The demultiplexer design described here is a planar diffraction grating that requires no add-on components or surface treatments to enhance reflectivity. By designing the light to reflect at a grazing angle to the grating surface, the design takes advantage of total internal reflection to eliminate the need for an add-on grating component or reflection enhancing coatings. In addition, this approach allows the grating to be placed anywhere on a substrate. The flexibility of photo definable technology allows us to design the grating with no aberrations at two design wavelengths. Wavelengths between these two design points show very little aberration. When implemented as a multimode structure the resolution is degraded somewhat. Simulation results show the performance potential of this design.