Abstract: An optical mode-size converter is presented, which includes a guiding portion, a first strip with a first refractive index, and a second strip with a second refractive index. The first refractive index and the second refractive index are higher than a refractive index of the guiding portion, and a section of the first strip and a section of the second strip overlap to form an evanescent coupling region. The optical mode-size converter further comprises a coupling layer disposed between the first strip and the second strip within the evanescent coupling region, wherein the refractive index of the coupling layer is larger than the refractive index of the guiding portion and smaller than the first refractive index and the second refractive index.

Abstract: An optical mode-size converter is presented, which includes a guiding portion, wherein at least a portion of the guiding portion extends between a first end and a second end along a first path, a first strip with a first refractive index, and a second strip with a second refractive index. The first strip and the second strip are embedded within the guiding portion extending along the first path such that a first optical mode received at the first end reaches the first strip before the second strip and such that the second strip extends to the second end. The first refractive index and the second refractive index are higher than a refractive index of the guiding portion, and a section of the first strip and a section of the second strip overlap to form an evanescent coupling region, such that converter is responsive to a first optical mode received at the first end to convert the first optical mode into a second optical mode with a smaller mode size along the first path towards the second end.