Birefringent waveplate and method for forming a waveplate having a birefringent metasurface

Patent metadata

Field	Value
Publication number	US-11747639-B2
Application number	US-201916518500-A
Country	US
Kind code	B2
Filing date	Jul 22, 2019
Priority date	Jul 22, 2019
Publication date	Sep 5, 2023
Grant date	Sep 5, 2023

Abstract

The present disclosure relates to a waveplate having a substrate forming an optic. The substrate may have an integral portion forming a plurality of angled columnar features on an exposed surface thereof. The plurality of angled columnar features may further be aligned parallel with a directional plane formed non-parallel to a reference plane, with the reference plane being normal to a surface of the substrate. The metasurface forms a birefringent metasurface.

First claim

What is claimed is:

1. A waveplate comprising:
a substrate forming an optic;
the substrate including an integral portion forming a plurality of angled columnar features on an exposed surface thereof, the plurality of angled columnar features forming a metasurface that extends partially into a thickness of the substrate;
each of the angled columnar features having a tapering wall that forms a non-uniform cross-sectional area over a length thereof;
the plurality of angled columnar features further being aligned parallel with a directional plane formed non-parallel to a reference plane, the reference plane being normal to a surface of the substrate, and such that the tapering wall of each said angled columnar feature is non-symmetrical along a first longitudinal axis of the substrate, and symmetrical along a second axis extending orthogonal to the first longitudinal axis; and
the metasurface forming a birefringent metasurface.

2. The waveplate of claim 1 , wherein the waveplate comprises a quarter waveplate.

3. The waveplate of claim 2 , wherein:
the metasurface forms a retardation layer;
a two axis index difference is defined by Δn; and
a thickness “L” of the retardation layer is defined by:
L =λ/(4Δ n ).

4. The waveplate of claim 1 , wherein the waveplate is comprised of fused silica glass.

5. The waveplate of claim 1 , wherein the plurality of angled columnar features each extend at an angle θ of between 60° and 75° relative to the reference plane.

6. The waveplate of claim 1 , wherein the plurality of angled columnar features each extend at an angle θ of between about 50° and 60° relative to the reference plane.

7. The waveplate of claim 1 , wherein the plurality of angled columnar features each extend at an angle θ of about 40° relative to the reference plane.

8. The waveplate of claim 1 , wherein the plurality of angled columnar features each have a length of at least 2λ, where λ is a wavelength of an optical signal passing through the waveplate.

9. The waveplate of claim 8 , wherein the plurality of angled columnar features each have a length of from 2λ to 4λ, where λ is a wavelength of an optical signal passing through the waveplate.

10. The waveplate of claim 1 , wherein the plurality of angled columnar features each have a length of about 1 μm.

11. The waveplate of claim 1 , wherein the plurality of angled columnar features each have a length of about 1.5λ, where λ is a wavelength of an optical signal passing through the waveplate.

12. The waveplate of claim 1 , wherein the plurality of angled columnar features comprise a plurality of angled columnar projections forming an integral portion of the substrate.

13. The waveplate of claim 1 , wherein the plurality of angled columnar features comprise a plurality of angled columnar recesses forming an integral portion of the substrate.

14. A waveplate for receiving an optical signal, the waveplate comprising:
a substrate forming an optic;
the substrate including an integral portion forming a metasurface formed on an exposed surface thereof, and extending partially into a thickness of the substrate, the metasurface including a plurality of angled columnar features formed using a portion of the substrate, the angled columnar features being in a generally uniform grid-like pattern and each having a length of between 1.5λ and 4λ, where λ is a wavelength of the optical signal passing through the waveplate;
each of the angled columnar features having a tapering wall that forms a non-uniform cross-sectional area over a length thereof;
the plurality of angled columnar features further being aligned parallel with a directional plane defined by an angle θ, where θ is between 40° and 75° relative to a reference plane, the reference plane being normal to a surface of the substrate;
the tapering wall of each said angled columnar feature further being non-symmetrical along a first longitudinal axis of the substrate, and symmetrical along a second axis extending orthogonal to the first longitudinal axis; and
the metasurface forming a birefringent metasurface.

15. The waveplate of claim 14 , wherein the angled columnar features comprise at least one of angled columnar projections or angled columnar recesses, which form an integral portion of the substrate.

16. A method for forming a birefringent waveplate, the method comprising:
providing a substrate;
creating a mask on an outer surface of the substrate; and
using a material removal process, together with the mask, to remove select material portions from the substrate to form a plurality of angled columnar features which collectively extend partially into a thickness of the substrate, and collectively form a birefringent metasurface using a portion of the substrate, each of the angled columnar features further having a tapering wall that forms a non-uniform cross-sectional area over a length thereof, and further using the material removal process to form each said angled columnar feature such that each said tapering wall is non-symmetrical along a first longitudinal axis of the substrate, and symmetrical along a second axis extending orthogonal to the first longitudinal axis; and
the birefringent metasurface forming an integral portion of the substrate.

17. The method of claim 16 , wherein removing select material portions from the substrate to form the angled columnar features comprises removing select material portions to form a plurality of angled columnar projections which are integral with the substrate.

18. The method of claim 16 , wherein removing select material portions from the substrate to form the angled columnar features comprises removing select material portions to form a plurality of columnar angled recesses within a portion of the substrate.

19. The method of claim 16 , wherein removing the select material portions further comprises creating each said one of the plurality of angled columnar features with a length of between 1.5λ and 4λ, where λ is a wavelength of an optical signal passing through the waveplate.

20. The method of claim 16 , wherein using a material removal process comprises using one of a reactive ion etching (RIE) process or a reactive ion beam etching (RIBE) process.

21. The method of claim 16 , wherein creating a mask comprises depositing nano-particles on the outer surface of the substrate to impart to the mask a wavelength shorter than a wavelength λ of an optical signal passing through the waveplate.

22. The method of claim 16 , wherein creating a mask comprises forming a mask layer of material on the outer surface of the substrate and creating nano-voids in the mask layer of material.

Assignees

• L Livermore Nat Security Llc

Inventors

• Feigenbaum Eyal
• Bude Jeffrey D
• Di Nicola Jean-Michel
• Nguyen Hoang T
• Stolz Christopher J

Classifications

• G02B27/283 Primary

  used for beam splitting or combining · CPC title

• G02B5/3083

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• G02B6/272

  comprising polarisation means for beam splitting and combining · CPC title

• G02B1/002 Primary

  made of materials engineered to provide properties not available in nature, e.g. metamaterials · CPC title

• G02B5/3091

  for use in the UV · CPC title