Photonics and topology of liquid crystal dispersionsMur, Maruša (Avtor) Muševič, Igor (Mentor) optical switchstimulated emission depletion (STED)all-optical light controlwhispering gallery mode laserferromagnetic nematic dropletmagnetic field tuningtopological defect formationpassively driven nematicIn the thesis we examine three separate problems in liquid crystal dispersions. We study photonic properties of liquid crystal droplets and topological properties in a liquid crystal film. We design two different photonic micro-devices out of liquid crystal droplets, acting as microresonators, and investigate formation of topological defects in a liquid crystal film of a passively driven nematic. In the first topic we study stimulated emission depletion (STED) as a mechanism for all-optical control of light. We investigate STED effect in bulk liquid crystals and check how the depletion depends on liquid crystal phase and STED beam parameters. Later we use STED principle to create an all-optical switch, based on a dyed liquid crystal droplet. We produce tapered polymeric waveguides to couple light in and out of the droplet and show that STED can switch off whispering gallery mode resonances inside this microresonator, working on a sub-nanosecond timescale. In the second topic we study droplets, made of a ferromagnetic nematic liquid crystal, and their response to external magnetic field. When exposed to the field, the director configuration of a droplet acting as a microresonator gets distorted, which affects its optical properties. We show that whispering gallery mode lasing, supported by the microresonator, can be tuned by the applied field. The resonance wavelengths shift linearly with the magnetic field. The direction of the shift depends on whether the magnetic field is applied in the circulation plane of the whispering gallery modes or not. In the third topic we investigate a phenomenon of continuous topological defect creation and annihilation in a system of smectic liquid crystal, coming in contact with aqueous solution of 2-hydroxy-2-methylpropiophenone photoinitiator. We first research experimental geometry and characterize the system. Photoinitiator diffusion causes flows and liquid crystal melting, resulting in a passively driven nematic system. Later we analyze the movement of defects and the underlying flow. Finally we study defect formation and compare it to the theoretical proposal.20192019-03-22 07:45:03Doktorsko delo/naloga106861sl