Non-linear optical crystal with anti-reflective nanostructured surface

Patent metadata

Field	Value
Publication number	US-12360432-B2
Application number	US-202117344881-A
Country	US
Kind code	B2
Filing date	Jun 10, 2021
Priority date	Jun 10, 2020
Publication date	Jul 15, 2025
Grant date	Jul 15, 2025

Abstract

A non-linear optical crystal, such as a Lithium triborate (LiB 3 O 5 or LBO) crystal, includes a first nanostructured optical surface including distributed pillars and gaps having random heights and cross sections to provide anti-reflection control and scatter control of first light incident on the first structured optical surface. The LBO crystal has an anti-reflective random structured optical surface formed by selective substitution of the surface species Boron-pentoxide (B 3 O 5 − ) by Lithium Fluoride (LiF), resulting in a depletion layer with low reflectivity and low reflective scatter in the visible, ultraviolet (UV), and near infrared (IR) bands. The LBO crystal with the anti-reflective structured optical surface may be a monolithic structure and thus need not include a coating of an anti-reflective (AR) material, although the LBO crystal may include an optical surface coated by an AR material. The pillars and gaps may be randomly distributed or periodically distributed on the optical surface.

First claim

What is claimed is:

1. A non-linear optical crystal, comprising:
a first structured optical surface including distributed pillars and gaps having heights and cross sections to provide anti-reflection control and scatter control of first light incident on the first structured optical surface; and
a second optical surface,
wherein the non-linear optical crystal is a Lithium triborate (LBO) crystal, and wherein the first structured optical surface is depleted of Boron (B).

2. The non-linear optical crystal of claim 1 , wherein the second optical surface comprises a second structured optical surface including distributed pillars and gaps having heights and cross sections to provide anti-reflection control and scatter control of second light incident on the second structured optical surface.

3. The non-linear optical crystal of claim 2 , wherein the pillars and gaps are randomly distributed on the first structured optical surface and the second structured optical surface, and wherein pillars and gaps have random heights and random cross sections.

4. The non-linear optical crystal of claim 2 , wherein the pillars and gaps distributed on the first structured optical surface and the second structured optical surface have periodically varying heights and cross section values across the first optical surface and the second optical surface.

5. The non-linear optical crystal of claim 1 , wherein the second optical surface includes an anti-reflective coating on the second optical surface.

6. The non-linear optical crystal of claim 1 , wherein the non-linear optical crystal has an optical axis and wherein the first structured optical surface is a planar surface orthogonal to the optical axis.

7. The non-linear optical crystal of claim 1 , wherein the first structured optical surface comprises a curved surface.

8. The non-linear optical crystal of claim 1 , wherein the non-linear crystal has an optical axis and wherein the first structured optical surface is a wedged planar surface at an acute angle relative to the optical axis.

9. The non-linear optical crystal of claim 1 , wherein the heights of the pillars extend along longitudinal axes of the pillars and the longitudinal axes are parallel to a direction of the first light incident on the first structured optical surface.

10. The non-linear optical crystal of claim 1 , wherein the first light has a first wavelength in the infrared spectrum and a second light generated in the non-linear optical crystal in response to the first light has a second wavelength in the visible spectrum.

11. The non-linear optical crystal of claim 1 , wherein the pillars and gaps are configured to have average heights and average cross-sections that are a function of a shortest wavelength and a longest wavelength of light to be propagated in the non-linear crystal.

12. The non-linear optical crystal of claim 11 , wherein the gaps have an average value equal to 70% of the value of the shortest wavelength and the pillars have an average height equal to one half the longest wavelength.

13. The non-linear optical crystal of claim 1 further comprising a conformal moisture barrier layer covering the pillars and gaps of the first structured optical surface.

14. The non-linear optical crystal of claim 1 , wherein the first structured optical surface is enriched with Lithium Fluoride (LiF).

15. An LBO crystal, comprising:
a first structured optical surface including a plurality of randomly distributed nanostructures including pillars having heights and gaps having cross sections, the gaps positioned between the pillars and the cross sections of the gaps configured to provide a gradient index profile to provide anti-reflection control and the heights of pillars configured to provide scatter control for light incident upon first structured optical surface, wherein the first structured optical surface is depleted of Boron (B).

16. The LBO crystal of claim 15 , wherein the first structured optical surface is enriched with Lithium Fluoride (LiF).

17. A non-linear optical crystal, comprising:
a first structured optical surface including distributed pillars and gaps having heights and cross sections to provide anti-reflection control and scatter control of first light incident on the first structured optical surface;
a second optical surface; and
a conformal moisture barrier layer covering the pillars and gaps of the first structured optical surface.

18. The non-linear optical crystal of claim 17 , wherein the second optical surface comprises a second structured optical surface including distributed pillars and gaps.

19. The non-linear optical crystal of claim 18 , wherein the pillars and gaps are randomly distributed on the first structured optical surface and the second structured optical surface, and wherein pillars and gaps have random heights and random cross sections.

20. The non-linear optical crystal of claim 18 , wherein the pillars and gaps distributed on the first structured optical surface and the second structured optical surface have periodically varying heights and cross section values across the first optical surface and the second optical surface.

21. The non-linear optical crystal of claim 17 , wherein the second optical surface includes an anti-reflective coating on the second optical surface.

22. The non-linear optical crystal of claim 17 , wherein the non-linear optical crystal has an optical axis and wherein the first structured optical surface is a planar surface orthogonal to the optical axis.

23. The non-linear optical crystal of claim 17 , wherein the first structured optical surface comprises a curved surface.

24. The non-linear optical crystal of claim 17 , wherein the non-linear crystal has an optical axis and wherein the first structured optical surface is a wedged planar surface at an acute angle relative to the optical axis.

25. The non-linear optical crystal of claim 17 , wherein the heights of the pillars extend along longitudinal axes of the pillars and the longitudinal axes are parallel to a direction of the first light incident on the first structured optical surface.

26. The non-linear optical crystal of claim 17 , wherein the first light has a first wavelength in the infrared spectrum and a second light generated in the non-linear optical crystal in response to the first light has a second wavelength in the visible spectrum.

27. The non-linear optical crystal of claim 17 , wherein the pillars and gaps have average heights and average cross-sections that are a function of a shortest wavelength and a longest wavelength of light to be propagated in the non-linear crystal.

28. The non-linear optical crystal of claim 27 , wherein the gaps have an average value equal to 70% of the value of the shortest wavelength and the pillars have an average height equal to one half the longest wavelength.

29. The non-linear optical crystal of claim 17 , wherein the non-linear optical crystal is a Lithium triborate (LBO) crystal.

30. The non-linear optical crystal of claim 17 , wherein the conformal moisture barrier layer shields the first structured optical surface from moisture.

31. The non-linear optical crystal of claim 17 , wherein the conformal moisture barrier layer has a refractive index matching the non-linear optical crystal.

32. The non-linear optical cr

Assignees

• Gamdan Optics Inc
• Univ Of North Carolina At Charlotte
• Univ North Carolina Charlotte

Inventors

• Poutous Menelaos K
• Cai Hui
• Gadamsetti Praneeth

Classifications

• C01P2006/60

  Optical properties, e.g. expressed in CIELAB-values · CPC title

• C01P2002/85

  by XPS, EDX or EDAX data · CPC title

• C01B35/121

  of alkali metal · CPC title

• G02F1/3551 Primary

  Crystals · CPC title