Sensors

• US 20080158563A1
• Filed: 08/20/2007
• Published: 07/03/2008
• Est. Priority Date: 08/21/2006
• Status: Abandoned Application

• Current Assignee: Spectalis Corp.
• Original Assignee: Spectalis Corp.
• Inventors: Charbonneau, Robert, Berini, Pierre Simon Joseph, Lahoud, Nancy
• Application Number:
  US11/892,062
• Publication Number:
  US 20080158563A1
• Time in Patent Office: Days
• US Class Current: 356/437
• CPC Class Codes: G01N 2021/7779 interferometric
• CPC Class Codes: G01N 21/7703 using reagent-clad optical fibres or optical waveguides using measurement of total internal reflection or attenuated total reflection G01N21/552; optical fibres or waveguides per se G02B

Abstract

A gas sensor for hydrogen or other gases, especially flammable or explosive gases, has a plasmon-polariton waveguide comprising a metal strip on a membrane supported by a substrate in an environment in which the gas is to be introduced, and coupling means for coupling optical radiation into and out of the plasmon-polariton waveguide such that the optical radiation propagates therealong as a plasmon-polariton wave. The metal strip comprises by a chemical transducer (e.g. Pd or PdNi), the arrangement being such that exposure of the metal strip or coating to the gas to be monitored causes a change in the propagation characteristics of the plasmon-polariton wave and hence the optical radiation coupled out of the plasmon-polariton waveguide.

Claims

1. A gas sensor having a plasmon-polariton waveguide comprising a metal strip on a membrane supported by a substrate in an environment in which the gas to be sensed may be present, input means for coupling optical radiation into the plasmon-polariton waveguide such that the optical radiation propagates therealong as a plasmon-polariton wave and output means for receiving said optical radiation following said propagation, the metal strip comprising a chemical transducer, the arrangement being such that exposure of the chemical transducer to the gas to be sensed causes a change in the propagation characteristics of the plasmon-polariton wave propagating along the waveguide and hence a change in the optical radiation coupled out of the plasmon-polariton waveguide, the output means comprising means for monitoring for a change in said propagated optical radiation consistent with the presence of a prescribed level of the gas in the environment contacting the transducer.

2. A gas sensor according to claim 1, wherein the chemical transducer comprises palladium or a palladium-based alloy, such as palladium-nickel.

3. A gas sensor according to claim 1, wherein the strip has a surface layer of said chemical transducer, e.g., as an adlayer.

4. A gas sensor according to claim 1, for use in sensing an analyte of, for example, a chemical nature, wherein the chemical transducer material i.e., adlayer, comprises receptors for binding with the analyte.

5. A sensor according to claim 1, wherein the membrane means extends between spaced supports.

6. A gas sensor according to claim 1, wherein the membrane covers a surface of the strip and is substantially non-invasive optically.

7. A sensor according to claim 1, wherein the membrane means is permeable, apertured, porous or otherwise configured so as to allow the gas to contact the chemical transducer through the membrane means.

8. A gas sensor according to claim 7, wherein the membrane (14) has a plurality of apertures (26) spaced apart along its length, said juxtaposed portion of the strip comprising parts (28) of the strip exposed through respective ones of said apertures, and margin portions (30) of the strip (12) around the exposed parts (28) overlie and are attached to respective parts (32) of the membrane (14).

9. A gas sensor according to claim 8, wherein the exposed parts (28) of the strip each extend into the respective one of the apertures (26).

10. A gas sensor according to claim 1, wherein the material of the membrane structure (14) comprises an optical dielectric selected, for example, from a group including glass, quartz, polymer, SiO2, Si3N4, silicon oxynitride (SiON), LiNbO3, PLZT, and undoped or very lightly doped semiconductors such as GaAs, InP, Si and Ge.

11. A gas sensor according to claim 10, wherein the material of the membrane structure (14) comprises SiO2, SiON or Si3N4.

12. A gas sensor according to claim 10, wherein the material of the membrane structure (14) is a polymer selected from the group comprising BCB, polyimide, PMMA, Teflon AF (TM), SU8.

13. A gas sensor according to claim 1, further comprising means (16) for confining adjacent at least one side of said strip (12) at least a part of said environment (E) that comprises either a vacuum or a gas and means for admitting the gas to be sensed into the confined environment and the membrane means (14) supports said strip (12) such that the chemical transducer extends at least partially within the confined environment.

