Apparatus and method for coupling light

A semiconductor photonic device comprising:

• a first optical module;
• a second optical module;
• and
• an optical coupler for coupling light between the first optical module and the second optical module, wherein optical coupler comprises:
• a substrate;
• a first waveguide element provided in a first layer with respect to the substrate, wherein the first waveguide element comprises a first end and a second end, and wherein the first end of the first waveguide element is coupled to input light into a first end of the optical coupler or to output light from the first end of the optical coupler;
• and
• a second waveguide element provided in a second layer, the second layer arranged adjacent to the first layer, wherein the second waveguide element comprises a first end and a second end, and wherein the first end of the second waveguide element is coupled to input light into a second end of the optical coupler or to output light from the second end of the optical coupler;
• wherein the first waveguide element is configured to extend from the first end of the optical coupler towards the second end of the optical coupler, and wherein the second waveguide element is configured to extend from the second end of the optical coupler towards the first end of the optical coupler, such that the first waveguide element overlaps with the second waveguide element to adapt light passing between the first end of the first waveguide element and first end of the second waveguide element,
• wherein a length between the first end of the first waveguide element and the second end of the first waveguide element is shorter than a length between the first end of the optical coupler and the second end of the optical coupler, and
• wherein a length between the first end of the second waveguide element and the second end of the second waveguide element is shorter than a length between the first end of the optical coupler and the second end of the optical coupler.

A method of forming an optical coupler, the method comprising:

• providing a substrate;
• forming a first waveguide element in a first layer with respect to the substrate, wherein the first waveguide element comprises a first end and a second end, and wherein the first end of the first waveguide element is coupled to input light into a first end of the optical coupler or to output light from the first end of the optical coupler;
• and
• forming a second waveguide element in a second layer, the second layer formed adjacent to the first layer, wherein the second waveguide element comprises a first end and a second end, and wherein the first end of the second waveguide element is coupled to input light into a second end of the optical coupler or to output light from the second end of the optical coupler;
• wherein the first waveguide element is formed to extend from the first end of the optical coupler towards the second end of the optical coupler, and wherein the second waveguide element is formed to extend from the second end of the optical coupler towards the first end of the optical coupler, such that the first waveguide element overlaps with the second waveguide element to adapt light passing between the first end of the first waveguide element and first end of the second waveguide element,
• wherein a length between the first end of the first waveguide element and the second end of the first waveguide element is shorter than a length between the first end of the optical coupler and the second end of the optical coupler, and
• wherein a length between the first end of the second waveguide element and the second end of the second waveguide element is shorter than a length between the first end of the optical coupler and the second end of the optical coupler.