Controlling evanescent waves on dielectric waveguides

1. A device comprising:

a first waveguide portion disposed on a substrate;

a second waveguide portion; and

a third waveguide portion disposed between the first waveguide portion and the second waveguide portion, wherein the third waveguide portion is configured to carry a signal based on a refractive index of the third waveguide portion matching an effective refractive index of an optical mode of a combination of the first waveguide portion and the second waveguide portion.

2. The device of claim 1 , wherein the third waveguide portion has a lower refractive index than a refractive index of the combination of the first waveguide portion and the second waveguide portion.

3. The device of claim 1 , wherein the second waveguide portion and the third waveguide portion are formed on the substrate.

4. The device of claim 1 , wherein the third waveguide portion is disposed above the first waveguide portion, and the second waveguide portion is disposed above the third waveguide portion.

5. The device of claim 1 , further comprising a modulation element configured to modify one or more of the refractive index or the effective refractive index to modulate the signal, wherein the modulation element comprises one or more of a heater or a voltage element.

6. The device of claim 1 , wherein the third waveguide portion separates the first waveguide portion and the second waveguide portion by a distance in a range of one or more of about 200 nm to about 1 μm, about 200 nm to about 10 μm, about 250 nm to about 1 μm, about 250 nm to about 10 μm, about 300 nm to about 1 μm, about 300 nm to about 10 μm, about 1 nm to about 10 μm, or about 1 nm to about 100 μm.

7. The device of claim 1 , wherein the first waveguide portion and the second waveguide portion comprise one or more of a first dielectric material, silicon, or silicon nitride, and wherein the third waveguide portion comprises one or more of a second dielectric material, silicon oxynitride, or alumina.

8. The device of claim 1 , wherein the refractive index matching the effective refractive index comprises the refractive index matching, within a threshold range, the effective refractive index.

9. The device of claim 1 , wherein the first waveguide portion and the second waveguide portion are solid and the third waveguide portion is a liquid.

10. The device of claim 1 , wherein the effective refractive index of the optical mode is based on one or more of: a geometry of the combination of the first waveguide portion and the second waveguide portion, a wavelength associated with the optical mode, or a material of the combination of the first waveguide portion and the second waveguide portion.

11. The device of claim 1 , wherein the optical mode of the combination of the first waveguide portion and the second waveguide portion comprises an optical mode of a resulting waveguide if the distance between the second waveguide portion and the first waveguide portion was reduced to zero.

12. A method comprising:

forming a first waveguide portion on a substrate;

forming a second waveguide portion; and

forming a third waveguide portion between the first waveguide portion and the second waveguide portion, wherein the third waveguide portion is configured to carry a signal based on a refractive index of the third waveguide portion matching an effective refractive index of an optical mode of a combination of the first waveguide portion and the second waveguide portion.

13. The method of claim 12 , further comprising determining a material for forming the third waveguide portion based on the material having the refractive index matching the effective refractive index.

14. The method of claim 12 , wherein the third waveguide portion has a lower refractive index than a refractive index of the combination of the first waveguide portion and the second waveguide portion.

15. The method of claim 12 , wherein the second waveguide portion and the third waveguide portion are formed on the substrate.

16. The method of claim 12 , further comprising modifying the signal by modifying, using one or more of heat or voltage, one or more of the refractive index or the effective refractive index.

17. The method of claim 12 , wherein the third waveguide portion separates the first waveguide portion and the second waveguide portion by a distance in a range of one or more of about 200 nm to about 1 μm, about 200 nm to about 10 μm, about 250 nm to about 1 μm, about 250 nm to about 10 μm, about 300 nm to about 1 μm, about 300 nm to about 10 μm, about 1 nm to about 10 μm, or about 1 nm to about 100 μm.

18. The method of claim 12 , wherein the first waveguide portion and the second waveguide portion comprise one or more of a first dielectric material, silicon, or silicon nitride, and wherein the third waveguide portion comprises one or more of a second dielectric material, silicon oxynitride, or alumina.

19. The method of claim 12 , wherein the refractive index matching the effective refractive index comprises the refractive index matching, within a threshold range, the effective refractive index.

20. The method of claim 12 , wherein the first waveguide portion and the second waveguide portion are solid and the third waveguide portion is a liquid.

21. The method of claim 12 , wherein the effective refractive index of the optical mode is based on one or more of: geometry of the combination of first waveguide portion and the second waveguide portion, a wavelength associated with the optical mode, or a material of the combination of the first waveguide portion and the second waveguide portion.