Forming optical components using selective area epitaxy

1. A method 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;

removing patterned portions of the mask material to expose two or more regions of the substrate or growth template, the two or more regions having target shapes of two or more optical components and a gap between the two or more regions; and

selectively growing the crystalline optical material in the two or more regions to form the two or more optical components, the gap facilitating evanescent coupling between the two or more optical components.

2. The method of claim 1 , further comprising temperature-annealing the mask material to reduce sidewall roughness of the mask material surrounding the two or more regions 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.

4. The method of claim 1 , wherein the two or more optical components do not extend above the mask material, the method further comprising depositing an amorphous cladding material over the two or more optical components.

5. A method 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, wherein the mask material comprises a first cladding material;

removing patterned portions of the mask material to expose one or more regions of the substrate or growth template, the one or more regions having target shapes of one or more optical components;

selectively growing the crystalline optical material in the one or more regions to form the one or more optical components; and

depositing a second amorphous cladding material over the selectively grown crystalline optical material causing at least three sides of the optical components to be covered by the first cladding material and the second amorphous cladding material.

6. The method of claim 1 , wherein the crystalline optical material comprises a III-V compound.

7. The method of claim 6 , wherein the III-V compound comprises a III-nitride compound.

8. The method of claim 5 , wherein the one or more optical components are part of a passive optical device, the passive optical device comprising two guide layers with first and second dispersion responses that combine to create an anomalous dispersion about a target wavelength.

9. The method of claim 1 , wherein the substrate or template comprises an AlN substrate or an AlN template on an Al 2 O 3 or Si substrate.

10. The method of claim 1 , wherein the mask material comprises at least one of SiO 2 , SiN, and TiN.

11. The method of claim 1 , wherein the two or more optical components comprise curved waveguides defined by the patterned portions of the mask material.

12. The method of claim 1 , wherein the two or more optical components are part of a passive optical device, the passive optical device including at least one of a waveguide, a ring resonator, and a phase shifter.

13. The method of claim 1 , wherein the two or more optical components have a height that is smaller than that of the mask.

14. The method of claim 1 , wherein the pattern is used to form an aspect ratio in each of the two or more optical components that is greater than 5, wherein the aspect ratio is a ratio between a thickness of one of the optical components and an adjacent one of the optical components.

15. The method of claim 1 , wherein the mask has a thickness that is greater than 200 nm.

16. The method of claim 1 , wherein removing the patterned portions of the mask material further comprises etching one or more trenches in the substrate or growth template in the one or more regions, wherein the crystalline optical material is selectively grown in the trenches to form the two or more optical components.