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Plasmonic antennas for high wavelengths
Beneš, Adam ; Chvátal, Lukáš (referee) ; Křápek, Vlastimil (advisor)
Tato diplomová práce se zabývá vlastnostmi plazmonických antén v oblasti vysokých vlnových délek. Důraz je kladen na popis rezonančních vlastností jednotlivých antén i antén uspořádaných do periodických polí. Těžiště práce spočívá v počítačovém modelování navýšení magnetického pole v blízkosti antén, které lze využít ve vysokofrekvenční elektronové paramagnetické rezonanci (HFEPR) k zesílení měřeného signálu. Autor se zabývá kvantifikací zesílení v anténách s odlišnou geometrií a navrhuje i geometrii vlastní. Značná část práce se také věnuje snaze rozlišit příspěvky k navýšení magnetického pole od různých zdrojů při měření HFEPR v uspořádání s dvojitou transmisí záření.
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Quantum description of superradiance of emitters with plasmon-mediated interaction
Olivíková, Gabriela ; Chvátal, Lukáš (referee) ; Křápek, Vlastimil (advisor)
Superradiance is an enhanced decay of an excited system of emitters resulting from their mutual coupling. This thesis is focused on superradiance of the emitters coupled via their interaction with a plasmonic nanoparticle. So-called plasmon-mediated superradiance results in even stronger enhancement of the decay rate as the nanoparticle serves as an additional decay chanel. We have developed a quantum model of the system of emitters coupled to a plasmonic nanoparticle, which allows us to differentiate between a pure dephasing and decay processes. We show that the pure dephasing can destroy the cooperative effect leading to superradiance. Furthermore, we have studied how the direct mutual coupling between emitters affects time evolution of the system in dependence on its configuration, and we show conditions when a decay of the system is dramatically decreased by direct coupling.
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Plasmonic antennas for high wavelengths
Beneš, Adam ; Chvátal, Lukáš (referee) ; Křápek, Vlastimil (advisor)
Tato diplomová práce se zabývá vlastnostmi plazmonických antén v oblasti vysokých vlnových délek. Důraz je kladen na popis rezonančních vlastností jednotlivých antén i antén uspořádaných do periodických polí. Těžiště práce spočívá v počítačovém modelování navýšení magnetického pole v blízkosti antén, které lze využít ve vysokofrekvenční elektronové paramagnetické rezonanci (HFEPR) k zesílení měřeného signálu. Autor se zabývá kvantifikací zesílení v anténách s odlišnou geometrií a navrhuje i geometrii vlastní. Značná část práce se také věnuje snaze rozlišit příspěvky k navýšení magnetického pole od různých zdrojů při měření HFEPR v uspořádání s dvojitou transmisí záření.
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A case report of physiotherapeutic care of a patient after surgery for subtrochanteric chondrosarcoma
Chvátal, Lukáš ; Vomáčková, Helena (advisor) ; Kaucká, Eva (referee)
Title of bachelor's thesis: A case report of physiotherapeutic care of a patient after surgery for subtrochanteric chondrosarcoma. Objectives: The objective of this thesis is a collection of theoretical and practical knowledge about chondrosarcoma and their application to a case study of patient, who is two years after the operation of chondrosarcoma on the proximal femur, where they have used a graft from the fibula bone on the right leg. Summary: The bachelor's thesis is split into two sections: general section and a specific section. The general section describes the pathophysiology of overall tumours and then in each part the topic is narrowed down to just chondrosarcomas. It gives information about the epidemiology, etiologic, classification and clinical picture of a patient with chondrosarcoma. Also it describes a way to prevent, cure and a following rehabilitation. The specific section contains a case study of a patient, who suffered this illness and it has been two years after the operation. The sections include the input and output kinesiology analysis, short-term and long-term plan of a therapy, the design of the therapy, the description of course of individual therapeutic units and a final evaluation of the effect of the therapy. Conclusion: The patient has successfully got rid of acute...
