Optical elements with stress-balancing coatings

Patent metadata

Field	Value
Publication number	US-2018024276-A1
Application number	US-201715646883-A
Country	US
Kind code	A1
Filing date	Jul 11, 2017
Priority date	Jul 21, 2016
Publication date	Jan 25, 2018
Grant date	—

Abstract

Optical elements with coatings having low surface figure are described. The optical element includes coatings on two or more surfaces. At least one of the coatings includes a stress-compensating layer. In the absence of the stress-compensating layer, the coatings are mismatched in stress. The difference in stress increases surface figure and distorts the wavefront of optical signals that are reflected and/or transmitted through the optical element. The stress-compensating layer acts to reduce mismatch in stress and leads to coatings with reduced surface figure and reduced distortion of wavefronts.

First claim

What is claimed is:

1 . An optical element comprising:
a substrate, said substrate having a first surface and a second surface; a first coating on said first surface, said first coating having a first coating stress and including a first layer, said first layer comprising a first material, said first material having a first layer stress in said first layer; a second coating on said second surface, said second coating having a second coating stress and including a second layer, said second layer comprising said first material, said first material having a second layer stress in said second layer, said second layer stress being greater in magnitude than said first layer stress.

2 . The optical element of claim 1 , wherein said first coating is a beam splitting coating.

3 . The optical element of claim 2 , wherein said second coating is an antireflection coating.

4 . The optical element of claim 1 , wherein said first material comprises an oxide.

5 . The optical element of claim 1 , wherein said first layer stress is compressive and said second layer stress is compressive.

6 . The optical element of claim 5 , wherein said first coating stress is in the range from 75% to 125% of the second coating stress.

7 . The optical element of claim 1 , wherein said first coating further includes a third layer, said third layer comprising a second material, said second material differing in composition from said first material.

8 . The optical element of claim 1 , wherein said second coating further includes a third layer, said third layer comprising a second material, said second material differing in composition from said first material.

9 . The optical element of claim 8 , wherein said second material is a metal fluoride.

10 . The optical element of claim 1 , wherein said first coating includes a plurality of said first layers.

11 . The optical element of claim 10 , wherein said first coating further includes a plurality of third layers, each of said third layers comprising a second material, said second material differing in composition from said first material.

12 . The optical element of claim 11 , wherein said second coating further includes a fourth layer, said fourth layer comprising a third material, said third material differing in composition from said first material.

13 . The optical element of claim 12 , wherein said first material comprises an oxide and said third material comprises a metal fluoride.

14 . An optical element comprising:
a substrate, said substrate having a first surface and a second surface; a first coating on said first surface, said first coating including a first layer, said first layer comprising a first material, said first material having a first density in said first layer; a second coating on said second surface, said second coating including a second layer, said second layer comprising said first material, said first material having a second density in said second layer, said second density being greater than said first density.

15 . A method of forming an optical element comprising:
forming a first coating on a first surface of a substrate, said first coating having a first coating stress and including a first layer, said first layer including a first material, said first material having a first layer stress in said first layer; and forming a second coating on a second surface of said substrate, said second coating having a second coating stress and including a second layer, said second layer including said first material, said first material having a second layer stress in said second layer, said second layer stress being greater than said first layer stress.

16 . The method of claim 15 , wherein said first layer stress is compressive and said second layer stress is compressive.

17 . The method of claim 15 , further comprising controlling a thickness of said first material in said second layer to offset said first coating stress.

18 . The method of claim 15 , further comprising controlling said second layer stress to offset said first coating stress.

19 . The method of claim 15 , wherein said forming first coating further comprises forming a third layer, said third layer including a second material, said second material differing in composition from said first material.

20 . The method of claim 19 , wherein said forming second coating further comprises forming a fourth layer, said fourth layer comprising a third material, said third material differing in composition from said first material.

Assignees

• Corning Inc

Inventors

• Wang Jue

Classifications

• G02B27/142

  Coating structures, e.g. thin films multilayers · CPC title

• G02B1/115

  Multilayers · CPC title

• C23C14/32

  by explosion; by evaporation and subsequent ionisation of the vapours {, e.g. ion-plating}(C23C14/34 - C23C14/48 take precedence) · CPC title

• G02B1/14 Primary

  Protective coatings, e.g. hard coatings · CPC title

• C23C14/10

  Glass or silica · CPC title