile and of the ion energy spectra, are included. Based on these results it is shown that the optimized ion source works correctly and according to the expectations. At the end of the thesis, the development of the ion-optical and construction design of the focusing optics is described. The manufactured optics assembly attached to the ion source is also shown.
42

Studium optických nelinearit v polovodičích a polovodičových nanostrukturách / Studium optických nelinearit v polovodičích a polovodičových nanostrukturách

Kozák, Martin January 2013 (has links)
This Ph.D. thesis is focused on the study of optical nonlinearities and dynamics of excited charge carriers in monocrystalline diamond, nanocrystalline diamond and silicon. The dynamics of high density carriers in bulk diamond is investigated in detail (the transition from excitons and free carriers to electron-hole liquid or plasma). We study the picosecond dynamics of electron-hole liquid condensation using several techniques of time-resolved optical spectroscopy and demonstrate its evaporation by femtosecond laser pulses. We also propose two new optical techniques for measurement of lifetime, diffusion coefficient and surface recombination velocity of excitons in diamond. The results obtained by these techniques are described theoretically using diffusion equation and compared with the results obtained by the transient grating diffraction measurement. Further we study two- and three- photon absorption and nonlinear refractive index in diamond. In nanocrystalline diamond we study the second and third harmonic generation and its physical origin. In superlattices of silicon nanocrystals in SiO2 matrix we investigate the nonlinear transient absorption dynamics and carrier diffusion.
43

Generace fázově stabilních ultrakrátkých pulzů ve střední infračervené oblasti / Generation of carrier-envelope-stable few-cycle pulses in the mid-infrared spectral region

Peterka, Pavel January 2020 (has links)
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
44

Elektros srovės, geometrinės optikos, atomo branduolio fizikos mokomieji bandymai ir jų loginė analizė / Educational Experiments of Electric Current, Geometrical Optics, Atomic Nuclear Physics and Their Logical Analysis

Labanauskaitė, Lina 03 January 2011 (has links)
Bakalauro dabą „Elektros srovės, geometrinės optikos, atomo branduolio fizikos mokomieji bandymai ir jų loginė analizė“ susideda iš įvado, 3 skyrių, išvadų ir 28 literatūros šaltinių. Darbo apimtis 66 puslapiai. Pirmoje ir antroje dalyje apžvelgiama pedagogikos ir psichologijos literatūros šaltinių analizė. Trečioje dalyje yra aprašomi XII klasės fizikos kurso mokomieji bandymai ir jų loginės samprotavimo schemos iš: • Elektros srovės (9 eksperimentai). • Geometrinės optikos (8 eksperimentai). • Atomo branduolio fizikos (5 eksperimentai). Samprotavimo schemos planai padeda mokiniams: suprasti demonstracinio bandymo esmę, nustatyti priežasties – pasekmės ryšius ir priklausomybę, gretinti sąlygas ir išvadas, apibendrinti rezultatus, daryti išvadas. / Bachelor's work „Educational Experiments of Electric Current, Geometrical Optics, Atomic Nuclear Physics and Their Logical Analysis” consists of an introduction, 3 chapters, conclusions and 28 references. Working amount 66 pages. In first and second part gives an overview of pedagogy and psychology analysis of literature source. In third part is described education experiments of physics and their logical reasoning schemes of XII class from: • Electric Current (9 experiments). • Geometrical Optics (8 experiments). • Atomic Nuclear Physics (5 experiments). Reasoning schemes help students to: understand the nature of the demo task, determine cause – effect relationships and dependencies, compare conditions and findings, summarize the results, do conclusions.
45

Nové molekulární materiály pro nelineární optiku - příprava a detailní charakterizace / Nové molekulární materiály pro nelineární optiku - příprava a detailní charakterizace

Mathauserová, Jana January 2013 (has links)
In this thesis both an experimental and computational study of selected prospective materials for nonlinear optics is presented. The main focus was put on 2-aminopyrimidinium hydrogen- phosphite (AMPPO3), a salt with high SHG efficiency and Type I. phase matching properties. AMPPO3 had been studied by our research group and its favourable qualities such as easy preparation, colourlessness, great water solubility and good crystallinity motivated further in- terest and the attempts for the growth of bulk single crystals from thermostated aqueous solu- tions as presented here. The products are meant to be probed by laser in a specific direction to determine the maximum SHG efficiency, so far the polarized microscopy study revealing the extreme dispersion effects is provided. AMPPO3 is an example of H-bond stabilized framework with both organic and inorganic building blocks. The computational study was led as to understand the structure which is typical for one of the classes of compounds exhibiting nonlinear optical properties. DFT implemented in parallel CP2K was used and for the comparison three other optically active materials of sim- ilar composition were studied - urea, guanylurea hydrogenphosphite and 2-aminopyrimidine- boric acid 3/2 cocrystal. After the constrained geometry optimization and cell...
46

