Broadband flat optical elements and methods of manufacture

Patent metadata

Field	Value
Publication number	US-10365535-B2
Application number	US-201715846065-A
Country	US
Kind code	B2
Filing date	Dec 18, 2017
Priority date	Dec 18, 2017
Publication date	Jul 30, 2019
Grant date	Jul 30, 2019

Abstract

Flat optical elements including a multi-level metasurface stack having two or more metasurface levels. Each metasurface level includes an arrangement of nanostructures, or protrusions, of one or more optically transmissive materials. A metasurface level may further include another optically transmissive material between the nanostructures, achieving a desired index contrast. Another metasurface level including additional nanostructures may be over a planar surface of this additional transmissive material. Another optically transmissive material may be between the additional nanostructures. This architecture may be followed for any number of levels, (e.g., a bi-layer, tri-layer, etc.). Each metasurface within the multi-level metasurface structure may be tuned to a particular optical wavelength. Such a multi-level metasurface may have greater bandwidth and/or achieve higher optical efficiency for a given band than a single metasurface. Molding techniques may be employed in metasurface fabrication to reduce the starting material cost and fabrication cost.

First claim

What is claimed is:

1. An optical element, comprising:
a plurality of first nanostructures spatially distributed over an area of a substrate, wherein the substrate and the first nanostructures are transmissive over a visible light band, and wherein the first nanostructures have dimensions that induce a phase shift of a first non-zero magnitude for a first wavelength within the band;
a dielectric material over and between the first nanostructures, wherein the dielectric material is transmissive over the band;
a plurality of second nanostructures over the first nanostructures with the dielectric material therebetween, wherein the second nanostructures are transmissive over the band and have dimensions that induce a phase shift of at least the first magnitude for a second wavelength within the band, and wherein the first and second wavelengths differ by at least 50 nm.

2. The optical element of claim 1 , wherein the dielectric material is a first dielectric material, and the element further comprises:
a second dielectric material over the second nanostructures; and
a plurality of third nanostructures over the second nanostructures with the second dielectric material therebetween, wherein the third nanostructures are transmissive over the band and have dimensions that induce a phase shift of at least the first magnitude for a third wavelength of the band, wherein:
the first wavelength is a center wavelength of a first of a red, green and blue wavelength band;
the second wavelength is a center wavelength of a second of the red, green and blue wavelength band; and
the third wavelength is a center wavelength of a third of the red, green and blue wavelength band.

3. The optical element of claim 2 , further comprising a third dielectric material over the third nanostructures.

4. The optical element of claim 2 , wherein:
the first dielectric material has a first index contrast with the first nanostructures at the first wavelength, and a second index contrast with the first nanostructures at the second wavelength;
the second dielectric material has a third index contrast with the second nanostructures at the second wavelength; and
a difference between the first and second contrasts is greater than a difference between the first and third contrasts.

5. The optical element of claim 1 , wherein:
the first nanostructures have a lateral dimension parallel to a plane of the substrate, and the lateral dimension of the first nanostructures spans a first range from a first minimum lateral dimension to a first maximum lateral dimension;
the second nanostructures have a lateral dimension parallel to the plane of the substrate, and the lateral dimension of the second nanostructures spans a second range from a second minimum lateral dimension to a second maximum lateral dimension, wherein at least the first minimum lateral dimension is different than the second minimum lateral dimension.

6. The optical element of claim 5 , wherein:
the first minimum lateral dimension is less than the second minimum lateral dimension and the first maximum lateral dimension is no greater than the second minimum lateral dimension; or
the second minimum lateral dimension is less than the first minimum lateral dimension and the second maximum lateral dimension is no greater than the first minimum lateral dimension.

7. The optical element of claim 5 , wherein:
the first nanostructures have a first height, orthogonal to the plane of the substrate; and
the second nanostructures have a second height, orthogonal to the plane of the substrate, different than the first height.

8. The optical element of claim 7 , wherein:
the first wavelength is longer than the second wavelength, the first height is greater than the second height, and the first minimum lateral dimension is greater than the second minimum lateral dimension; or
the second wavelength is longer than the first wavelength, the second height is greater than the first height, and the second minimum lateral dimension is greater than the first minimum lateral dimension.

9. The optical element of claim 8 , wherein:
the first wavelength is at least 600 nm, the first height is at least 420 nm, and the first minimum lateral dimension is no less than 90 nm; and
the second wavelength is at least 500 nm, the second height is at least 350 nm, and the second maximum lateral dimension is no more than 90 nm.

10. The optical element of claim 1 , wherein:
the optical element is a converging lens, and
the first nanostructures have a spatial distribution over the substrate area that focuses the first wavelength, to a focal point at a first focal length; and
the second nanostructures have a spatial distribution over the substrate area that focuses the second wavelength, to the focal point at the first focal length.

11. The optical element of claim 1 , wherein the first nanostructures, the second nanostructures, or both the first and second nanostructures further comprise at least one of: a compound comprising at least titanium and oxygen, a compound comprising at least silicon and nitrogen, a compound comprising at least hafnium and oxygen, a compound comprising at least gallium and phosphorus, crystalline diamond, or diamond-like carbon.

12. The optical element of claim 1 , wherein the first nanostructures, the second nanostructures, or both the first and second nanostructures comprise a core of a first composition and a cladding, of a second composition, over at least a sidewall of the core.

13. The optical element of claim 12 , wherein the cladding has a thickness less than 50 nm and comprises at least one of titanium oxide, crystalline or amorphous gallium phosphide, crystalline diamond, or diamond-like carbon.

14. A display device, comprising:
a light source operable to emit visible light;
an optical element to couple the light to a viewport, wherein the optical element comprises:
a plurality of first nanostructures spatially distributed over an area of a substrate that is within an optical path of the light, wherein the substrate and the first nanostructures are transmissive of light, and wherein the first nanostructures have dimensions that induce a phase shift of a first non-zero magnitude for a center wavelength of a first of a red, blue or green wavelength band;
a first dielectric material over the first nanostructures, wherein first dielectric material is transmissive of the light;
a plurality of second nanostructures over the first nanostructures with the dielectric material therebetween, wherein the second nanostructures are transmissive of the light and have dimensions that induce a phase shift of at least the first magnitude for a center wavelength of a second of the red, blue or green wavelength band;
a second dielectric material over the second nanostructures, wherein second dielectric material is transmissive of the light;
a plurality of third nanostructures over the second nanostructures with the second dielectric material therebetween, wherein the third nanostructures are transmissive of the light and have dimensions that induce a phase shift of at least the first magnitude for a center wavelength of a third of the red, blue or green wavelength band; and
one or more processors to receive image data and control the light source based on the image data.

15. The display device of claim 14 , further comprising:
a battery;
a memory; and
a wireless communications system coupled to at least one of the memory and the processor to receive the image data from a source remote from the display device.

16. A method of fabricating an optical element, th

Assignees

• Intel Corp

Inventors

• Ahmed Khaled
• Hicks Richmond

Classifications

• B29D11/0074

  Production of other optical elements not provided for in B29D11/00009- B29D11/0073 · CPC title

• G02B6/003

  Lens or lenticular sheet or layer · CPC title

• C23C16/45525

  Atomic layer deposition [ALD] · CPC title

• G09G3/32

  semiconductive, e.g. using light-emitting diodes [LED] · CPC title

• G09G2320/0626

  for control of overall brightness · CPC title