1 x 8 Supergrating wavelength-division demultiplexer in a silica planar waveguide

Wavelength-division demultiplexing by superimposed gratings (supergrating) in a planar waveguide is modeled, accounting for intergrating coupling, and a theoretical decoupling criterion that serves as a guideline for practical design is presented. Superimposed gratings were formed by direct photoinscription in a photosensitive silica planar waveguide, which is a promising method for practical optical circuit applications. A 1x8 channel wavelength-division multiplexer is demonstrated experimentally as a proof-of-concept study. The effects on experimental performance of wavelength-selectivity broadening and finite photosensitive index-modulation depth are discussed.