LC Physics

Session 1A: LC Physics
Monday, Feb. 13, 2017  14:20-15:40
Chair: Jan P. F. Lagerwall, University of Luxembourg, Luxembourg
Room: Lecture Hall III
15:10 - 15:25 Paper No.  2017-MON-S0101-O001
Hideo Takezoe
Photomanipulation of the anchoring strength using spontaneously adsorbed layer of azo dendrimers

In this study, we comprehensively explored the photoinduced anchoring transition in a nematic liquid crystal containing the azo dendrimers. Because the azo dendrimer in the trans-isomer state spontaneously adsorbed at substrate surfaces in a polar fashion, which was confirmed by optical second harmonic generation (SHG), a homeotropic orientation was established at the first stage. Ultraviolet (UV) light irradiation diminished the SHG intensity due to photoisomerization, resulting in a planar orientation. The monotonic decrease of the effective scalar order parameter with increasing UV light intensity was found by polarized attenuated total reflection infrared (ATR-IR) spectroscopy. The variations of anchoring strength and extrapolation length were evaluated by observing the Freedericksz transition as a function of UV light intensity under a certain visible (VIS) light intensity. Such photoinduced variations were analyzed as a variation of anchoring strength depending on the trans/cis ratio at the surfaces based on a modified Rapini-Papoular model.

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15:25 - 15:40 Paper No.  2017-MON-S0101-O002
Kuo-Ping Chen
Tunable Metasurfaces with Liquid Crystals

Planar photonics, like metasurfaces and nanoantennas, has caught immense attention because of the ability of controlling the phase and polarization of light. The tunability of metasurfaces system could be realized by combining with liquid crystals. In this work, several novel devices, like tunable nanoantennas arrays with color, diffraction control of binary gratings metasurfaces, and optical Tamm states would be presented. First, by changing different dimensions of nanoantennas, the anchoring energy of liquid crystal could be adjusted in nanoscale. The different shapes of nanoantennas show the difference in color or monotone change when applying different voltages. Second, the diffraction ratio of metasurface could be controlled by nematic liquid crystal by controlling the polarization direction by applying voltages. Third, optical Tamm states could be realized and adjustable by combining liquid photonic crystal with metasurface. All of those ideas are realized in both modeling and experimental, which could give a great impact to the field of future application in tunable metasurfaces.

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