Geometric phase and o-mode blue shift in a chiral anisotropic medium inside a Fabry-P\'erot cavity

Anomalous spectral shift of transmission peaks is observed in a Fabry--P\'erot 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--Poincar\'e rolling cone method. The $o$-mode blue shift is measured for a 4-methoxybenzylidene-4'-$n$-butylaniline twisted--nematic layer inside the Fabry--P\'erot 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.Comment: the text is available both in English (Timofeev2015en.tex) and in Russian (download: other formats - source - Timofeev2015ru.tex, Timofeev2015rus.pdf

Hinton, Deane R.

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 helix 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 it is only anisotropy of magnetic permittivity that can ultimately cancel this coupling. These two couplings being equal results 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

ELECTRO-OPTICAL RESPONSE OF POLYMER DISPERSED NEMATIC WITH AXIAL-BIPOLAR DIRECTOR CONFIGURATION

The results of the study of the electro-optical response of polymer dispersed liquid crystal films in which the polymer sets conical boundary conditions are presented. It is shown that such films have a high light transmittance T, low control electrical fields and large values of the contrast ratio

Polarization characteristics of light passed through a cholesteric layer with tangential-conical boundary conditions

The present work is devoted to the investigation of the polarization characteristics of light passed through the cholesteric layer with tangential-conical boundary conditions

New monomers for (bi)pyridine-containing polymers

Received: 09.09.2020. Accepted: 20.12.2020. Published:30.12.2020.Convenient methods for the synthesis of three monomers based on functionalized (bi)pyridines with using “1,2,4‑triaizine” methodology have been developed.This work was supported by the Russian Foundation for Basic Research (Grant #19‑53‑55002) and Grants Council of the President of the Russian Federation (no. NSh-2700.2020.3)

Electro-optical response of PDLC films with conical boundary conditions

Polymer dispersed liquid crystals (PDLC) are the liquid crystal (LC) droplets dispersed in polymer matrix. Optical properties of such composite materials depend on the orientational structure inside droplets which, in turn, depends on the boundary conditions at LC-polymer interface. For instance, the bipolar director configuration with two point defects at the opposite droplet's poles is formed within droplets at tangential surface anchoring. An electric field applied to this PDLC film causes the transformation of orientational structure and reorientation of bipolar droplet axis along the field. In the result, PDLC film can be switched from a ight-scattering state to transparent one

Two mutually complementary synthetic approaches towards 3‑substituted 3,4‑disubstituted and 1-(2‑pyridyl)-substituted isoquinolines

Received: 08.09.2018. Accepted: 19.10.2018. Published: 31.10.2018.Two mutually complementary synthetic approaches towards 3- and 3,4‑disubstituted 1-(2‑pyridyl) isoquinolines were studied. The aryne-based method was successfully used for the obtaining of the corresponding the 3‑cyano-1-(2‑pyridyl) isoquinolines in one step / pot reaction, while it is unacceptable for the obtaining of other 1-(2‑pyridyl)isoquinolines. The enamine-based approach was successfully applied for the synthesis of other 1-(2‑pyridyl)isoquinolines, while it was unacceptable for the obtaining of 3‑cyano-1-(2‑pyridyl)isoquinolines.This work was supported by the Russian Science Foundation (Reference № 18‑13‑00365)