Optical sensing based on surface plasmon resonances in nanostructures

1. An optical sensing device, comprising:

a nanohole array comprising a substrate and a metal layer formed on the substrate to include an array of holes arranged in a periodic two-dimensional pattern and to be in contact with a sample under measurement, each hole having a dimension less than one wavelength of probe light to which the nanohole array is responsive to produce surface plasmons at an interface of the metal layer and the sample under a surface plasmon resonance condition;

an input optical module to direct a collimated input optical probe beam at the wavelength of the probe light to the nanohole array, the input optical module comprising an optical polarization control unit operable to control an input optical polarization of the collimated input optical probe beam incident to the nanohole array; and

an output optical module to receive an optical output produced by the surface plasmons at the interface between the metal layer and the sample, the output optical module comprising an output optical polarizer to select light in the optical output at a selected output polarization for optical detection,

wherein the input optical module further comprises an actuator to control an incident angle of the collimated input optical probe beam to achieve the surface plasmon resonance condition.

2. The device as in claim 1 , wherein the optical polarization control unit and the output optical polarizer are configured to be orthogonal to each other in polarization to produce a Lorentzian spectral profile in the optical output that transmits through the output optical polarizer.

3. The device as in claim 1 , wherein the output optical module comprises:

an optical sensing device to receive and capture an image of the optical output that transmits through the output optical polarizer; and

an optical imaging unit placed in an optical path between the nanohole array and the optical sensing device to image the nanohole array onto the imaging device.

4. The device as in claim 3 , wherein the optical sensing device is a camera and the optical imaging unit comprises two lenses in a 4f lens configuration.

5. The device as in claim 1 , wherein the input optical module comprises a tunable light source to control at least one of the wavelength and the amplitude of the collimated input optical probe beam to achieve the surface plasmon resonance condition.

6. The device as in claim 1 , wherein the nanohole array comprises a microfluidic channel in contact with the metal film to support a fluid sample under measurement.

7. The device as in claim 6 , wherein the microfluidic channel is formed from a polymer.

8. The device as in claim 1 , wherein the nanohole array comprises a plurality of parallel microfluidic channels in contact with the metal film and each microfluidic channel supports a respective fluid sample under measurement.

9. The device as in claim 1 , wherein the optical output produced by the surface plasmons at the interface between the metal layer and the sample is an optical transmission through the metal film and the sample and,

wherein the input and output optical modules are located relative to the nanohole array to direct the collimated input optical probe beam to the nanohole array and to receive the optical output from the nanohole array, respectively, on opposite sides of the nanohole array.

10. The device as in claim 1 , wherein the optical output produced by the surface plasmons at the interface between the metal layer and the sample is an optical reflection by the metal film,

wherein the input and output optical modules are located relative to the nanohole array to direct the collimated input optical probe beam to the metal film of the nanohole array and to receive the optical output reflected from metal film of the nanohole array so as to direct the collimated input optical probe beam and receive the optical output on a same side of the nanohole array.

11. The device as in claim 1 , wherein each hole in the metal film of the nanohole array is spatially anisotropic in shape.

12. The device as in claim 11 , wherein each hole in the metal film of the nanohole array is elliptical.

13. The device as in claim 1 , wherein the metal film comprises at least one of Ag, Au, Al and Cu.

14. The device as in claim 1 , wherein the polarization control unit in the input optical module comprises first and second optical polarizers and a quarter wave plate between the first and second optical polarizers.

15. The device as in claim 1 , wherein the output optical modulator comprises a quarter wave plate or a liquid crystal modulator to filter the optical output that is received by the output optical polarizer.

16. The device as in claim 1 , wherein the metal film of the nanohole array is functionalized with a biomolecular recognition element.

17. The device as in claim 1 , wherein each hole in the nanohole array is a through hole in the metal film.

18. The device as in claim 1 , wherein each hole in the nanohole array penetrates a part of the metal film without penetrating through the metal film.

19. The device as in claim 1 , further comprising a mechanism to adjust a relative orientation between the input optical module and the nanohole array to adjust an incident angle of the collimated input optical probe beam at the nanohole array.

20. The device as in claim 1 , wherein the nanohole array further comprises different sample areas in contact with different samples under illumination by the collimated input optical probe beam; and

wherein the input optical module is configured to produce different collimated optical probe beams to simultaneously illuminate the different sample areas.

