12 September 2005 Director fields of nematic liquid crystals in tunable photonic crystals
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Variations of the refractive index can be utilized in order to shift the stop band in photonic crystals. Here, two- and three-dimensional structures made of macroporous silicon were filled with liquid crystals. Optical investigations in the infrared wavelength range indicate temperature-induced spectral shifts of the edges of stopbands. In addition, the defect modes corresponding to microcavities within the periodic structure can be thermally controlled. Investigations of the director field within the pores by means of 2H-NMR and confocal microscopy indicate that both parallel and escaped radial director fields can appear, depending on the surface treatment of the substrates. In cylindrical pores with a periodic modulation of the pore diameter, the escaped radial director field is modified thereby showing a regular array of disclination rings.
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Heinz-Siegfried Kitzerow, Heinz-Siegfried Kitzerow, Guido Mertens, Guido Mertens, Heinrich Matthias, Heinrich Matthias, Heinrich Marsmann, Heinrich Marsmann, Ralf B. Wehrspohn, Ralf B. Wehrspohn, Sven Matthias, Sven Matthias, Ulrich Goesele, Ulrich Goesele, Stefan Frey, Stefan Frey, Helmut Foell, Helmut Foell, } "Director fields of nematic liquid crystals in tunable photonic crystals", Proc. SPIE 5926, Tuning the Optical Response of Photonic Bandgap Structures II, 592605 (12 September 2005); doi: 10.1117/12.616456; https://doi.org/10.1117/12.616456

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