Wavelength tunable surface plasmon resonance sensor

• US 20040130723A1
• Filed: 10/28/2003
• Published: 07/08/2004
• Est. Priority Date: 10/28/2002
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Yager, Paul, Fu, Elain S.
• Granted Patent: US 7,030,989 B2
• Time in Patent Office: Days
• US Class Current: 356/445
• CPC Class Codes: G01N 21/553 and using surface plasmons fluorescence excitation G01N21/648; enhanced Raman G01N21/658
• CPC Class Codes: G01N 21/648 using evanescent coupling or surface plasmon coupling for the excitation of fluorescence

Abstract

This invention provides methods, devices and device components for sensing, imaging and characterizing changes in the composition of a probe region. More particularly, the present invention provides methods and devices for detecting changes in the refractive index of a probe region positioned adjacent to a sensing surface, preferably a sensing surface comprising a thin conducting film supporting surface plasmon formation. In addition, the present invention provides methods and device for generating surface plasmons in a probe region and characterizing the composition of the probe region by generating one or more surface plasmon resonances curves and/or surface plasmon resonance images of the probe region.

Claims

1. A surface plasmon resonance sensor for sensing the refractive index of a probe region comprising:

a polychromatic light source for generating light propagating along an incident light propagation axis;

a polarizer in optical communication with said polychromatic light source for selecting the polarization state of said light;

an optical assembly in optical communication with said polychromatic light source, said optical assembly comprising a dielectric layer, a dielectric sample layer and a conducting layer positioned between said dielectric layer and said dielectric sample layer, wherein illumination of said optical assembly with said light generates light propagating along a reflected light propagation axis, wherein a portion of said dielectric sample layer adjacent to said conducting film comprises the probe region;

a detector in optical communication with said optical assembly for detecting said light propagating along said reflected light axis, thereby sensing the refractive index of said probe region; and

a selectably adjustable wavelength selector positioned in the optical path between said light source and said detector for transmitting light having a distribution of transmitted wavelengths selected to generate surface plasmons on a surface of said conducting layer in contact with said dielectric sample layer.

2. The surface plasmon resonance sensor of claim 1 further comprising a light collection and focusing element positioned between said optical assembly and said detector, said light collection and focusing element for collecting said light propagating along the reflected light propagation axis and focusing light propagating along the reflected light propagation axis onto said detector.

3. The surface plasmon resonance sensor of claim 1 further comprising a collimating optical element for collimating light from said polychromatic light source, wherein said collimating optical element is positioned between said polychromatic light element and said optical assembly.

4. The surface plasmon resonance sensor of claim 3 where said collimating optical element comprises a first lens, a pinhole, and a second lens each positioned between said polychromatic light source and said optical assembly.

5. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector is positioned between said optical assembly and said detector.

6. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector is positioned between said polychromatic light source and said optical assembly.

7. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector is an optical interference filter.

8. The surface plasmon resonance sensor of claim 7 wherein said optical interference filter is a Fabry-Perot etalon.

9. The surface plasmon resonance sensor of claim 7 wherein said optical interference filter is a linear variable interference filter.

10. The surface plasmon resonance sensor of claim 7 wherein said optical interference filter is rotationally adjustable about an axis which is orthogonal to said incident light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of transmitted wavelengths.

11. The surface plasmon resonance sensor of claim 10 wherein rotation of said optical interference filter selectably adjusts the center wavelength of the distribution of transmitted wavelengths.

12. The surface plasmon resonance sensor of claim 11 wherein said center wavelength of the distribution of transmitted wavelengths is provided by the equation:

13. The surface plasmon resonance sensor of claim 7 wherein said optical interference filter is rotationally adjustable about an axis which is orthogonal to said reflected light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of transmitted wavelengths.

14. The surface plasmon resonance sensor of claim 13 wherein rotation of said optical interference filter selectably adjusts the center wavelength of the distribution of transmitted wavelengths.

15. The surface plasmon resonance sensor of claim 14 wherein said center wavelength of the distribution of transmitted wavelengths is provided by the equation:

16. The surface plasmon resonance sensor of claim 7 wherein said optical interference is rotationally adjustable about an axis which is orthogonal to said incident light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths that are substantially prevented from transmitting through said optical interference filter.

