The design of a complete demultiplexer based on the k-vector superprism in a 1-D slab photonic crystal is proposed. This design scales to resolve 32 channels spaced by 0.8 nm (100 GHz) in the C band for a dense wavelength division multiplexing system. It is shown that a prism area of 0.017 mm;2 is sufficient for the required wavelength resolution using typical silicon-on-insulator technology and that the total chip size would be 4x3 mm;2. In order to achieve this, the modest angular dispersion of a 1-D slab photonic crystal is enhanced by considerably expanding the input beam through the superprism region and employing etched mirrors to collimate and focus the light into and out of the superprism. The plane wave expansion method is used to obtain the wave vector diagram and from this we develop design equations based on conventional ray tracing. We then present an optimization approach which minimizes the prism area whilst maintaining the necessary dispersion. Finally the non-uniformity of phase velocity dispersion across the desired spectral window is addressed.