Browsing by Author "Vetrov, Stepan Ya."

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Chiral Optical Tamm States: Temporal Coupled-Mode Theory
(2017-04-01)
Timofeev, Ivan V.
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Pankin, Pavel S.
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Vetrov, Stepan Ya.
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Arkhipkin, Vasily G.
;
Lee, Wei
The chiral optical Tamm state (COTS) is a special localized state at the interface of a handedness-preserving mirror and a structurally chiral medium such as a cholesteric liquid crystal or a chiral sculptured thin film. The spectral behavior of COTS, observed as reflection resonances, is described by the temporal coupled-mode theory. Mode coupling is different for two circular light polarizations because COTS has a helical structure replicating that of the cholesteric. The mode coupling for co-handed circularly polarized light exponentially attenuates with the cholesteric layer thickness since the COTS frequency falls into the stop band. Cross-handed circularly polarized light freely goes through the cholesteric layer and can excite COTS when reflected from the handedness-preserving mirror. The coupling in this case is proportional to anisotropy of the cholesteric and theoretically only anisotropy in magnetic permittivity can ultimately cancel this coupling. These two couplings being equal result in a polarization crossover (the Kopp-Genack effect) for which a linear polarization is optimal to excite COTS. The corresponding cholesteric thickness and scattering matrix for COTS are generally described by simple expressions.
Geometric phase and o-mode blueshift in a chiral anisotropic medium inside a Fabry-Perot cavity
(2015-11-24)
Timofeev, Ivan V.
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Gunyakov, Vladimir A.
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Sutormin, Vitaly S.
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Myslivets, Sergey A.
;
Arkhipkin, Vasily G.
Anomalous spectral shift of transmission peaks is observed in a Fabry-Perot cavity filled with a chiral anisotropic medium. The effective refractive index value resides out of the interval between the ordinary and the extraordinary refractive indices. The spectral shift is explained by contribution of a geometric phase. The problem is solved analytically using the approximate Jones matrix method, numerically using the accurate Berreman method, and geometrically using the generalized Mauguin-Poincare rolling cone method. The o-mode blueshift is measured for a 4-methoxybenzylidene-4'-n-butylaniline twisted-nematic layer inside the Fabry-Perot cavity. The twist is electrically induced due to the homeoplanar-twisted configuration transition in an ionic-surfactant-doped liquid crystal layer. Experimental evidence confirms the validity of the theoretical model.