Forming optical components using selective area epitaxy
A mask material is deposited on a substrate or growth template. The substrate or growth template is compatible with crystalline growth of a crystalline optical material. Patterned portions of the mask material are removed to expose one or more regions of the substrate or growth template. The one or more regions have target shapes of one or more optical components. The crystalline optical material is selectively grown in the one or more regions to form the one or more optical components.
1. A method of forming a passive optical component of a photonic integrated circuit, comprising:
depositing a mask material on a substrate or growth template, the substrate or growth template compatible with crystalline growth of a crystalline optical material, the mask material deposited to a thickness that corresponds to a height of the passive optical component;
removing a patterned portion of the mask material to expose a region of the substrate or growth template, the region having a target shape of the passive optical component; and
selectively growing the crystalline optical material in the region to the height to form the passive optical component.
2. The method of claim 1 , further comprising temperature-annealing the mask material to reduce sidewall roughness of the mask material surrounding the region before selectively growing the crystalline optical material.
3. The method of claim 1 , further comprising, after selectively growing the crystalline optical material:
removing the mask material from the substrate or growth template, using a lift off with a liquid etchant; and
depositing or growing a cladding material over the crystalline optical material causing at least three sides of the passive optical component to be covered by the cladding material.
4. The method of claim 3 , wherein the cladding material comprises a crystalline cladding material that is grown over the passive optical component.
5. The method of claim 1 , wherein the passive optical component comprises a waveguide.
6. The method of claim 1 , wherein the passive optical component comprises a grating coupler.
7. The method of claim 1 , wherein the passive optical component comprises a ring resonator.
8. The method of claim 7 , wherein the ring resonator comprises two waveguides separated by a gap, and wherein first and second heights of the two waveguides are each at least five times greater than a width of the gap.
9. The method of claim 1 , wherein the passive optical component comprises a phase shifter.
10. The method of claim 1 , wherein the crystalline optical material comprises a III-V compound.
11. The method of claim 10 , wherein the III-V compound comprises a III-nitride compound.
12. The method of claim 1 , wherein selectively growing the crystalline optical material in the region increases an edge smoothness of the passive optical component, the edge smoothness affecting a quality factor of the passive optical component.
13. A method of forming an optical component, comprising:
depositing a mask material on a substrate or growth template, the substrate or growth template compatible with crystalline growth of a crystalline optical material, the mask material deposited to a thickness that does not exceed a height of the optical component;
removing a patterned portion of the mask material to expose a region of the substrate or growth template, the region having a target shape of the optical component;
etching into the substrate or growth template to form a trench corresponding to the target shape; and
selectively growing the crystalline optical material in the trench to form the optical component.
14. The method of claim 13 , further comprising lifting off the mask and forming a cladding layer over an exposed surface of the optical component.
15. The method of claim 14 , wherein the exposed surface is coplanar with the substrate or growth template.
16. The method of claim 14 , wherein the cladding layer is a crystalline material layer.
17. The method of claim 13 , wherein the etching into the substrate or growth template uses a different etch chemistry than the removing of the patterned portion of the mask.
18. The method of claim 13 , wherein the etching into the substrate or growth template uses a different etching tool than the removing of the patterned portion of the mask.
19. The method of claim 13 , wherein the optical component comprises two waveguides separated by a gap.
20. The method of claim 13 , wherein the optical component comprises an active optical component.