Patent ID: 7471864

Claim:
An integrated optical waveguide comprising: a first optical waveguiding region having a refractive index of N 1 ; a second optical waveguiding region having a refractive index of N 2 different from that of said first optical waveguiding region, wherein an incident angle θ 1 at an interface surface between said first and second optical waveguiding regions with respect to the waveguide direction of said first optical waveguiding region satisfies the following relationships: 4θ B1 /5≦θ 1 ≦θ B1 +2/3(θ A1 -θ B1 ) θ B1 =tan −1 (N 2 /N 1 ) θ A1 =sin −1 (N 2 /N 1 ); and a third optical waveguiding region having a refractive index of N 3 different from that of said second optical waveguiding region, wherein an interface surface between said second and third optical waveguiding regions is inclined with respect to a refraction direction through the interface surface between said first and second optical waveguiding regions and wherein the third optical waveguiding region is disposed such that a refraction direction through the interface surface between the second and third optical waveguiding regions is in line with the waveguide direction of said third optical waveguiding region.