Tunable grating couplers containing a material with a variable refractive index
Structures including a grating coupler and methods of forming a structure that includes a grating coupler. The grating coupler includes segments that are positioned with a spaced relationship on a slab layer. The segments contain an active material configured to have a first state with a first refractive index and a second state with a second refractive index in response to an applied stimulus. The first and second states may be produced by applying different sets of bias voltages to the segments as the applied stimulus.
1. A structure comprising:
a slab layer;
a grating coupler including a plurality of segments positioned with a spaced relationship on the slab layer, the plurality of segments comprised of an active material configured to have a first state with a first refractive index and a second state with a second refractive index in response to an applied stimulus;
a first dielectric layer over the slab layer and the plurality of segments, the first dielectric layer comprising a dielectric material; and
a plurality of first contacts in the first dielectric layer, each of the plurality of first contacts coupled to one of the plurality of segments,
wherein the plurality of segments are embedded in the first dielectric layer such that spaces between the plurality of segments are filled by the dielectric material of the first dielectric layer.
2. The structure of claim 1 further comprising:
a second contact in the first dielectric layer, the second contact coupled to the slab layer.
3. The structure of claim 1 wherein the active material is a conducting oxide.
4. The structure of claim 1 wherein the active material is a phase change material.
5. The structure of claim 1 wherein the active material is a two-dimensional material or a polymer.
6. The structure of claim 1 further comprising:
a waveguide core coupled to the grating coupler,
wherein the slab layer is integral with the waveguide core.
7. The structure of claim 1 wherein the slab layer has a tapered shape, and the plurality of segments have different lengths.
8. The structure of claim 1 further comprising:
a waveguide core coupled to the grating coupler,
wherein the slab layer is distinct from the waveguide core.
9. The structure of claim 8 wherein the waveguide core is comprised of a dielectric material, and the slab layer is comprised of a conductor.
10. The structure of claim 1 wherein the plurality of segments are arranged in a plurality of rows, and each of the plurality of rows contains more than one of the plurality of segments.
11. The structure of claim 10 wherein the slab layer has a tapered shape, and the plurality of rows contain different numbers of the plurality of segments.
12. The structure of claim 1 further comprising:
a second dielectric layer positioned on the slab layer between the plurality of segments and the slab layer.
13. The structure of claim 1 further comprising:
a conductor layer positioned on the slab layer between the plurality of segments and the slab layer.
14. The structure of claim 1 further comprising:
a heater positioned proximate to the plurality of segments.
15. A method comprising:
forming a slab layer; and
forming a grating coupler including a plurality of segments positioned with a spaced relationship on the slab layer;
forming a first dielectric layer over the slab layer and the plurality of segments; and
forming a plurality of first contacts in the first dielectric layer,
wherein the first dielectric layer comprises a dielectric material, each of the plurality of first contacts is coupled to one of the plurality of segments, the plurality of segments are embedded in the first dielectric layer such that spaces between the plurality of segments are filled by the dielectric material of the first dielectric layer, the plurality of segments are comprised of an active material configured to have a first state with a first refractive index and a second state with a second refractive index in response to an applied stimulus.
16. The method of claim 15 wherein forming the grating coupler including the plurality of segments positioned with the spaced relationship on the slab layer comprises:
depositing a layer of the active material; and
patterning the layer with lithography and etching processes.
17. The method of claim 15 wherein the active material is a conducting oxide.
18. The method of claim 15 further comprising:
forming a second dielectric layer on the slab layer,
wherein the second dielectric layer is positioned between the plurality of segments and the slab layer.
19. The method of claim 15 further comprising:
forming a conductor layer on the slab layer
wherein the conductor layer is positioned between the plurality of segments and the slab layer.
20. The method of claim 15 further comprising:
forming a second contact in the first dielectric layer,
wherein the second contact is coupled to the slab layer.