Photochemical switching between colloidal photonic crystals at the nematic-air interface.
A direct observation of the photochemical switching between colloidal crystals with different lattice constants in a liquid-crystal (LC) emulsion is reported. Glycerol droplets introduced in a nematic liquid crystal form two-dimensional hexagonal colloidal crystal at the nematic-air interface with a lattice constant depending on the surface tension sigmaLCA. We dope an azobenzene derivative into the LC emulsion to modulate the colloidal structures by using cis-trans photoisomerization of the doped dye. The photoisomerization changes sigmaLCA and the lattice constant of colloidal crystals with a relaxation time T approximately 10s . A simple theoretical description, which qualitatively agrees with experimental results, has been proposed. Possible applications in infrared range photonic crystals are discussed. The number of different kinds of dyes N set the number of different possible photonic crystals as 2N, which may be transformed one into another by corresponding 2N light beams inducing cis-trans photoisomerization of the doped dyes.
Lev
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Bogolyubov Institute of Theoretical Physics, NAS Ukraine, Metrologichna 14-b, Kyiv 03143, Ukraine.
Chernyshuk
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SB
Yamamoto
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T
Yamamoto
J
J
Yokoyama
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H