Silica-modified-fluoride broad angle antireflection coatings

Abstract

The disclosure is directed to a coating consisting of a binary metal fluoride coating consisting a high refractive index metal fluoride layer on top of a substrate, a low refractive index metal fluoride layer on top of the high refractive index layer and layer of SiO 2 or F—SiO 2 containing 0.2 wt % to 4.5 (2000 ppm to 45,000 ppm) F on top of the low refractive index layer. In one embodiment the F content of F—SiO 2 is in the range of 5000 ppm to 10,000 ppm F. The high index and low index materials are each deposited to a thickness of less than or equal to 0.9 quarter wave, and the capping material is deposited to a thickness in the range of 5 nm to 25 nm. The disclosure is also directed to optical elements having the foregoing coating and a method of making the coating.

1 .- 9 . (canceled) 
     
     
         10 . A method for making an optical element having a coating thereon, the method comprising
 providing a substrate selected from the group consisting of CaF 2 , SiO 2  and F—SiO 2 ,   applying a coating of a high refractive index metal fluoride material to the surface of the substrate using vacuum deposition at a temperate greater than or equal to 300° C., the reverse mask technique, and in-situ or post-deposition plasma ion treatment;   applying a coating of a low refractive index metal fluoride material to the surface of the high refractive index material using vacuum deposition at a temperate greater than or equal to 300° C., the reverse mask technique, and in-situ or post-deposition plasma ion treatment; and   depositing a capping layer selected from the group consisting of SiO 2  and F—SiO 2  on top of the low refractive index material using vacuum deposition at a temperate greater than or equal to 300° C., the reverse mask technique, and in-situ or post-deposition plasma ion treatment to thereby produce an optical element having a coating thereon;   wherein the high index and low index materials are each deposited to a thickness of f less than or equal to 0.9 quarter wave, and the capping material is deposited to a thickness in the range of 5 nm to 25 nm.   
     
     
         11 . The method according to  claim 10 , wherein the high refractive index coating material is selected from the group consisting of GdF 3  and LaF 3    
     
     
         12 . The method according to  claim 10 , wherein the low refractive index coating material is selected from the group consisting of AlF 3  and MgF 3 , 
     
     
         13 . The method according to  claim 10 , wherein the produced optical element is a mirror, lens, laser window or prism. 
     
     
         14 . The method according to  claim 10 , wherein the provided substrate is a F—SiO 2  substrate containing 0.5 wt. % to 4.5 wt. % F.