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

TL;DR

This paper investigates the anomalous spectral shift in a Fabry-Pérot cavity filled with a chiral anisotropic medium, attributing it to geometric phase effects, and confirms the model through experiments with twisted nematic liquid crystals.

Contribution

It provides an analytical, numerical, and geometric explanation for the spectral shift, including the o-mode blue shift, in chiral anisotropic media inside a Fabry-Pérot cavity, supported by experimental validation.

Findings

Spectral shift explained by geometric phase contributions.

Measured o-mode blue shift in twisted nematic liquid crystal layer.

Experimental results confirm theoretical model validity.

Abstract

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.