Optická charakterizace tenkých vrstev s využitím evolučních technik / Optical Characterization of Thin Films Using Evolutionary Techniques

Horáček, Miloslav Unknown Date (has links)
My master's thesis deals with creating of a suitable evaluation technique that optimizes the optical parameters of the thin films according to the specified requirements of the proposer. This technique will be used at the Faculty of Mechanical Engineering and it should facilitate the evaluation of measurement results of the The Institute of Physical Engineering workers. Research workers use a digital imaging spectrophotometer for some measurements of optical properties of thin films at the institute. My most important task is to process the output data of the spectrophotometer concerning selected thin film. Construed master's thesis describes all the tools and techniques that have been used for the implementation of the program including evolutionary techniques and basics of the thin films optics (within the framework of the electromagnetic optics). As an enclosure, an electronic medium with the source codes of the whole application is provided.
47

Trijų ir keturių bangų parametrinių sąveikų taikymas ultratrumpųjų impulsų generacijai ultravioletiniame, artimajame ir viduriniajame infraraudonajame spektro ruože / Three and four wave parametric interactions for ultrashort pulse generation in the ultraviolet, near and mid-infrared spectral range

Darginavičius, Julius 25 September 2013 (has links)
Pagrindinis šios disertacijos tikslas – sukurti efektyvius trijų ir keturių bangų sąveikomis paremtus metodus ultratrumpiesiems ultravioletinės (UV), artimosios bei vidurinės infraraudonosios (IR) spektro srities impulsams generuoti. Pademonstruota efektyvi Nd:stiklo lazerio harmonikų generacija nekolinearaus keturbangio skirtuminio dažnio žadinimo metodu izotropinėse terpėse. Disertacijoje taip pat eksperimentiškai ir teoriškai nagrinėjama galimybė stiprinti 10 fs trukmės UV impulsus. Pateikėme du metodus derinamo bangos ilgio IR impulsams generuoti naudojant komercinę Ti:safyro lazerio ir nekolinearaus optinio parametrinio stiprintuvo sistemą. Pirmasis metodas remiasi keturių bangų sąveikomis ir leidžia generuoti 20 μJ energijos, <30 fs trukmės impulsus 1−1.5 μm spektro ruože. Antrojo šaltinio veika remiasi skirtuminio dažnio generacijos bei optinio parametrinio stiprinimo sąveikomis BBO kristaluose. Sukurtas stiprintuvas, generuojantis dviejų optinių ciklų trukmės, stabilios gaubtinės fazės, 2 μm bangos ilgio impulsus ir pademonstruotas jo taikymas itin plataus spektro superkontinuumo generacijai plačios draustinės juostos kietojo kūno terpėse. Galiausiai, ištirta vienalaikė trečiosios harmonikos ir superkontinuumo generacija skaidriose dielektrinėse terpėse, bei pasiūlyta netiesinio f-3f interferometro schema impulso gaubtinės fazes fliuktuacijoms matuoti. / In this thesis we investigated and developed three- and four-wave interaction-based frequency conversion methods for ultrashort pulse generation in the ultraviolet (UV), near and mid-infrared (IR) spectral ranges. In particular, efficient generation of Nd:glass laser harmonics was demonstrated experimentally, through noncollinear four-wave difference-frequency mixing in isotropic media. Also, broadband optical parametric amplification in the UV was investigated theoretically and achieved experimentally. The results suggest, that pulses as short as 10 fs could be amplified. We have also developed two methods based on three- and four-wave mixing, that extend the tuning range of a commercial Ti:sapphire laser-NOPA system in the IR. The first method relies on four wave frequency down-conversion, and can achieve up to 20 μJ, sub-30-fs pulses tunable in the 1−1.5 μm range. The second method considers frequency conversion, based on difference frequency generation and optical parametric amplification in BBO crystals. The presented setup delivers two optical-cycle, carrier-envelope phase (CEP)-stable pulses at 2 μm. And finally, we demonstrated supercontinuum generation by filamentation of 20 fs pulses at 2 μm in wide-bandgap solids in the regime of anomalous group velocity dispersion. We also proposed the practical use of intrinsic third harmonic generation, for the CEP stability measurements.
48

Three and four wave parametric interactions for ultrashort pulse generation in the ultraviolet, near and mid-infrared spectral range / Trijų ir keturių bangų parametrinių sąveikų taikymas ultratrumpųjų impulsų generacijai ultravioletiniame, artimajame ir viduriniajame infraraudonajame spektro ruože