14. A gas sensor according to claim 13, wherein the confining means comprises a channel (16) and the membrane means (14) divides the channel longitudinally into two cavities (16′

, 16″

), the strip (12) extending longitudinally and medially along the membrane means.

15. A gas sensor according to claim 1, wherein the input means comprises means (20) for coupling input optical radiation in an endfire manner to one end of said strip (12) so as to propagate along said strip as said plasmon-polariton wave.

16. A gas sensor according to claim 15, wherein the input coupling means comprises a polarization maintaining fiber (PMF) for inputting said optical radiation from a source thereof into said plasmon-polariton waveguide.

17. A gas sensor according to claim 1, wherein the input means comprises means (20,60) for coupling input optical radiation laterally to said strip (12) to propagate along said strip as said plasmon-polariton wave.

18. A gas sensor according to claim 1, wherein the output means comprises a single mode fiber for conveying optical radiation out of the plasmon-polariton waveguide to said monitoring means.

19. A gas sensor according to claim 1, wherein the output means comprises means for conveying optical radiation from the plasmon-polariton waveguide to monitoring means located nearby, for example within the same compact module, or at a remote location, such as in another building.

20. A gas sensor according to claim 1, wherein the output means comprises means (22) for extracting at least part of said plasmon-polariton wave in an endfire manner at an opposite end of said strip (12).

21. A gas sensor according to claim 15, wherein the output means comprises means (22,62) for extracting at least part of said plasmon-polariton wave laterally from said strip.

22. A gas sensor according to claim 15, wherein said monitoring means comprises first and second detectors whose respective electrical outputs are connected to a measuring unit, and wherein the input coupling means comprises a coupler having one output connected to an input end of the first plasmon-polariton waveguide and a second output connected to an input end of a second plasmon-polariton waveguide that is insensitive to said gas to be sensed, respective other ends of the first and second plasmon-polariton waveguides being connected to first and second detection means, respectively.

23. A gas sensor according to claim 15, wherein said monitoring means comprises first and second detectors whose respective electrical outputs are connected to a measuring unit, and wherein the input coupling means comprises a Y-junction having its leg connected to receive the optical radiation, one output connected to an input end of the first plasmon-polariton waveguide and a second output connected to an input end of a second plasmon-polariton waveguide that is insensitive to said gas to be sensed, respective other ends of the first and second plasmon-polariton waveguides being connected to first and second detection means, respectively.

24. A gas sensor according to claim 18, wherein the first plasmon-polariton waveguide has a strip comprising PD_0.92 Ni₀₈ and the second plasmon-polariton waveguide has a strip comprising Pd_0.44 Ni_0.56.

25. A gas sensor according to claim 15, wherein the input means comprises coupling means for coupling said optical radiation into the leg of a Y-junction having its branch arms connected to, respectively, input ends of the first-mentioned plasmon-polariton waveguide and a second, similar plasmon-polariton waveguide, but having no chemical transducer, respective opposite ends of the first and second plasmon-polariton waveguides being connected to respective branch arms of a second Y-junction whose leg is connected to a detector having its electrical output applied to said measuring means.

26. A gas sensor according to claim 15, wherein the input means comprises coupling means for coupling said optical radiation into the leg of a Y-junction having its branch arms connected to, respectively, input ends of the first-mentioned plasmon-polariton waveguide and a second, similar plasmon-polariton waveguide, but having no chemical transducer, respective opposite ends of the first and second plasmon-polariton waveguides being connected to respective inputs of a four-port coupler (115) whose corresponding outputs are coupled to first and second detector having their respective electrical signals applied to said measuring means.

27. A gas sensor according to claim 15, wherein the input means comprises coupling means for coupling said optical radiation into the leg of a Y-junction having its branch arms connected to, respectively, input ends of the first-mentioned plasmon-polariton waveguide and a second, similar plasmon-polariton waveguide that is insensitive to said gas to be sensed, respective opposite ends of the first and second plasmon-polariton waveguides being connected to respective inputs of a triple-out coupler (116) whose three outputs are connected to, respectively, first, second and third detectors having their respective electrical outputs coupled to said measuring means.

28. A gas sensor according to claim 25, wherein the first plasmon-polariton waveguide has a strip comprising PD_0.92 Ni₀₈ and the second plasmon-polariton waveguide has a strip comprising Pd_0.44Ni_0.56.

29. A gas sensor according to claim 1, and having materials and dimensions as set out in any one of Examples 1 to 22 described in this specification.