Abstract
The aim of this paper was to propose and design an all optical four-channel demultiplexer using two-dimensional photonic crystals. To do so a resonant cavity was created by reducing the radius of the two adjacent rods. The radius of these defect rods was about 85 nm. The resonant cavity has a resonant mode at 1,557 nm. Then by using four resonant cavities with different radius values a four-channel optical demultiplexer was designed. The demultiplexer has four optical channels at λ1=1,537 nm, λ2=1,546 nm, λ3=1,553 nm and λ4=1,560 nm.