Tunable silicon nitride waveguide structure

Patent metadata

Field	Value
Publication number	US-12422624-B2
Application number	US-202318168617-A
Country	US
Kind code	B2
Filing date	Feb 14, 2023
Priority date	Feb 14, 2023
Publication date	Sep 23, 2025
Grant date	Sep 23, 2025

Abstract

Embodiments herein describe using an actuator to tune a waveguide. In one embodiment, the tunable waveguide includes a gap between the waveguide and cladding. The actuator can compress the cladding to shrink this air, bringing the cladding closer to the waveguide. Doing so changes the effective refractive index of the waveguide. Alternatively or additionally, the actuator can increase the gap.

First claim

We claim:

1. An optical device, comprising:
a cladding material;
a waveguide spaced apart from the cladding material by a gap; and
a capacitive actuator comprising a first conductive plate embedded in the cladding material and a second conductive plate embedded in the cladding material, the second conductive plate positioned relative to the first conductive plate such that the gap is positioned between the first conductive plate and the second conductive plate, the capacitive actuator configured to move the cladding material relative to the waveguide to vary the gap and change an effective refractive index of the waveguide.

2. The optical device of claim 1 , wherein the gap is disposed around at least three sides of the cladding material.

3. The optical device of claim 1 , wherein the cladding material is connected to supports at respective ends.

4. The optical device of claim 1 , wherein the capacitive actuator is configured to operate in a relaxed state where no force is applied by the capacitive actuator and the gap is at a maximum thickness, and an activated state where the capacitive actuator shrinks the gap to less than the maximum thickness.

5. The optical device of claim 4 , wherein the capacitive actuator is configured to move the cladding material closer to the waveguide when a voltage difference is applied to the first and second conductive plates.

6. The optical device of claim 5 , wherein the capacitive actuator operates in the relaxed state when no voltage is applied to the first and second conductive plates and in the activated state when the voltage difference is applied to the first and second conductive plates.

7. The optical device of claim 5 , wherein the waveguide is between the gap and the second conductive plate.

8. The optical device of claim 1 , wherein the waveguide comprises an athermal waveguide material.

9. The optical device of claim 1 , wherein the gap is less than 0.5 microns and the capacitive actuator is configured to shrink the gap by a range between 40 to 440 nm.

10. A method for adjusting a thickness of a gap defined between a cladding material and a waveguide, the method comprising:
adjusting, using a capacitive actuator comprising a first conductive plate embedded in the cladding material and a second conductive plate embedded in the cladding material and positioned relative to the first conductive plate such that the gap defined between the waveguide and the cladding material is positioned between the first conductive plate and the second conductive plate, the thickness of the gap proximate to the waveguide to move the cladding material closer to the waveguide.

11. The method of claim 10 , wherein the cladding material has a different refractive index than the gap, wherein moving the cladding material closer to the waveguide changes an effective refractive index of the waveguide.

12. The method of claim 10 , wherein the gap is disposed around at least three sides of the cladding material.

13. The method of claim 10 , wherein the cladding material is connected to supports at respective ends.

14. The method of claim 10 , wherein the adjusting comprises:
activating the capacitive actuator to decrease the thickness of the gap to less than a maximum thickness; and
deactivating the capacitive actuator to increase the thickness of the gap to the maximum thickness.

15. The method of claim 10 , wherein the adjusting comprises:
operating the capacitive actuator in a first activated state to decrease the thickness of the gap to a first thickness; and
operating the capacitive actuator in a second activated state to increase the thickness of the gap to a second thickness that is thicker than the first thickness and thinner than a maximum thickness of the gap.

16. A method comprising:
providing a capacitive actuator in a relaxed state in which a gap separating a waveguide from a cladding material has a maximum thickness, the capacitive actuator comprising a first conductive plate embedded in the cladding material and a second conductive plate embedded in the cladding material and positioned relative to the first conductive plate such that the gap is positioned between the first conductive plate and the second conductive plate; and
operating the capacitive actuator in an actuated state to move the cladding material closer to the waveguide to decrease a thickness of the gap.

17. The method of claim 16 , wherein the cladding material has a different refractive index than the gap, wherein moving the cladding material closer to the waveguide changes an effective refractive index of the waveguide.

18. The method of claim 16 , wherein the gap is disposed around at least three sides of the cladding material.

19. The method of claim 16 , wherein the cladding material is connected to supports at respective ends.

20. The method of claim 16 , wherein operating the capacitive actuator in the actuated state comprises applying a voltage to create a voltage difference between the first conductive plate and the second conductive plate.

Assignees

• Cisco Tech Inc

Inventors

• Traverso Matthew J
• Adams Donald J

Classifications

• G02F2203/055

  wavelength filtering · CPC title

• G02F1/2257

  the optical waveguides being made of semiconducting material · CPC title

• G02B6/3584

  constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching (MEMS per se B81B, B81C) · CPC title

• G02B6/3524

  the optical element being refractive · CPC title

• G02F1/0147

  based on thermo-optic effects (G02F1/132 takes precedence) · CPC title