Chemical etching of fiber probe

• US 5,985,166 A
• Filed: 10/29/1997
• Issued: 11/16/1999
• Est. Priority Date: 10/29/1997
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Unger, Marc A., Kossakovski, Dmitri A.
• Primary Examiner(s): Breneman, Bruce
• Assistant Examiner(s): Ahmed, Shamim
• Application Number:
  US08/960,034
• Time in Patent Office: 748 Days
• Field of Search: 216/11, 216/24, 216/96, 216/97, 216/108, 216/109
• US Class Current: 216/97
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: C03C 25/68 by etching
• CPC Class Codes: G01Q 60/22 Probes, their manufacture, or their related instrumentation, e.g. holders
• CPC Class Codes: G02B 6/241 Light guide terminations
• CPC Class Codes: G02B 6/245 Removing protective coverings of light guides before coupling
• CPC Class Codes: Y10S 977/881 Microscopy or spectroscopy, e.g. sem, tem
• CPC Class Codes: Y10S 977/889 by laser ablation

Abstract

A two-phase etching system having an etchant solution and an overlayer of a protective solvent. The physical properties of the etchant solution and the protective solvent are matched to form a substantially flat meniscus on the top surface of the etchant solution around a fiber immersed in the protective solvent and the etchant solution. Convective flows within the etchant solution are maintained to form a smooth and sharp fiber probe with a small tip apex.

Claims

1. A method of etching a fiber, comprising:

providing an etchant solution which is chemically reactive to the fiber and has a first interfacial energy with respect to the fiber;

forming a layer of a protective solvent that is chemically inert to the fiber on top of said etchant solution, said protective solvent having a density smaller than said etchant solution and having a second interfacial energy with respect to the fiber, wherein said first interfacial energy is substantially equal to said second interfacial energy;

immersing a portion of the fiber in said etchant solution and said protective solvent; and

maintaining convective flows surrounding said immersed portion within said etchant solution so that said immersed portion is broken away by etching to form a tapered tip within said etchant solution.

2. A method as in claim 1, wherein said etchant solution includes a mixture of an oxidizing acid and a hydrogen peroxide.

3. A method as in claim 1, wherein said protective solvent is a solution having a chemical material selected from a group consisting of tetramethylpentadecane (TMPD), polydimethylsiloxane (PDMS), and CCl₄.

4. A method as in claim 2, wherein said etchant solution is an approximately 7:

3 mixture by volume of concentrated sulfuric acid and a hydrogen peroxide of 30% water solution.

5. A method as in claim 1, wherein the immersing step comprises holding the fiber in said etchant solution and said protective solvent in a substantially vertical orientation.

20. A method as in claim 1, wherein the fiber comprises a chalcogenide glass.

6. A method of etching a fiber, comprising:

providing an etchant solution which is chemically reactive to the fiber;

forming a layer of a protective solvent that is chemically inert to the fiber on top of said etchant solution and having a density smaller than said etchant solution,

selecting said etchant solution and said protective solvent to have predetermined densities and viscosity coefficients to form a substantially flat meniscus on the interface between said etchant solution and protective solvent around the fiber when immersed;

immersing a portion of the fiber in said etchant solution and said protective solvent; and

maintaining convective flows surrounding said immersed portion within said etchant solution so that said immersed portion is broken away by etching to form a tapered tip within said etchant solution.

7. A method as in claim 6, wherein said etchant solution includes a mixture of an oxidizing acid and a hydrogen peroxide.

8. A method as in claim 6, wherein said protective solvent is a solution having a chemical material selected from a group consisting of tetramethylpentadecane (TMPD), polydimethylsiloxane (PDMS), and CCl₄.

9. A method as in claim 7, wherein said etchant solution is an approximately 7:

3 mixture by volume of concentrated sulfuric acid and a hydrogen peroxide of 30% water solution.

10. A method as in claim 6, wherein the immersing step comprises holding the fiber in said etchant solution and said protective solvent in a substantially vertical orientation.

21. A method as in claim 6, wherein the fiber comprises a chalcogenide glass.

11. A method of forming a chalcogenide fiber probe by chemical etching, comprising:

processing a fiber having a chalcogenide fiber core to expose the fiber core at one end;

providing an etchant solution which is chemically reactive to said fiber core and has a first interfacial energy with respect to said fiber core;

forming a layer of a protective solvent chemically inert to said fiber core on top of said etchant solution, said protective solvent having a density smaller than said etchant solution and a second interfacial energy with respect to said fiber core, wherein said first interfacial energy is substantially equal to said second interfacial energy;

immersing said fiber core in said etchant solution and said protective solvent; and

maintaining convective flows surrounding said immersed fiber core within said etchant solution so that a portion of said fiber core is broken away by etching at a location below interface between said protective solvent and etchant to form a tapered probe tip within said etchant solution.

12. A method as in claim 11, wherein the step of processing the fiber to expose the fiber core comprises removing polymer coating and fiber cladding outside the fiber core.

13. A method as in claim 12, wherein said polymer coating is removed by immersing the fiber in 4-chloro-1-butanol, methanol, or acetone.

14. A method as in claim 12, wherein said fiber cladding is SSe which is removed by immersing the clad fiber in a NaOH solution after said polymer coating is removed.

15. A method as in claim 11, wherein said etchant solution includes a mixture of an oxidizing acid and a hydrogen peroxide.

16. A method as in claim 11, wherein said protective solvent is a solution having a chemical material selected from a group consisting of tetramethylpentadecane (TMPD), polydimethylsiloxane (PDMS), and CCl₄.

17. A method as in claim 15, wherein said etchant solution is an approximately 7:

3 mixture by volume of concentrated sulfuric acid and a hydrogen peroxide of 30% water solution.

18. A method as in claim 11, wherein the immersing step comprises holding the fiber in said etchant solution and said protective solvent in a substantially vertical orientation.

19. A method as in claim 11, further comprising:

removing the fiber from said etchant solution and said protective solvent after an immersed portion of said fiber core falls off from the fiber; and

washing the fiber with a cleansing solution to remove residual of the etchant solution from the fiber.