| 摘要 |
An apparatus comprises a first waveguide, a second waveguide and a transitional coupler. The first waveguide is defined by a first material and a second material. The first waveguide has a core and a cladding. The first material is the core of the first waveguide, and the second material is the cladding of the first waveguide. The second waveguide is defined by a third material and a fourth material. The second waveguide has a core and a cladding. The third material is the core of the second waveguide, and the fourth material is the cladding of the second waveguide. A cross-section of the core of the second waveguide is larger than a cross-section of the core of the first waveguide. The transitional coupler has a first end integrally formed with and operationally coupled to the first waveguide, and has a second end integrally formed with and operationally coupled to the second waveguide. The transitional coupler includes a co-directional grating.
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