Multi-layer waveguide optical coupler

A method for using a photonic integrated circuit, comprising:

• emitting light from a light source towards a light receiving end of an optical coupler;
• wherein the optical coupler includes:
• a plurality of waveguide core layers formed from a waveguide core material having a first index of refraction, said waveguide core layers being (i) stacked vertically one over another, (ii) spaced apart vertically one from another, and (iii) extending from the light receiving end of the optical coupler longitudinally through the optical coupler to a light output end of the optical coupler, wherein at least one of the plurality of waveguide core layers includes a tapered region joined to a plurality of distinct waveguide paths, wherein each distinct waveguide path extends from the light receiving end of the optical coupler along a length of the optical coupler to the tapered region, and wherein the tapered region is proximate the light output end and narrows in a horizontal direction from a first width proximate the distinct waveguide paths to a second width at the light output end;
• and
• a cladding formed from a cladding material having a second index of refraction, said second index of refraction being less than the first index of refraction, said cladding material surrounding each of the plurality of waveguide core layers;
• wherein light propagating within outer ones of the plurality of waveguide core layers is directed toward an interior one of the plurality of waveguide core layers via evanescent coupling between adjacent ones of the plurality of waveguide core layers.

A method for using an optical coupler, comprising:

• receiving light from a light source at a light receiving end of an optical coupler;
• wherein the optical coupler includes:
• a plurality of waveguide core layers formed from a waveguide core material having a first index of refraction, said waveguide core layers being (i) stacked vertically one over another, (ii) spaced apart vertically one from another, and (iii) extending from the light receiving end of the optical coupler longitudinally through the optical coupler to a light output end of the optical coupler, wherein at least one of the plurality of waveguide core layers includes a tapered region joined to a plurality of distinct waveguide paths, wherein each distinct waveguide path extends from the light receiving end of the optical coupler along a length of the optical coupler to the tapered region, and wherein the tapered region is proximate the light output end and narrows in a horizontal direction from a first width proximate the distinct waveguide paths to a second width at the light output end;
• and
• a cladding formed from a cladding material having a second index of refraction, said second index of refraction being less than the first index of refraction, said cladding material surrounding each of the plurality of waveguide core layers;
• wherein light propagating within outer ones of the plurality of waveguide core layers is directed toward an interior one of the plurality of waveguide core layers via evanescent coupling between adjacent ones of the plurality of waveguide core layers;
• and
• transmitting light from an interior one of the plurality of waveguide core layers at a light output end of the optical coupler.