Optical router with nearly ideal performance and increased number of channels

Abstract

An optimized planar optical router consisting of two stages performing stationary imaging between an input waveguide and a set of output waveguides has advantages of reduced size, larger number of channels and minimal loss variation in each passband. The new router is an optimized M×N imaging arrangement including two waveguide gratings and n waveguide lenses connected between the principal zones of the two gratings. The largest values of N are realized by using a combination of two techniques that increase N without increasing the size of the two gratings. One technique increases N for a given number n of lenses and, the other, increases n. In one embodiment, each lens produces a periodic sequence of passbands, all transmitted from a particular input waveguide to the same output waveguide, whereas, in a second embodiment, the above passbands are transmitted to different output waveguides. In both cases, the loss caused by secondary images is substantially reduced by including secondary lenses.