Patent ID: 6898349

Claim:
An optical multi-demultiplexer comprising: an input waveguide to which wavelength division multiple signals are applied; a plurality of output waveguides for demultiplexing and outputting the wavelength division multiple signals; an arrayed waveguide provided between the input waveguide and the output waveguides and including a plurality of channel waveguides having different waveguide lengths; an input slab waveguide formed between the input waveguide and the arrayed waveguide, said input slab waveguide including a core layer and a clad layer and having axes extending from the input waveguide to the channel waveguides; an output slab waveguide formed between the arrayed waveguide and the output waveguides, said output slab waveguide including a core layer and a clad layer and having axes extending from the output waveguides to the channel waveguides, and two or more island regions having a refractive index different from that of the core layers of the input and output slab waveguides and provided in at least one of the slab waveguides and situated in positions associated with the channel waveguides of the arrayed waveguide and is an elongated one extending along one of said axes; wherein the refractive index of said island regions is lower than that of the core layer around the island regions and said island regions are formed integrally with the clad layer of the slab waveguide.