Integrated fluorescene

• US 5,841,143 A
• Filed: 07/11/1997
• Issued: 11/24/1998
• Est. Priority Date: 07/11/1997
• Status: Expired due to Fees

• Current Assignee: Administrator of The National Aeronautics and Space Administration, National Aeronautics and Space Administration US Government As Represented By The Administrator of The
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Gruhlke, Russell W., Tuma, Margaret
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Jiron, Darren M.
• Application Number:
  US08/903,184
• Time in Patent Office: 501 Days
• Field of Search: 250/458.1, 250/459.1, 385/12, 385/37, 385/129, 385/130, 385/131
• US Class Current: 250/458.1
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/648 using evanescent coupling or surface plasmon coupling for the excitation of fluorescence

Abstract

A detection method is integrated with a filtering method and an enhancement method to create a fluorescence sensor (10) that can be miniaturized. The fluorescence sensor (10) comprises a thin film geometry including a waveguide layer (16), a metal film layer (20) and sensor layer (32). The thin film geometry of the fluorescence sensor allows the detection of fluorescent radiation over a narrow wavelength interval. This enables wavelength discrimination and eliminates the detection of unwanted light from unknown or spurious sources.

Claims

1. An article for analyzing fluorescence from a fluorescent material comprising:

fluorescent material in close proximity to a first surface of a dielectric waveguide layer,

wherein said waveguide layer supports waveguide modes at the wavelength of fluorescence and wavelength of absorption of said fluorescent material, wherein said waveguide modes penetrate into said fluorescent material and excite the fluorescence of said fluorescent material, whereby the fluorescence of said fluorescent material is enhanced;

a corrugated metal film layer positioned adjacent to a second surface of said waveguide layer, wherein said metal film layer supports a first plurality of plasmons positioned at the interface of said metal film layer and said adjacent waveguide layer, wherein each of said first plurality of plasmons is excited by all fluorescent wavelengths within said waveguide layer, and said first plurality of plasmons produces a first field,

a sensor layer, wherein said sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal,

wherein said metal film layer supports a second plurality of plasmons, wherein said second plurality of plasmons is positioned within said first plasmon field and is excited by said first plasmon field at a wavelength interval which includes the wavelength of fluorescence to produce a second plasmon field, wherein said second plasmon field penetrates said sensor layer,

whereby said sensor layer generates an electrical signal corresponding to the fluorescence intensity of the fluorescent material at the wavelength of fluorescence.

2. The article of claim 1, wherein said metal film layer is opaque to all wavelengths not within said wavelength interval.

3. The article of claim 1, further comprising a dielectric buffer layer, wherein said buffer layer is interposed between said sensor layer and said corrugated metal film layer.

4. The article of claim 3, wherein said second plurality of plasmons are positioned at the interface of said corrugated metal film layer and said buffer layer.

5. The article of claim 3, wherein said buffer layer has a uniform thickness across parallel planes which extend parallel with the surface of said metal film layer.

6. The article of claim 1, wherein said waveguide layer has a uniform thickness across parallel planes which extend parallel with the surface of said metal film layer.

7. The article of claim 1, wherein said sensor layer comprises a semiconductor pn junction, wherein said semiconductor pn junction is positioned within said second plasmon field.

8. The article of claim 1, wherein a first area of said metal film layer is corrugated at a first periodicity, wherein a second area of said metal film layer is corrugated at a second periodicity.

9. The article of claim 1, wherein each of the surfaces of said corrugated metal layer comprises a sinusoidal surface relief characterized by peak to valley distances of approximately 50 nanometers and by periodicity of the order of one micron.

10. An article for analyzing the fluorescence from a fluorescent material comprising:

a fluorescent material layer;

a dielectric layer;

a metal film layer positioned in optical communication with said dielectric layer, wherein said metal film layer supports a first plasmon, wherein said first plasmon produces a first field when excited by fluorescence from said fluorescent material layer, wherein said metal film layer supports a second plasmon, wherein said second plasmon is positioned within said first field and is excited by said first field at a wavelength interval which includes said wavelength of fluorescence to produce a second field, whereby a decay pathway for the fluorescence from said fluorescent material layer at said fluorescent wavelength is produced;

a sensor layer, wherein said second field penetrates said sensor layer, whereby said sensor layer absorbs optical energy from said second field and generates a signal corresponding to the fluorescence of the fluorescent material at the wavelength of fluorescence.