17. The surface plasmon resonance sensor of claim 7 wherein said optical interference is rotationally adjustable about an axis which is orthogonal to said reflected light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths that are substantially prevented from transmitting through said optical interference filter.

18. The surface plasmon resonance sensor of claim 7 wherein said optical interference filter has first and second substantially parallel ends and said first end has a tilt angle selected over the range of 0°

to about 35°

.

19. The surface plasmon resonance sensor of claim 1 wherein said distribution of transmitted wavelengths is characterized by a center wavelength and said center wavelength is tunable over a range of about 65 nm.

20. The surface plasmon resonance sensor of claim 1 wherein said distribution of transmitted wavelengths is characterized by a bandwidth and said band width has a value selected from the range of about 1 nm to about 100 nm.

21. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector comprises a monochromator.

22. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector comprises a spectrometer.

23. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector comprises a prism.

24. The surface plasmon resonance sensor of claim 1 wherein said selectably adjustable wavelength selector comprises a grating.

25. The surface plasmon resonance sensor of claim 1 wherein said detector is a charge coupled device.

26. The surface plasmon resonance sensor of claim 1 wherein said dielectric layer has a first refractive index, wherein said dielectric sample layer has a second refractive index which is less than said first refractive index and wherein said light propagating along said incident light propagation axis undergoes total internal reflection upon interaction with said optical assembly.

27. The surface plasmon resonance sensor of claim 1 wherein said dielectric layer is a prism.

28. The surface plasmon resonance sensor of claim 1 further comprising a flow cell operationally connected to said optical assembly for introducing a sample into said probe region.

29. The surface plasmon resonance sensor of claim 28 wherein said dielectric sample layer is a sample provided by said flow cell.

30. The surface plasmon resonance sensor of claim 1 wherein said conducting layer comprises a gold film.

31. The surface plasmon resonance sensor of claim 1 wherein said first refractive index layer and said conducting layer comprise a waveguide.

32. The surface plasmon resonance sensor of claim 1 wherein said first refractive index layer and said conducting layer comprise an optical fiber.

33. The surface plasmon resonance sensor of claim 1 comprising a surface plasmon imaging device.

34. The surface plasmon resonance sensor of claim 1 wherein said light source is an incoherent light source.

35. The surface plasmon resonance sensor of claim 1 further comprising a microfluidic flow cell operationally connected to said optical assembly for introducing a sample into said probe region.

36. The surface plasmon resonance sensor of claim 35 wherein said surface of said conducting layer in contact with said second layer comprises a side of said microfluidic flow cell.

37. The surface plasmon resonance sensor of claim 1 wherein said surface of said conducting layer is modified to provide for selective binding affinity.

38. The surface plasmon resonance sensor of claim 1 wherein said surface of said conducting layer in contact with said dielectric sample layer is modified to provide for selective adsorption characteristics.

39. A method of sensing the refractive index of a probe region comprising the steps of:

passing light from a polychromatic light source through a polarizer, thereby generating light propagating along an incident light propagation axis;

directing said light onto an optical assembly, said optical assembly comprising a dielectric layer, a dielectric sample layer and a conducting layer positioned between said dielectric layer and said dielectric sample layer, thereby generating light propagating along a reflected light propagation axis, wherein a portion of said dielectric sample layer adjacent to said conducting layer comprises said probe region;

passing said light through a selectably adjustable wavelength selector positioned in the optical path between said light source and a detector;

detecting said light with said detector, thereby sensing said refractive index of said probe region, and

adjusting said selectably adjustable wavelength selector to transmit light having a distribution of wavelengths selected to generate surface plasmons on a surface of said conducting layer in contact with said dielectric sample layer.

40. The method of claim 39 wherein said adjusting step comprises the step of systematically varying said distribution of wavelengths transmitted by said selectably adjustable wavelength selector.

41. The method of claim 39 wherein said adjusting step comprises the steps of:

transmitting light through said selectably adjustable wavelength selector having a first distribution of wavelengths, thereby generating a first image of said probe region;

transmitting light through said selectably adjustable wavelength selector having a second distribution of wavelengths, thereby generating a second image of said probe region;

comparing the spectral quality of said first and second images; and

selecting a distribution of wavelengths of said incident light which are transmitted by said selectably adjustable wavelength selector to enhance the spectral quality of said image.

42. The method of claim 39 wherein said selectably adjustable wavelength selector is positioned between said light source and said optical assembly.

