Liquid-Crystal Filters for Visible WDM Channels over Polymer Optical Fibres
Résumé
his paper describes the development of discrete optical filters operating in the visible spectra aiming the Wavelength-Division Multiplexing (WDM) links over Poly-Methyl-Methacrylate (PMMA) polymer optical fibres (POFs). The fabrication of notch and dichroic filters was carried out using a nematic liquid crystal (LC) doped with appropriate chiral dopant. In order to have the reflection of above 80% for the desired wavelength we used approximately 20 layers of cholesteric LC in a planar Grandjean texture. In order to operate the device for any given input polarisation, the cholesteric liquid crystal (CLC) with left handed helix will reflect left circularly polarised light while the right handed helix will reflect the right handed circularly polarised light.