Compact Plasmonic Liquid Crystal Multiplexer–Demultiplexer for Optical Communication Systems

In this work, an efficient multiplexer-demultiplexer (MUX-DEMUX) based on silica on silicon (SiO₂/Si) waveguide is reported and numerically studied. The proposed design comprises two adjacent channels filled with E7 nematic liquid crystal (NLC) material, etched in the SiO₂ cladding. The NLC allows for the control of light propagation through the waveguide, under the effect of an applied electric field, owing to its electro-optic properties. Moreover, a gold (Au) nanowire is placed between the two NLC channels to reduce the device length of the suggested MUX-DEMUX. The full-vectorial finite-difference method and mode expansion method are employed to study the modal and propagation characteristics of the MUX-DEMUX, respectively. The simulation results demonstrate that the proposed multiplexer-demultiplexer exhibits a low insertion loss of 8 × 10⁻⁶ dB at a short device length of 1296 µm. Additionally, it achieves low crosstalk for the y-polarized mode, with values better than − 30 dB and − 37 dB at wavelengths of 1.55 µm and 1.3 µm, respectively.