Electrically tunable filter based on directional coupler with 1D photonic crystal arm infiltrated with smectic liquid crystal

We propose a concept for an electrically tunable optical filter based on a directional coupler consisting of a conventional silica glass waveguide and a 1D photonic-crystal waveguide formed as a stack of alternating Si and SiO₂ layers with an electroclinic smectic A* liquid crystal as a defect layer (core). We show theoretically that with a commercially available liquid crystal, BDH764E, tuning ranges as large as 80 nm in the 1.55 μm WDM band are possible under an applied electric field of less than 5 V/μm.