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Optical levitation of dielectric objects in an external electric field
Zemánková, Tereza ; Flajšmanová,, Jana (referee) ; Svak, Vojtěch (advisor)
The bachelor's thesis deals with the optical levitation of a dielectric microparticle in vacuum and its displacement by an external electric field. The theoretical part mathematically describes the laser beam, in which particles are stably trapped. Subsequently, the principles of optical trapping, particle confinement and the most common experimental geometries of optical traps, e.g. counter-propagating beams, optical levitation and optical tweezers, are introduced. Because the trapped particle behaves very similarly to a harmonic oscillator excited by white noise, at the end of the theoretical part there are presented the equations of motion of the particle and their solutions for various cases, including Langevin equation of motion. The experimental part describes two experimental setups, in the assembly of which I participated. In the last part results of two main experiments are presented - displacement of the trapped particle by an external electric field, including determination of its charge, driving the particle by controlled white noise and determination of the effective temperature of stochastic motion of the particle.
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Dynamics of Microparticles Optically Trapped in Vacuum
Svak, Vojtěch ; Čižmár, Tomáš (referee) ; Marago, Onofrio (referee) ; Brzobohatý, Oto (advisor)
Mikročástice levitující ve vakuu pouze za pomoci silových účinků světla představuje mechanický systém, který je extrémně dobře izolován od okolních a jeho zdrojů šumu. Tato unikátní vlastnost poskytuje tomuto systému nevídanou citlivost na změny okolních podmínek. V předkládané práci je popsáno technické řešení experimentální sestavy pro optické chytání ve vakuu, která byla realizována v laboratořích skupiny levitační fotoniky Ústavu přístrojové techniky AVČR v Brně. Dále je prezentována experimentální studie dynamiky částice zachycené v kruhově polarizovaném optickém poli, které generuje nekonzervativní složku pole optické síly. Následuje experimentální pozorování a popis dynamiky dvou opticky vázaných mikročástic ve volném prostoru ve vakuu, což je konfigurace, která nebyla nikdypředtím realizována. Závěrem je představena zcela originální metoda pro odhad silového pole optické pasti založená na analýze stochastické trajektorie zachycené částice.
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Optical levitation of dielectric objects in an external electric field
Zemánková, Tereza ; Flajšmanová,, Jana (referee) ; Svak, Vojtěch (advisor)
The bachelor's thesis deals with the optical levitation of a dielectric microparticle in vacuum and its displacement by an external electric field. The theoretical part mathematically describes the laser beam, in which particles are stably trapped. Subsequently, the principles of optical trapping, particle confinement and the most common experimental geometries of optical traps, e.g. counter-propagating beams, optical levitation and optical tweezers, are introduced. Because the trapped particle behaves very similarly to a harmonic oscillator excited by white noise, at the end of the theoretical part there are presented the equations of motion of the particle and their solutions for various cases, including Langevin equation of motion. The experimental part describes two experimental setups, in the assembly of which I participated. In the last part results of two main experiments are presented - displacement of the trapped particle by an external electric field, including determination of its charge, driving the particle by controlled white noise and determination of the effective temperature of stochastic motion of the particle.
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Orbital motion from optical spin: the extraordinary momentum of circularly polarized light beams
Svak, Vojtěch ; Brzobohatý, Oto ; Šiler, Martin ; Jákl, Petr ; Zemánek, Pavel ; Simpson, Stephen Hugh
We provide a vivid demonstration of the mechanical effect of transverse spin momentum in an\noptical beam in free space. This component of the Poynting momentum was previously thought\nto be virtual, and unmeasurable. Here, its effect is revealed in the inertial motion of a probe\nparticle in a circularly polarized Gaussian trap, in vacuum. Transverse spin forces combine with\nthermal fluctuations to induce a striking range of non-equilibrium phenomena. With increasing\nbeam power we observe (i) growing departures from energy equipartition, (ii) the formation of\ncoherent, thermally excited orbits and, ultimately, (iii) the ejection of the particle from the trap.\nOur results complement and corroborate recent measurements of spin momentum in evanescent\nwaves, and extend them to a new geometry, in free space. In doing so, we exhibit fundamental,\ngeneric features of the mechanical interaction of circularly polarized light with matter. The work\nalso shows how observations of the under-damped motion of probe particles can provide detailed\ninformation about the nature and morphology of momentum flows in arbitrarily structured light\nfields as well as providing a test bed for elementary non-equilibrium statistical mechanics.
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