Variable height slanted grating method
An apparatus with a grating structure and a method for forming the same are disclosed. The grating structure includes forming a recess in a grating layer. A plurality of channels is formed in the grating layer to define slanted grating structures therein. The recess and the slanted grating structures are formed using a selective etch process.
1. A structure for use in a waveguide, comprising:
a substrate having a grating layer thereon, wherein a recessed structure is formed in the grating layer, the recessed structure comprising:
a first end;
a second end; and
a depth, wherein the depth changes from the first end to the second end; and
a plurality of channels formed in the grating layer below the recessed structure, each channel partially defining a portion of a plurality of grating structures, wherein:
bottom ends of the plurality of channels are coplanar;
top surfaces of the plurality of grating structures are coplanar and partially define the changing depth of the recessed structure; and
a depth of the plurality of grating structures changes from the first end to the second end defined by the recessed structure.
2. The structure of claim 1 , wherein the depth of the plurality of grating structures changes linearly from the first end to the second end.
3. The structure of claim 1 , wherein each grating structure has a depth between about 5 nm and about 700 nm.
4. The structure of claim 1 , wherein each grating structure is slanted at an angle between about 0 degrees and about 70 degrees.
5. The structure of claim 1 , wherein the grating layer is formed from an optically transparent material having a refractive index of about 1.3 or higher.
6. A structure for use in a waveguide, comprising:
a substrate having a grating layer thereon;
a recess formed in the grating layer, wherein the recess has a depth that changes a first direction, a second direction, and a third direction to define a three dimensional shape; and
a plurality of channels formed in the grating layer below the recess, each channel partially defining a portion of a plurality of grating structures, wherein bottom ends of the plurality of channels are coplanar, and wherein a depth of the plurality of grating structures changes in the first direction, the second direction, and the third direction as defined by the recess.
7. The structure of claim 6 , wherein the recess has a saddle-point shape.
8. The structure of claim 6 , wherein the recess has a positive curvature.
9. The structure of claim 6 , wherein the recess has a negative curvature.
10. The structure of claim 6 , wherein the grating layer is formed from an optically transparent material having a refractive index of about 1.3 or higher.
11. The structure of claim 6 , wherein each grating structure has a depth between about 5 nm and about 700 nm.
12. The structure of claim 6 , wherein each grating structure is slanted at an angle between about 0 degrees and about 70 degrees.
13. A structure for use in a waveguide, comprising:
a substrate having a grating layer thereon, wherein a recessed structure is formed in the grating layer, the recessed structure comprising:
a first end;
a second end; and
a depth, wherein the depth of the recessed structure changes from the first end to the second end; and
a plurality of channels formed in the grating layer below the recessed structure, each channel partially defining a portion of a plurality of grating structures, wherein bottom ends of the plurality of channels are coplanar, and wherein a depth of the plurality of grating structures changes non-linearly from the first end to the second end as defined by the recessed structure.
14. The structure of claim 13 , wherein the depth of the plurality of grating structures oscillates from the first end to the second end.
15. The structure of claim 13 , wherein the depth of the recess changes in the first direction and the second direction to define a curved shape.
16. The structure of claim 13 , wherein each grating structure has a depth between about 5 nm and about 700 nm.
17. The structure of claim 13 , wherein each grating structure is slanted at an angle between about 0 degrees and about 70 degrees.
18. The structure of claim 13 , wherein the grating layer is formed from an optically transparent material having a refractive index of about 1.3 or higher.