On the circular polarization of fluorescence from dyes dissolved in chiralnematic liquid crystals

The sense of circular polarization of the fluorescence from dyes dissolved in chiral nematic liquid crystals (CNLCs) with a photonic stopband overlapp ing the dye emission ('resonance regime') displays a peculiar reversal as a function of wavelength, which so far is not satisfactorily explained. We s ystematically study this phenomenon and show that theories based on the gue st/host alignment of the fluorescent dye in the CNLC matrix are not adequat e in the resonance regime. We instead propose a consistent explanation of s ign reversal based on the description of CNLCs as one-dimensional (1D) phot onic crystals. (C) 2001 Elsevier Science B.V. All rights reserved.