Photonic crystal-based dual-band demultiplexers on silicon materials

This investigation presents a novel design of dual-band demultiplexers based on a periodic hexagonal lattice of holes or rods on silicon materials. The demultiplexing function can be applied by coupling between two defect waveguides at one wavelength with no coupling then at another wavelength. Appropriately choosing the radius and number of separated rows yields a broad bandwidth for one range of wavelengths. Two designs that use rods or holes to generate photonic crystals are realized. An analysis based on finite-difference time-domain (FDTD) and plane wave expansion (PWE) methods demonstrates that a 1.3/1.55 μm dual-band wavelength demultiplexer can have a very low insertion loss and high isolation ratio.