Optical multi-demultiplexer

An optical multi-demultiplexer comprising:

• a substrate;
• input waveguides formed on the substrate;
• a channel waveguide array including a plurality of curved waveguides arranged such that optical path lengths of adjacent ones of the curved waveguides are gradually increased from an inside toward an outside of a curved configuration of the curved waveguides;
• output waveguides formed on the substrate;
• a first slab waveguide formed between the input waveguides and the channel waveguide array;
• a second slab waveguide formed between the channel waveguide array and the output waveguides, and
• a different refractive index region formed at a position close to the channel waveguide array within the second slab waveguide, the different refractive index region having a higher refractive index than a core of the second slab waveguide, the different refractive index region extending in a direction in which the waveguides of the channel waveguide array are arranged, and
• the different refractive index region having a reverse-tapered shape increasing in width from both side portions toward a central portion of the second slab waveguide.

An optical multi-demultiplexer comprising:

• a substrate;
• input waveguides formed on the substrate;
• a channel waveguide array including a plurality of curved waveguides arranged such that optical path lengths of adjacent ones of the curved waveguides are gradually increased from an inside toward an outside of a curved configuration of the curved waveguides;
• output waveguides formed on the substrate;
• a first slab waveguide formed between the input waveguides and the channel waveguide array;
• a second slab waveguide formed between the channel waveguide array and the output waveguides, and
• a different refractive index region formed at a position close to the channel waveguide array within the second slab waveguide, the different refractive index region having a higher refractive index than a core of the second slab waveguide, the different refractive index region extending in a direction in which the waveguides of the channel waveguide array are arranged,
• wherein the different refractive index region comprises a pair of peninsular different refractive index regions projecting from both sides of the second slab waveguide toward a central portion of the second slab waveguide.