Low polarization sensitivity gold mirrors on silica

• US 5,864,425 A
• Filed: 09/18/1996
• Issued: 01/26/1999
• Est. Priority Date: 12/15/1994
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Filas, Robert William
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US08/715,134
• Time in Patent Office: 860 Days
• Field of Search: 359/360, 359/487, 359/584, 359/585, 359/589, 359/883, 359/884, 359/629, 359/634, 385/31, 385/85, 385/119, 385/38
• US Class Current: 359/360
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 5/08 Mirrors vehicle mirrors involving special optical features B60R1/08
• CPC Class Codes: G02B 5/0875 the reflecting layers comprising two or more metallic layers
• CPC Class Codes: G02B 6/02052 comprising optical elements other than gratings, e.g. filters comprising gratings G02B6/02057
• CPC Class Codes: G02B 6/02057 comprising gratings
• CPC Class Codes: G02B 6/241 Light guide terminations
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres

Abstract

Gold is useful for infrared polarization-insensitive mirrors on silica. However, gold does not adhere to bare silica. The adherence is enhanced by depositing an optically thin glue layer of Ni-P on a silica surface after sensitization of the surface with SnF₂ and activation with PdCl₂ /HCl. The Ni-P layer is deposited in a thickness sufficient to enhance adherence of gold to the surface of silica but insufficient to act as a barrier to the passage of infrared radiation to or from the gold layer. One measure of the Ni-P thickness is the absorbance of the glue layer of >0.008 at 550 nm (>0.003 at 850 nm) as measured by a spectrophotometer. A 100-150 nm thick gold layer, deposited by e-beam deposition on this adhesion layer, adheres well enough to pass the commonly used "Scotch tape adhesion test". The ability to make gold adhere to silica with very low optical loss is useful in fabrication of lightwave devices which require the use of reflecting surfaces, such as on optical fibers or waveguides.

Claims

1. A gold mirror for reflecting radiation to or from a silica article comprising:

a silica article including a surface;

a gold layer; and

a nickel layer, said nickel layer forming an adhesion layer between said surface of said silica article and said gold layer;

wherein said nickel layer is deposited on said surface of said silica article by electroless plating, and said nickel layer has a thickness such that said nickel layer is substantially transparent to infrared radiation; and

wherein said nickel layer further comprises a nickel-phosphorus (Ni-P) alloy.

2. The gold mirror of claim 1, wherein said surface of said silica article is activated with Pd so as to form a Pd/Ni-P layer after deposition of said nickel-phosphorus (Ni-P) alloy.

3. The gold mirror of claim 2, in which said Pd/Ni-P layer is of a thickness such that its absorbance ranges from about 0.008 to 0.030 at 550 nm wavelength as measured by a spectrophotometer.

4. The gold mirror of claim 1, wherein said nickel layer has an absorbance of 0.01 at 550 nm.