SUPPORT FOR REFLECTIVE OPTICAL ELEMENT

• US 20200132894A1
• Filed: 10/11/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Application

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Stephens, Shane Matthew, Tsan, John Pung, Wamboldt, Leonard Gerard, Woodard, Kenneth Smith
• Application Number:
  US16/599,567
• Publication Number:
  US 20200132894A1
• Time in Patent Office: Days
• CPC Class Codes: C23C 14/165 by cathodic sputtering
• CPC Class Codes: C23C 14/34 Sputtering
• CPC Class Codes: C23C 14/352 using more than one target C23C14/56 takes precedence
• CPC Class Codes: C23C 14/588 by mechanical treatment
• CPC Class Codes: C23C 14/5886 Mechanical treatment involving removal of material C23C14/588
• CPC Class Codes: G02B 1/14 Protective coatings, e.g. hard coatings
• CPC Class Codes: G02B 5/0808 having a single reflecting layer G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 7/182 for mirrors

Abstract

A support for optical elements is described. The support includes a base substrate with high specific stiffness and a finishing layer. The base substrate is Al, an alloy of Al, Mg, or an alloy of Mg. The finishing layer is preferably an alloy of Al and Si. The finishing layer is or is capable of being processed to provide a surface with low finish. Low finish is achieved by diamond turning or polishing the finishing material. The finishing layer has a coefficient of thermal expansion similar to the coefficient of thermal expansion of the base substrate. The optical element optionally includes a reflective stack on the finishing layer.

Claims

1. An optical element comprising:

a base substrate, the base substrate comprising Al, an alloy of Al, Mg, or an alloy of Mg; and

a finishing layer in contact with the base substrate, the finishing layer comprising a binary alloy of Al and Si.

2. The optical element of claim 1, wherein the base substrate has a first coefficient of thermal expansion and the finishing layer has a second coefficient of thermal expansion, the second coefficient of thermal expansion being within ±

5% of the first coefficient of thermal expansion.

3. The optical element of claim 1, wherein the base substrate comprises at least 90 wt % Al.

4. The optical element of claim 1, wherein the base substrate comprises at least 90 wt % Mg.

5. The optical element of claim 1, wherein the binary alloy comprises greater than 85.0 wt % Al and at least 0.5 wt % Si.

6. The optical element of claim 1, wherein the binary alloy comprises greater than 85.0 wt % Al and at least 5.0 wt % Si.

7. The optical element of claim 1, wherein the binary alloy comprises less than 75.0 wt % Al and greater than 25.0 wt % Si.

8. The optical element of claim 1, wherein the binary alloy comprises less than 50.0 wt % Al and greater than 50.0 wt % Si.

9. The optical element of claim 1, wherein the binary alloy is amorphous.

10. The optical element of claim 1, wherein the finishing layer comprises a surface with a finish less than 20 Å

RMS (root-mean-square) roughness as measured by interferometry or atomic force microscopy.

11. The optical element of claim 1, wherein the finishing layer comprises a surface with a finish less than 10 Å

RMS (root-mean-square) roughness as measured by interferometry or atomic force microscopy.

12. The optical element of claim 1, wherein the finishing layer includes crystalline grains.

13. The optical element of claim 12, wherein the crystalline grains are characterized by a histogram having less than 10% of grains with a size greater than 10 μ

m.

14. The optical element of claim 12, wherein at least 90% of the crystalline grains are oriented along the [111] crystal axis.

15. The optical element of claim 1, further comprising a reflective layer in contact with the finishing layer, the reflective layer comprising a metal or a metal alloy, the metal or metal alloy comprising an element selected from the group consisting of Ag, Au, Al, Rh, Cu, Pt and Ni.

16. A method of forming an optical element comprising:

forming a finishing layer on a base substrate, the finishing layer comprising a binary alloy of Al and Si, the base substrate comprising Al or Mg.

17. The method of claim 16, wherein the base substrate comprises at least 90 wt % Al and the finishing layer comprises greater than 85 wt % Al and greater than 0.5 wt % Si.

18. The method of claim 16, wherein the forming comprises sputtering a first target and a second target, the first target comprising Al and the second target comprising Si.

19. The method of claim 16, further comprising processing the finishing layer, the processing comprising diamond turning the finishing layer.

20. The method of claim 16, further comprising forming a reflective coating on the finishing layer.