Patent ID: 7386206

Claim:
An apparatus comprising: a substrate; a slab waveguide formed on the substrate and having a terminal which operates as both an input and output to the apparatus; channel waveguides of differing lengths formed on the substrate and extending to an end face of the substrate with output ends of the channel waveguides arranged in a straight line, light input to the slab waveguide via the terminal traveling through the slab waveguide and then being input to the channel waveguides, wherein a wavelength division multiplexed (WDM) light is input to the slab waveguide via the terminal to thereby travel through the slab waveguide and be input to the channel waveguides of differing lengths, the channel waveguides of differing lengths having differences in optical path lengths, respectively, so that light at different wavelengths in the WDM light is angularly dispersed from the end face of the substrate in different directions, respectively, in accordance with wavelength; a focusing device focusing the angularly dispersed lights at different wavelengths at different positions, respectively; and a reflecting device reflecting at least some of the focused lights so that said reflected at least some of the focused lights travel back through channel waveguides of the channel waveguides and then through the slab waveguide to thereby be output through the terminal, wherein the terminal and the output ends of the channel waveguides form 90° angles.