Darginavičius, Julius 25 September 2013 (has links)
In this thesis we investigated and developed three- and four-wave interaction-based frequency conversion methods for ultrashort pulse generation in the ultraviolet (UV), near and mid-infrared (IR) spectral ranges. In particular, efficient generation of Nd:glass laser harmonics was demonstrated experimentally, through noncollinear four-wave difference-frequency mixing in isotropic media. Also, broadband optical parametric amplification in the UV was investigated theoretically and achieved experimentally. The results suggest, that pulses as short as 10 fs could be amplified. We have also developed two methods based on three- and four-wave mixing, that extend the tuning range of a commercial Ti:sapphire laser-NOPA system in the IR. The first method relies on four wave frequency down-conversion, and can achieve up to 20 μJ, sub-30-fs pulses tunable in the 1−1.5 μm range. The second method considers frequency conversion, based on difference frequency generation and optical parametric amplification in BBO crystals. The presented setup delivers two optical-cycle, carrier-envelope phase (CEP)-stable pulses at 2 μm. And finally, we demonstrated supercontinuum generation by filamentation of 20 fs pulses at 2 μm in wide-bandgap solids in the regime of anomalous group velocity dispersion. We also proposed the practical use of intrinsic third harmonic generation, for the CEP stability measurements. / Pagrindinis šios disertacijos tikslas – sukurti efektyvius trijų ir keturių bangų sąveikomis paremtus metodus ultratrumpiesiems ultravioletinės (UV), artimosios bei vidurinės infraraudonosios (IR) spektro srities impulsams generuoti. Pademonstruota efektyvi Nd:stiklo lazerio harmonikų generacija nekolinearaus keturbangio skirtuminio dažnio žadinimo metodu izotropinėse terpėse. Disertacijoje taip pat eksperimentiškai ir teoriškai nagrinėjama galimybė stiprinti 10 fs trukmės UV impulsus. Pateikėme du metodus derinamo bangos ilgio IR impulsams generuoti naudojant komercinę Ti:safyro lazerio ir nekolinearaus optinio parametrinio stiprintuvo sistemą. Pirmasis metodas remiasi keturių bangų sąveikomis ir leidžia generuoti 20 μJ energijos, <30 fs trukmės impulsus 1−1.5 μm spektro ruože. Antrojo šaltinio veika remiasi skirtuminio dažnio generacijos bei optinio parametrinio stiprinimo sąveikomis BBO kristaluose. Sukurtas stiprintuvas, generuojantis dviejų optinių ciklų trukmės, stabilios gaubtinės fazės, 2 μm bangos ilgio impulsus ir pademonstruotas jo taikymas itin plataus spektro superkontinuumo generacijai plačios draustinės juostos kietojo kūno terpėse. Galiausiai, ištirta vienalaikė trečiosios harmonikos ir superkontinuumo generacija skaidriose dielektrinėse terpėse, bei pasiūlyta netiesinio f-3f interferometro schema impulso gaubtinės fazes fliuktuacijoms matuoti.
49

Studium dynamiky dynamiky magnetizace v GaMnAs pomocí ultrarychlé laserové spektroskopie / Investigation of magnetization dynamics in GaMnAs by ultrafast laser spectroscopy

Tesařová, Naďa January 2013 (has links)
i Abstract: This doctoral thesis is dedicated to the study of magnetization dynamics in ferromagnetic semiconductor (Ga,Mn)As using magneto-optical (MO) spectroscopy methods. The character of the magnetization dynamics after the impact of the laser pulse was investigated under different experimental conditions in an extensive set of optimized (Ga,Mn)As samples with Mn doping ranging from 1.5% to 14%. The thorough analysis of the measured MO signal enabled us to develop a new method that can be used to determine the laser pulse-induced real-space magnetization trajectory without any numerical modelling. Moreover, the investigation of the measured MO signals allowed us to determine the basic micromagnetic properties of (Ga,Mn)As, such as the magnetic anisotropy, the Gilbert damping or the spin stiffness. In addition to this, we found out that the light-induced magnetization precession can be caused by three distinct mechanisms - the sample heating due to the energy transfer from the laser pulses, the angular momentum transfer from the circularly polarized photons, and the influence of the non-equilibrium hole polarization induced by the relativistic spin-orbit interaction. The first of these mechanisms is rather well known but the two remaining ones, which are the optical analogues of the spin-transfer torque...
50

Diferencované pracovní listy při výuce fyziky na ZŠ / Differential worksheets by physics education at basic school

ŠTĚRBOVÁ, Lada January 2012 (has links)
My diploma thesis deals with the creation of differentiated worksheets for teaching physics on upper primary schools. It is focused specifically on optics and acoustics. The worksheets are used during the physics courses as the variety and supplement teaching in subsequent exercises at home, the development of selected key competencies, enhancing physical and logical thinking, the acquisition and consolidation of concepts and skills in the field of physics. Also in support of homework and even in extracurricular student experiments.

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