Dresden 2017 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 16: Crystallography - Poster Session (KR with DF)

DF 16.4: Poster

Mittwoch, 22. März 2017, 18:00–20:00, P4

Detection of pressure and density waves (acustic waves) in liquid crystal near the phase transition temperature by gold nano particle — •Ricardo Rose, Andre Heber und Frank Cichos — Universität Leipzig Fakultät für Physik und Geowissenschaften, Leipzig, Germany

Recent studies have shown, that the intensity of a polarized laser beam can be modulated by a second heating laser beam, which excites plasmons on gold nanoparticles (AuNp) positioned in liquid crystal (LC). The exited AuNp dissipate the energy as heat into the LC. If the LC is near below the phase transition point from nematic phase to isotropic phase, the dissipated heat will suffice to build an isotropic bubble around the AuNp. The size of the bubble can be controlled by the amount of supplied energy. While the polarization within the nematic phase is rotated due to different refractive indices for the ordinary and extraordinary axis similar to a λ / 2 - plate, the polarization will be conserved within the isotropic phase. If an analyzer is placed behind the LC, the intensity of the probe laser beam can be modulated by the optical path length within the nematic phase and their disturbance within the isotropic bubble around the laser heated AuNp. In this study we investigate, if the deformation of the isotropic bubble by acoustical waves and the linked modulation of the probe laser beam intensity at constant, unmodulated power of the heating laser will be clearly detectable, while the ambient temperature is near the phase transition temperature. If that can be proven, we will able to design a microphone at nano size.