Circularly polarized light generated by photoexcitation of luminophores in glassy liquid-crystal films

Optical information processing, display and storage can be accomplished with linearly or circularly polarized light. In passive (non-emitting) devices, linear polarization can be produced by anisotropic absorption of light, whereas circular polarization has been attained by selective reflection of unpolarized light propagating through a chiral-nematic liquid-crystal film. Active (light-emitting) devices capable of polarized emission are also needed. In principle, optical and electronic excitation of materials containing uniaxially and helically arranged luminophores should produce linearly and circularly polarized emission, respectively. In practice, the former is easier to achieve and is therefore more technologically advanced. Here we report the generation of strongly circularly polarized photoluminescence from films of glass-forming chiral-nematic liquid crystals in which are embedded light-emitting dopants. This host material apparently induced alignment of the luminophores to a degree that produces almost pure circular polarization within the 400-420-nm wavelength band of the emitted light. We anticipate that composite films of this sort might find applications within photonic technology such as colour-image projection and stereoscopic displays.