11. The article of claim 10, wherein said dielectric layer supports waveguide modes for optical radiation at said wavelength of fluorescence and wavelength of absorption of said fluorescent material, wherein said waveguide modes penetrate into said fluorescent material layer and excite the fluorescence of said fluorescent material, whereby the fluorescence of said fluorescent material is enhanced.

12. The article of claim 10, wherein a first area of said metal film layer is corrugated with a first periodicity, wherein said first area is transparent to all wavelengths within said wavelength interval.

13. The article of claim 12, wherein a second area of said metal film layer is corrugated with a second periodicity, wherein said second-area is transparent to all wavelengths within a second wavelength interval.

14. The article of claim 13, wherein said dielectric layer supports waveguide modes for optical radiation at said wavelength of fluorescence and wavelength of absorption of said fluorescent material, wherein said waveguide modes penetrate into said fluorescent material layer and excite the fluorescence of said fluorescent material, whereby the fluorescence of said fluorescent material is enhanced.

15. The article of claim 14, wherein said metal film layer is opaque to all wavelengths not within said wavelength interval, whereby the noise received by said sensor is reduced.

16. The article of claim 10, wherein said metal film layer is opaque to all wavelengths not within said wavelength interval, whereby the noise received by said sensor is reduced.

17. The article of claim 10, wherein said sensor layer comprises a semiconductor pn junction, wherein said semiconductor pn junction is positioned within said second field, and wherein said signal is electrical.

18. The article of claim 10, wherein said dielectric layer is bounded by said metal film layer and said fluorescent material layer, wherein said first plasmon is positioned at the interface of said dielectric layer and said metal film layer.

19. The article of claim 10, further comprising a buffer layer, wherein said buffer layer comprises a dielectric material, wherein said buffer layer is interposed between said sensor layer and said metal film layer, wherein said second plasmon is supported at the interface of said buffer layer and said metal film layer.

20. A method of detecting the fluorescence of a material comprising the steps of:

creating a sensor by depositing a thin film stack onto a sensing layer, wherein said sensing layer is operative to absorb fluorescence and generate an electrical signal corresponding to the strength of said fluorescence, wherein said thin film stack comprises a plurality of layers, said plurality of layers including;

a layer of electrically conductive, opaque material disposed over the sensing layer, comprising a plurality of plasmons on the surfaces of said layer, wherein said plasmons operate to allow a decay pathway for the fluorescence of said material,

a layer of dielectric material disposed over said electrically conductive layer, wherein said layer of dielectric material supports waveguide modes for optical radiation at the wavelength of absorption by and fluorescence from said material;

placing said sensor in close proximity with said material;

detecting the fluorescence of said material by monitoring said electrical signal from said sensing layer to determine the amount of fluorescence emanating,. from said material and passing through said layer dielectric material to said sensing layer.

21. The method of claim 20 wherein said waveguide modes excite said material to fluoresce whereby there is enhanced fluorescence from said material.

22. The method of claim 20 wherein a film of said material is deposited on a surface of said waveguide.

23. The method of claim 20 further comprising the step of corrugating a first area of said electrically conductive layer with a first periodicity.

24. The method of claim 23 further comprising the step of corrugating a second area of said electrically conductive layer with a second periodicity.

25. The method of claim 20 wherein said sensor layer, said electrically conductive layer and said dielectric material layer all have parallel surfaces.

26. The method of claim 20 wherein said waveguide modes are excited by incident light.

27. The method of claim 26 wherein said incident light is from a laser.

28. The method of claim 20 wherein said waveguide modes are excited by incident light of TM or TE polarization.

29. The method of claim 20, wherein said sensor layer comprises a semiconductor pn junction and said electrical signal is a current signal.

30. The method of claim 20, wherein said plasmons positioned on the surface of said electrically conductive layer adjacent said dielectric layer are excited by said waveguide modes.

31. The method of claim 20, wherein said plasmons positioned on the surface of said electrically conductive layer adjacent said dielectric layer are excited by said fluorescing material.