Micro optical fiber light source and sensor and method of fabrication thereof

• US 5,361,314 A
• Filed: 09/04/1992
• Issued: 11/01/1994
• Est. Priority Date: 09/04/1992
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Tan, Weihong, Kopelman, Raoul, Shi, Zhong-You
• Primary Examiner(s): Healy, Brian
• Application Number:
  US07/941,879
• Time in Patent Office: 788 Days
• Field of Search: 385/12, 385/125, 385/33, 385/43, 385/14, 385/31, 385/123, 385/38, 359/368, 359/385, 250/227.14, 250/227.18, 250/227.11, 427/162, 427/163, 427/457, 427/487
• US Class Current: 385/12
• 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: 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 6/2552 reshaping or reforming of light guides for coupling using thermal heating, e.g. tapering, forming of a lens on light guide ends
• CPC Class Codes: G02B 6/3624 Fibre head, e.g. fibre probe termination optical details of light guide terminations G02B6/241; reshaping of light guides G02B6/2552; optical details of coupling light into or out of fibre end G02B6/262

Abstract

This invention relates generally to the development of and a method of fabricating a micro optical fiber light source. An optical fiber micro-light source is presented whose aperture is extremely small yet able to act as an intense light source. Light sources of this type have wide ranging applications, including use as micro-sensors in NSOM. Micro-sensor light sources have excellent detection limits as well as photo stability, reversibility, and millisecond response times. Furthermore, a method for manufacturing a micro optical fiber light source is provided. It involves the photo-chemical attachment of an optically active material onto the end surface of an optical fiber cable which has been pulled to form an end with an extremely narrow aperture. More specifically, photopolymerization has been applied as a means to photo-chemically attach an optically active material. This process allows significant control of the size of the micro light source. Furthermore, photo-chemically attaching an optically active material enables the implementation of the micro-light source in a variety of sensor applications.

Claims

1. An optical fiber light source comprising an optical fiber having one end of said fiber substantially uniformly tapered to define a tapered portion of said optical fiber, said tapered portion being less than 10 micrometers in diameter and having an end face to further define an optical fiber tip, aid tapered portion also having sides coated with an opaque material to prevent the escape of light from said tapered portion, and an optically active material photo-chemically attached to said optical fiber tip, said optically active material inwardly tapering away from said optical fiber tip and having a size and shape in accordance with a duration and an intensity of light applied during said photo-chemical attachment process, and said optically active material being responsive to excitation by light.

2. The apparatus of claim 1 wherein said opaque material preventing the escape of light from the tapered portion of said optical fiber is a compound substantially comprised of a metal.

3. The apparatus of claim 1 wherein the optical fiber tip of said optical fiber light source is chemically activated before chemical attachment of the optically active material to said optical fiber tip to improve adherence.

4. The apparatus of claim 1 wherein said optically active material is chemically attached to said fiber optic tip using a photopolymerization process in which light is coupled into a non-tapered end of said optical fiber to enable fabrication of the optically active material to a desired size and shape in accordance with the duration and intensity of light associated with the photopolymerization process.

5. The apparatus of claim 4 wherein said photopolymerization process may occur repeatedly in order to photopolymerize substantially different chemically active materials.

6. The apparatus of claim 4 wherein said photopolymerization process may occur repeatedly in order to photopolymerize said optically active material onto said fiber optic tip in progressive steps.

7. The apparatus of claim 1 wherein said optically active material includes an illuminescent dye which is optically responsive to a particular environment.

8. A method of fabricating an optical fiber light source comprising:

pulling one terminal end of an optical fiber to form a taper having a diameter less than 10 micrometers at said terminal end of the optical fiber and an end surface of the tapered portion of said optical fiber to define a tip;

coating the tapered portion of said optical fiber with an opaque material which substantially prevents escape of light from the tapered portion of said optical fiber and directing said light toward the tip of said tapered end;

chemically activating the tip of said optical fiber to improve chemical attachment between said tip and an optically active material to be attached thereto;

photo-chemically attaching said optically active material to the chemically activated tip of said optical fiber to form an inwardly tapering probe tip of said optical fiber sensor, said inwardly tapering probe tip having a size and shape controlled by varying a duration and an intensity of light applied during said photo-chemical attachment process, and said optically active material being responsive to excitation by light.

9. The method described in claim 8 wherein chemically attaching said optically active material to the chemically activated tip of said optical fiber comprises photopolymerization in which light is coupled to the non-tapered end of said optical fiber and the size and shape of said optically activated material varies in accordance with said duration and intensity of light associated with said photopolymerization process.

10. The method described in claim 8 wherein photopolymerization onto the chemically activated tip of said optical fiber comprises coupling light of a given wavelength into the non-tapered end of said optical fiber to photopolymerize said optically active material onto said chemically activated surface wherein said coupled light photopolymerizes the optically active material to form said optically active material in a substantially conical shape.

11. A fiber optic light source sensor wherein said sensor includes:

an optical fiber including a first tapered terminal end and a tip as defined by an end face of the tapered optical fiber, said tip having a diameter less than 10 micrometers;

an optically active material photopolymerized for a duration with light having an intensity onto the tip of said tapered end in an inward taper and having a size and shape controlled by said duration and intensity of light of the photopolymerization process, said optically active material including a dye whose optical response varies in accordance with the particular condition to be sensed;

a light source coupled to a second non-tapered end of said optical fiber where said light source generates light of predetermined intensity and wavelength;

a means for disposing said optically active material of said optical fiber in close proximity to a sample;

an objective lens disposed in proximity to the optically active material of said optical fiber so that light emitted from said material is collected by said objective lens after interaction with the sample; and

a means for analyzing said light emissions absorbed by said objective lens.

12. A fiber optic light source sensor wherein said sensor includes:

an optical fiber including a first tapered terminal end and a tip as defined by the end face of the tapered optical fiber, said tip having a diameter less than 10 micrometers;

an optically active material photopolymerized for a duration with light having an intensity onto the tip of said tapered end forming an inward taper and having a size and shape controlled by said photopolymerization process, said optically active material including a dye whose optical response varies in accordance with the particular condition to be sensed;

a light source coupled to a second non-tapered end of said optical fiber where said light source generates light of predetermined intensity and wavelength;

a means for substantially continuously disposing said optically active material of said optical fiber in close proximity to a sample to effectuate a light emission varying in intensity and wavelength in accordance with said chemical interaction between said sample and said optically active material;

an objective lens disposed in proximity to the optically active material of said optic fiber so that light emitted from said material is collected by said objective lens after interaction with the sample; and

a means for analyzing said light emissions absorbed by said objective lens.