Surface plasmon resonance apparatus and method

• US 6,667,807 B2
• Filed: 03/30/2001
• Issued: 12/23/2003
• Est. Priority Date: 03/30/2001
• Status: Expired due to Fees

• Current Assignee: Optech Ventures, LLC
• Original Assignee: Optech Ventures, LLC
• Inventors: Lieberman, Robert A.
• Primary Examiner(s): STAFIRA, MICHAEL PATRICK
• Application Number:
  US09/823,858
• Publication Number:
  US 20020140937A1
• Time in Patent Office: 998 Days
• Field of Search: 356/445, 356/136
• US Class Current: 356/445
• CPC Class Codes: G01N 21/553 and using surface plasmons fluorescence excitation G01N21/648; enhanced Raman G01N21/658

Abstract

A surface plasmon resonance device includes a metal thin film, a dielectric thin film on an optical member and, in addition, an electro-optically active thin film either between the metal thin film and the dielectric thin film or between the optical member and the metal thin film. The electro-optically active thin film is subject to a voltage which is varied to tune the resonance condition of the device.

Claims

1. Apparatus comprising an optical structure having a planar surface and means for directing polarized light through said optical structure at said surface at an angle to obtain total internal reflection from said surface, said apparatus comprising a metallic layer and a recognition layer on said surface, said apparatus also including a voltage responsive layer for changing the refractive index thereof in a manner to vary the penetration of said light into said recognition layer, including a voltage source connected to said voltage responsive layer and including control means for varying the voltage impressed across said voltage responsive layer in a manner to modulate the refractive index of said voltage responsive layer about a set point.

2. Apparatus as in claim 1 wherein said set point is a null point.

3. Apparatus as in claim 1 including a feedback loop responsive to a minimum light intensity signal for changing the voltage impressed upon said voltage responsive layer to maintain a minimum light intensity condition.

4. Apparatus as in claim 2 also including output means for detecting the light intensity signal reflected from said surface.

5. A method for the modulation of plasmon resonance in a surface Plasmon resonance device including a total internal reflection element, a thin metallic layer and a recognition layer, said method comprising the steps of forming adjacent to said metallic layer, an electro-optically active layer and impressing across said electro-optically active layer a voltage signal for varying the index of refraction thereof about a set point.

6. A method as in claim 5 wherein said voltage is varied about a null point.

7. A method as in claim 5 wherein said voltage is varied in a manner to maintain a reflected light signal at a minimum intensity.

8. Apparatus comprising an optical structure having a planar surface and means for directing polarized light through said optical structure at said surface at an angle to obtain total internal reflection from said surface, said apparatus comprising a metallic layer and a recognition layer on said surface, said apparatus also including a voltage responsive layer for changing the refractive index thereof in a manner to vary the penetration of said light into said recognition layer, said recognition layer comprising a dielectric film and said voltage layer is located between said metallic layer and said dielectric film.

9. Apparatus comprising an optical structure having a planar surface and means for directing polarized light through said optical structure at said surface at an angle to obtain total internal reflection from said surface, said apparatus comprising a metallic layer and a recognition layer on said surface, said apparatus also including a voltage responsive layer for changing the refractive index thereof in a manner to vary the penetration of said light into said recognition layer, said voltage responsive layer comprising an electro-optically active thin film of a material selected from the class consisting of Polyamide, Polyanaline, Poly (N-benzyl aniline), Poly (2-ethoxyanaline), Poly (diarylaniline) and Poly (DRI-MMA).

10. Apparatus comprising an optical structure having a planar surface and means for directing polarized light through said optical structure at said surface at an angle to obtain total internal reflection from said surface, said apparatus comprising a metallic layer and a recognition layer on said surface, said apparatus also including a voltage responsive layer for changing the refractive index thereof in a manner to vary the penetration of said light into said recognition layer, said voltage responsive layer comprising an electro-optically active thin film of a material comprising Poly (DRI-MMA).

11. A method for determining the change in thickness of a specimen over time using a surface plasmon resonance device including a total internal reflection element, a thin metallic layer and a recognition layer containing the specimen, said method comprising the steps of,

forming adjacent to the metallic layer an electro-optically active layer;

impressing across the electro-optically active layer a voltage for varying the index of refraction of the electro-optically active layer;

setting the voltage to a first null point at which there is a minimum of reflectivity of the surface plasmon resonance device to establish a voltage level for the first null point;

at a later time upon a change in the reflectivity of the first null point indicating a change in the index of refraction of the specimen, changing the impressed voltage to establish a new null point of minimum reflectivity whereby the change in the impressed voltage to return to a null point is a direct measure of the change in refractive index of the specimen; and

comparing the impressed voltage of the first null point to the impressed voltage of the new null point and processing the comparison to determine the thickness change of the specimen.

12. The method of claim 11 further comprising controlling the electro-optically active layer to detect minimum light by use of a DC voltage and adding a small modulation voltage, oscillating at a selected frequency, f, and providing a frequency detector for detecting change in the signal as 2 f.

13. The method of claim 11 further comprising using the signal as a feedback loop to maximize the 2 f signal whereby very fast automatic locking at the minimum light condition will result and the voltage necessary to achieve the locking will be a direct measurement of the change in thickness of the specimen.

14. The method of claim 11 further comprising using sequential measurements over time determining the rate of change of thickness of the specimen.