Multiplexing and demultiplexing with photonic crystals

We investigate the propagation of electromagnetic waves in two-dimensional doped photonic crystals. We numerically demonstrate how photonic crystals may be used to multiplex and demultiplex optical signals. By inserting three different kinds of defect, we are able to design three distinct waveguides inside the same structure. Two waveguides geometrically separate, in two paths, the optical signal for two frequency ranges. The third waveguide mixes the waves in order to multiplex both frequency ranges. The demultiplexing is performed by executing the same operations but in the opposite order.