Design and fabrication of an optical de-multiplexer

Optical multiplexers and de-multiplexers are fundamental components of every WDM system. A de-multiplexer takes in a combination of signals through a single input and outputs each individual signal on a separate output. This paper presents the design and fabrication of an optical de-multiplexer using a planar photonic crystal ((PC)-C-2) made of a triangular array of air holes perforated in a silicon substrate. The de-multiplexer operates in the commonly used 1550 nm wavelength, and is designed to be part of an Optical System on a Chip. The design consists of a (PC)-C-2 structure with a slab waveguide superimposed over it. The (PC)-C-2 structure has a normalized cylinder radius-to-pitch ratio r/a of 0.45 and a high dielectric material contrast epsilon(r) of 11.56. The planar structure provides lateral light confinement, while the slab waveguide restricts the light vertically by means of total internal reflection. We select our a/lambda ratio to be 0.42 at the operating frequency. This ratio yields values of 0.651 mum for the lattice constant a and 0.293 mum for the radius of the air holes.