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Optical binding of polystyrene particles in tractor beam
Damková, Jana ; Chvátal, Lukáš ; Oulehla, Jindřich ; Ježek, Jan ; Brzobohatý, Oto ; Zemánek, Pavel
The motion of a particle illuminated by a laser beam is usually driven by the photon flow due\nto the radiation pressure and therefore for particle trapping, one has to employ gradient forces. But in a tractor beam, objects are illuminated by the uniform light intensity and even so they can be pulled against the beam propagation. There have been developed several techniques how to create such a tractor beam. In our case, the tractor beam is created by two identical Gaussian beams that interfere under the defined angle. It creates the\nstanding wave, where in the transversal plane the particle is trapped by means of the gradient\nforce, but in the total beam propagation direction, the particle manipulation is driven by the non-conservative force. It is remarkable that this force can for the specific combinations of\nparameters pull the micro-particle against the beam propagation. This kind of behavior is\nbecause of the particle scattering where the majority of the incident photons is scattered in the forward direction and, based on the principle of action and reaction, the transfer of\nmomentum leads to a backward movement of the object. The pushing and pulling force is\nsensitive to the polarization of the laser beam, its incident angle and the particle size so this\ntechnique can be used for example for sorting of objects of different sizes.
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Quantum description of superradiance of emitters with plasmon-mediated interaction
Olivíková, Gabriela ; Chvátal, Lukáš (referee) ; Křápek, Vlastimil (advisor)
Superradiance is an enhanced decay of an excited system of emitters resulting from their mutual coupling. This thesis is focused on superradiance of the emitters coupled via their interaction with a plasmonic nanoparticle. So-called plasmon-mediated superradiance results in even stronger enhancement of the decay rate as the nanoparticle serves as an additional decay chanel. We have developed a quantum model of the system of emitters coupled to a plasmonic nanoparticle, which allows us to differentiate between a pure dephasing and decay processes. We show that the pure dephasing can destroy the cooperative effect leading to superradiance. Furthermore, we have studied how the direct mutual coupling between emitters affects time evolution of the system in dependence on its configuration, and we show conditions when a decay of the system is dramatically decreased by direct coupling.
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Golden nanoparticle in optical tweezers: influence of shape and orientation on optical trapping
Šiler, Martin ; Brzobohatý, Oto ; Chvátal, Lukáš ; Karásek, Vítězslav ; Paták, Aleš ; Pokorná, Zuzana ; Mika, Filip ; Zemánek, Pavel
Noble metal nanoparticles (NPs) have attracted increased attention in recent years due to various applications of resonant collective oscillations of free electrons excited with light (plasmon resonance). In contrast to bulk metal materials, where this plasmon resonance frequency depends only on the free electron number density, the optical response of gold and silver NPs can be tuned over the visible and near-infrared spectral region by the size and shape of the NP. Precise and remote placement and orientation of NPs inside cells or tissue would provide another degree of control for these applications. A single focused laser beam – optical tweezers – represents the most frequently used arrangement which provides threedimensional (3D) contact-less manipulation with dielectric objects or living cells ranging in size from tens of nanometers to tens of micrometers. It was believed that larger metal NPs behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, recently several groups have reported successful optical trapping of gold and silver particles as large as 250 nm. We\noffer an explanation based on the fact that metal nanoparticles naturally occur in various nonspherical\nshapes, and their optical properties differ significantly due to changes in localized plasmon excitation.
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From the mere pushing to sorting of microparticles and assembly of microrobots by light
Zemánek, Pavel ; Arzola, Alejandro V. ; Brzobohatý, Oto ; Chvátal, Lukáš ; Jákl, Petr ; Kaňka, Jan ; Karásek, Vítězslav ; Šerý, Mojmír ; Šiler, Martin
We demonstrate the recent progress in the field of optical micromanipulation. We start with the classical applications of solar sail propelled by the radiation pressure and approach the recent ones dealing with optical tractor beams, optical binding and sorting of microobjects. The pioneering attempts to assemble a microrobot by light is presented.
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