Fabrication of optical metasurfaces

1. A method for fabricating an optical metasurface, the method comprising:

depositing a conductive layer over a holographic region of a wafer;

depositing a dielectric layer over the conducting layer;

patterning a hard mask on the dielectric layer; and

etching the dielectric layer to form a plurality of dielectric pillars with a plurality of nano-scale gaps between the pillars.

2. The method of claim 1 , wherein the patterning is performed by e-beam lithography.

3. The method of claim 1 , wherein the patterning is performed by deep UV immersion lithography.

4. The method of claim 1 , further comprising filling the plurality of nano-scale gaps with a refractive index tunable core material.

5. The method of claim 4 , wherein the refractive index tunable core material comprises a liquid crystal or EO polymers.

6. The method of claim 5 , the step of filling the plurality of nano-scale gaps comprising:

preparing the surface to be hydrophobic or hydrophilic;

spin coating the liquid crystal over the plurality of pillars;

filling the liquid crystal into the nano-scale gap by a capillary action; and

encapsulating the liquid crystal with a clear coating.

7. The method of claim 5 , the step of filling the plurality of nano-scale gaps comprising:

applying a coating to a first portion of the plurality of nano-scale gaps;

spin coating the liquid crystal onto the plurality of dielectric pillars;

filling the liquid crystal into a second portion of the plurality of nano-scale gaps by a capillary action; and

encapsulating the liquid crystal with a clear coating.

8. The method of claim 1 , wherein the plurality of dielectric pillars comprises a constant gap between each of the pillars.

9. The method of claim 1 , wherein the plurality of dielectric pillars comprises a plurality of pairs of dielectric pillars.

10. The method of claim 9 , wherein the gap between each pair of pillars is smaller than the gap between two adjacent pairs of pillars.

11. The method of claim 1 , wherein the plurality of dielectric pillars comprises amorphous silicon.

12. The method of claim 1 , wherein the refractive index tunable core material comprises chalcogenide glass.

13. The method of claim 12 , the step of filling the plurality of nano-scale gaps comprising:

depositing the chalcogenide glass over the dielectric pillars by sputtering; and removing the chalcogenide glass from all areas except inside the plurality of nano-scale gaps.

14. The method of claim 1 , the step of depositing a dielectric layer over a conducting layer comprising:

depositing an etch-stop dielectric layer over the conducting layer; and

depositing the dielectric layer over the etch-stop dielectric layer.

15. The method of claim 14 , wherein the etch-stop dielectric layer comprises Al 2 O 3 .

16. The method of claim 1 , wherein the aspect ratio of height to width of the nano-scale gap is at least 5.

17. The method of claim 1 , the step of patterning a hard mask on the dielectric layer comprising:

depositing a hard mask over the dielectric layer;

patterning the hard mask to remove a first portion of the hard mask near an interconnect region;

patterning the hard mask by a high resolution process to form the nano-scale gap;

plasma etching the hard mask to remove a second portion of the hard mask in the nano-scale gap to expose the dielectric layer.

18. The method of claim 17 , wherein the hard mask comprises Al 2 O 3 .

19. The method of claim 17 , wherein patterning the hard mask to remove a first portion of the hard mask near an interconnect region is performed by a low resolution process.

20. The method of claim 1 , further comprising forming a plurality of conductive contacts over an interconnect region of the wafer for wire bonding to a CMOS, the plurality of conductive contacts configured to apply voltage to the plurality of dielectric pillars.

21. An optical metasurface fabricated by the method of claim 1 .