This paper proposes a novel wavelength division multiplexer (WDM) demultiplexer design for dense WDM networks. The proposed demultiplexer consists of rectangular shaped periodic frequency filters connected in series. These rectangular filters can be formed with an apodized one-dimensional (1-D) photonic crystal structure on a ridged semiconductor waveguide. A design example is given for such filters. In such designs, we can use a moderate refractive index contrast, in discrete groups of many layers, to achieve the same stop-band width that we would get with a large contrast. Apart from being compact in size, to demultiplex an arbitrary wavelength from N wavelengths, only \log_2 N switches and filter stages are required. This type of filter has a large potential to be used in integrated photonic implementation and packet switched dense WDM applications.
Cedric F. Lam, Rutger B. Vrijen, Patty P. L. Chang-Chien, Daniel F. Sievenpiper, and Eli Yablonovitch, "A Tunable Wavelength Demultiplexer Using Logarithmic Filter Chains," J. Lightwave Technol. 16, 1657- (1998)