Fabrication of waveguide structures

1. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel;

wherein:

the waveguiding layer comprises a first oxide layer and a second oxide layer, wherein the first oxide layer is to a first side of the second oxide layer and has a first index of refraction, and the second oxide layer has a second index of refraction lower than the first index of refraction;

the waveguiding layer further comprises a third oxide layer to a second side, opposite the first side, of the second oxide layer, wherein the third oxide layer has a third index of refraction lower than the first index of refraction, and

etching the fluid channel comprises etching into the third, second, and first oxide layers;

etching the first air gap comprises etching into the third, second, and first oxide layers; and

etching the second air gap comprises etching into the third, second, and first oxide layers.

2. The method of claim 1 , further comprising doping the waveguiding layer to create one or more doped regions in the waveguiding layer having a doped index of refraction lower than a surrounding index of refraction, wherein the one or more doped regions are adjacent to the solid-core waveguide.

3. The method of claim 2 , wherein the one or more doped regions are adjacent to the first air-gap and the second air-gap.

4. The method of claim 2 , wherein the one or more doped regions are adjacent to the fluid channel.

5. The method of claim 1 , further comprising doping the waveguiding layer to create one or more doped regions in the waveguiding layer having a doped index of refraction higher than a surrounding index of refraction, wherein the one or more doped regions form the solid-core waveguide.

6. The method of claim 1 , wherein the waveguide structure comprises a microfabricated fiber alignment feature.

7. The method of claim 1 , further comprising doping the waveguiding layer from a surface of the waveguiding layer upon which etching is performed to cause the waveguiding layer to have a gradient index of refraction that is highest near the doped surface.

8. The method of claim 7 , further comprising, after doping the waveguiding layer and before etching into the waveguiding layer, disposing a protective layer on the waveguiding layer, wherein affixing the cover layer to the waveguiding layer comprises affixing the cover layer to the protective layer.

9. The method of claim 1 , wherein:

etching the fluid channel comprises performing dry etching;

etching the first air gap comprises performing dry etching; and

etching the second air gap comprises performing dry etching.

10. The method of claim 1 , further comprising etching into the waveguiding layer behind an end of the solid-core waveguide, thereby forming an end of the solid-core waveguide.

11. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises an ARROW layer;

etching the fluid channel comprises etching into the waveguiding layer without etching into the ARROW layer;

etching the first air gap comprises etching into the waveguiding layer without etching into the ARROW layer; and

etching the second air gap comprises etching into the waveguiding layer without etching into the ARROW layer.

12. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises an ARROW layer;

the waveguide structure comprises an etch-stop layer between the ARROW layer and the waveguiding layer at a location corresponding to the fluid channel;

etching the fluid channel comprises:

etching into the waveguiding layer without etching into the ARROW layer;

dissolving the etch-stop layer;

etching the first air gap comprises etching into the waveguiding layer and the ARROW layer; and

etching the second air gap comprises etching into the waveguiding layer and the ARROW layer.

13. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises an ARROW layer;

etching the fluid channel comprises performing dry etching followed performing wet etching;

etching the first air gap comprises performing dry etching followed performing wet etching; and

etching the first air gap comprises performing dry etching followed performing wet etching.

14. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises an ARROW layer;

etching the fluid channel comprises etching partially into the waveguiding layer without etching through the waveguiding layer to the ARROW layer;

etching the first air gap comprises etching into the waveguiding layer and the ARROW layer; and

etching the second air gap comprises etching into the waveguiding layer and the ARROW layer.

15. The method of claim 14 , wherein:

etching the first air gap comprises etching into the waveguiding layer, the ARROW layer, and the substrate layer;

etching the second air gap comprises etching into the waveguiding layer, the ARROW layer, and the substrate layer.

16. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises an ARROW layer below the waveguiding layer;

the waveguide structure comprises an etch-stop layer between the ARROW layer and the waveguiding layer extending to a location corresponding the fluid channel, a location corresponding to the first air-gap, and a location corresponding to the second air-gap;

etching the fluid channel comprises etching into the waveguiding layer without etching into the ARROW layer;

etching the first air gap comprises etching into the waveguiding layer without etching into the ARROW layer;

etching the second air gap comprises etching into the waveguiding layer without etching into the ARROW layer; and

the method further comprises dissolving the etch-stop layer.

17. A method for fabricating a waveguide structure to form at least one solid-core waveguide from a waveguiding layer, the method comprising:

etching a fluid channel into the waveguiding layer;

etching a first air-gap and a second air gap into the waveguiding layer;

wherein etching the first and the second air-gaps creates a solid-core waveguide in the waveguiding layer between the first air-gap and the second air-gap; and

affixing a cover layer to the waveguiding layer to enclose the fluid channel,

wherein:

the waveguide structure comprises a substrate layer coupled to the waveguiding layer;

the method further comprises etching into the substrate to create a third air-gap adjacent to one or more of the fluidic channel and the solid-core waveguide, wherein the third air gap is configured to cause internal reflection of light propagating in one or more of the fluidic channel and the solid-core waveguide.

18. The method of claim 17 , further comprising disposing a lens element in the third air-gap, wherein the lens element is configured to collect light that escapes from the fluidic channel into the third air-gap.

19. The method of claim 17 , wherein etching into the substrate to create the third air-gap comprises undercutting one or more of the fluidic channel and the solid-core waveguide.