Patent ID: 7076135
Filing Date: 2006-07-11
Classification: G02B

Abstract:
1. An optical module comprising: an under cladding having a flat shape as a whole; a first core which has a quadrangular cross section and is placed on said under cladding; a second core placed on a terminal end portion of said first core and completely covering said terminal end portion; and an over cladding placed in a region including the terminal end portion of said first core and said second core placed on the terminal end portion of said first core, wherein said under cladding and said first core placed thereon constitute a first optical waveguide, said under cladding, the terminal end portion of said first core placed on said under cladding, said second core placed thereon, and said over cladding placed on and around said second core constitute a mode field size conversion portion, said under cladding, said second core placed on said under cladding, and said over cladding placed on and around said second core constitute a second optical waveguide, said first core is made of silicon, said second core is made of a material higher in refractive index than said under cladding and lower in refractive index than silicon of said first core and the terminal end portion, said first and second cores differ in cross-sectional shape, a refractive index of said over cladding is higher than that of said under cladding, and a specific refractive index difference between said second core and said under cladding is larger than that between said second core and said over cladding.