43. The method of claim 39 wherein said selectably adjustable wavelength selector is positioned between said optical assembly and said detector.

44. The method of claim 39 wherein said selectably adjustable wavelength selector is an optical interference filter.

45. The method of claim 44 wherein said optical interference filter is a Fabry-Perot etalon.

46. The method of claim 44 wherein said adjusting step comprises the step of rotating said optical interference filter about an axis which is orthogonal to said incident light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths of light which are transmitted.

47. The method of claim 44 wherein said adjusting step comprises the step of rotating said optical interference filter about an axis which is orthogonal to said reflected light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths of light which are transmitted.

48. The method of claim 44 wherein said adjusting step comprises the step of rotating said optical interference filter about an axis which is orthogonal to said incident light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths that are substantially prevented from transmitting through said optical interference filter.

49. The method of claim 44 wherein said adjusting step comprises the step of rotating said optical interference filter about an axis which is orthogonal to said reflected light propagation axis, wherein rotation of said optical interference filter selectably adjusts the distribution of wavelengths that are substantially prevented from transmitting through said optical interference filter.

50. The method of claim 39 wherein said step of passing light through a polarizer generates light having a p-polarization state propagating along said incident light propagation axis.

51. The method of claim 39 where said light propagating along said incident light propagation axis undergoes total internal reflection upon interaction with said optical assembly.

52. The method of claim 39 further comprising the step of collimating light from said polychromatic optical source.

53. The method claim 39 further comprising the step of focusing said light propagating along said reflected light propagation axis onto said detector.

54. The method of claim 39 wherein said light has wavelengths in the near infrared region of the electromagnetic spectrum.

55. The method of claim 39 wherein said optical assembly further comprises a flow cell operationally connected to said probe region for delivering chemical species into said probe region.

56. The method of claim 55 further comprising the step of flowing chemical species through said flow cell, thereby changing the composition of said probe region.

57. The method of claim 55 further comprising the step of flowing chemical species through said flow cell, thereby changing the refractive index of said probe region.

58. The method of claim 55 further comprising the step of flowing chemical species through said flow cell, thereby changing the thickness of said probe region.

59. The method of claim 55 wherein said flow cell is a microfluidic flow cell.

60. A method of generating an image of a probe region comprising the steps of:

passing light from a polychromatic light source through a polarizer, thereby generating light propagating along an incident light propagation axis;

directing said light onto an optical assembly, said optical assembly comprising a dielectric layer, a dielectric sample layer and a conducting layer positioned between said dielectric layer and said dielectric sample layer, thereby generating light propagating along a reflected light propagation axis, wherein a portion of said dielectric sample layer adjacent to said conducting layer comprises said probe region;

passing said light through a selectably adjustable wavelength selector positioned in the optical path between said light source and a detector;

detecting said light with said detector, thereby generating said image of said probe region, and

adjusting said selectably adjustable wavelength selector to transmit light having a distribution of wavelengths selected to generate surface plasmons on a surface of said conducting layer in contact with said dielectric sample layer.

61. The method of claim 60 wherein said detector is a charge coupled device.

62. A method of detecting a change in the refractive index of a probe region comprising the steps of:

passing light from a polychromatic light source through a polarizer, thereby generating light propagating along an incident light propagation axis;

directing said light onto an optical assembly, said optical assembly comprising a dielectric layer, a dielectric sample layer and a conducting layer positioned between said dielectric layer and said dielectric sample layer, thereby generating light propagating along a reflected light propagation axis, wherein a portion of said dielectric sample layer adjacent to said conducting layer comprises said probe region;

passing said light through a selectably adjustable wavelength selector positioned in the optical path between said light source and a detector, wherein said selectably adjustable wavelength selector is adjusted to transmit incident light having a distribution of wavelengths selected to generate surface plasmons on a surface of said conducting layer in contact with said dielectric sample layer;

detecting said light with said detector, thereby generating at least one reference measurement,

detecting said light with said detector, thereby generating at least one analytical measurement, and

comparing said reference measurement and said analytical measurement to detect said change in the refractive index of said probe region.

63. The method of claim 62 wherein said optical assembly further comprises a flow cell for introducing chemical species into said probe region.

64. The method of claim 63 further comprising the step of introducing chemical species into said probe region.