21. The device as in claim 20 , wherein the different sample areas are respectively functionalized with different biomolecular recognition elements on the metal film.

22. An optical sensing method, comprising:

providing a nanohole array comprising a metal layer and an array of holes arranged in a periodic two-dimensional pattern to be in contact with a sample under measurement, wherein each hole has a dimension less than one wavelength of probe light to which the nanohole array is responsive to produce surface plasmons at an interface of the metal layer and the sample under a surface plasmon resonance condition;

directing a collimated input optical probe beam at the wavelength of the probe light to the nanohole array under the surface plasmon resonance condition to excite surface plasmons at the interface of the metal layer and the sample;

directing light in an optical output produced by the surface plasmons at the interface between the metal layer and the sample in a selected output polarization into a camera;

processing an image captured by the camera to extract information of the sample; and

controlling an incident angle of the collimated input optical probe beam to achieve the surface plasmon resonance condition.

23. The method as in claim 22 , further comprising:

controlling input polarization of the collimated input optical probe beam and the selected output polarization for the light captured by the camera to be orthogonal to each other to produce a Lorentzian spectral profile in the light captured by the camera.

24. The method as in claim 22 , further comprising:

controlling at least one of the wavelength and the amplitude of the collimated input optical probe beam to achieve the surface plasmon resonance condition at the interface between the metal layer and the sample.

25. The method as in claim 22 , further comprising:

functionalizing the metal layer with a biomolecular recognition element to target selected samples particles for measurement.

26. The method as in claim 25 , further comprising:

applying a molecular fluorescent tag in the sample to enhance the measurement specificity.

27. The method as in claim 22 , further comprising:

functionalizing different sample areas in the metal layer with different biomolecular recognition elements, respectively, to target different selected samples particles for measurement.

28. The method as in claim 27 , further comprising:

controlling the collimated input optical probe beam to produce different collimated optical probe beams to simultaneously illuminate a plurality of the different sample areas to simultaneously measure different samples attached to the different sample areas.

29. The method as in claim 22 , further comprising:

attaching at least one microfluidic channel to the metal film to supply a liquid sample to be measured by the collimated input optical probe beam.

30. The method as in claim 22 , further comprising:

using the collimated input optical probe beam to produce different collimated optical probe beams to simultaneously illuminate different sample areas on the nanohole array to simultaneously measure the different sample areas.

31. An optical sensing device, comprising:

a nanohole array comprising a metal layer with a two-dimensional array of holes configured to interface with a sample under measurement and to support surface plasmon under excitation of probe light, each hole having a dimension less than one wavelength of the probe light;

an input polarization control unit to control input polarization of an input optical probe beam of the probe light incident to the nanohole array;

an output optical polarizer to receive signal light which is transmission of the input optical probe beam through the nanohole array and the sample to select a polarization of the signal light for optical detection,

wherein the input polarization control unit and the output optical polarizer are configured to be orthogonal to each other in polarization; and

a positioning stage to hold the nanohole array and to adjust the orientation of the nanohole array relative to the input optical probe beam to achieve a surface plasmon resonance condition at an interface between the metal layer and the sample.

32. The device as in claim 31 , wherein the nanohole array comprises a microfluidic channel in contact with the metal film to support a fluid sample under measurement.

33. The device as in claim 31 , wherein the nanohole array comprises a plurality of parallel microfluidic channels in contact with the metal film and each microfluidic channel supports a respective fluid sample under measurement.

34. The device as in claim 31 , wherein each hole in the metal film of the nanohole array is spatially anisotropic in shape.

35. The device as in claim 31 , wherein the metal film of the nanohole array is functionalized with a biomolecular recognition element.

36. The device as in claim 31 , wherein the nanohole array further comprises different sample areas in contact with different samples under illumination by the collimated input optical probe beam; and

the device further comprises an input optical module to produce different collimated optical probe beams to simultaneously illuminate the different sample areas.

37. The device as in claim 36 , wherein the different sample areas are respectively functionalized with different biomolecular recognition elements on the metal film.

38. The optical sensing device as in claim 31 , comprising a tunable light source to control at least one of the wavelength and the amplitude of the input optical probe beam to achieve the surface plasmon resonance condition.

39. An optical sensing device, comprising:

a substrate;

a metal layer formed on the substrate and patterned to comprise a two-dimensional array of holes configured to interface with a sample under measurement and to support surface plasmons under excitation of probe light, each hole having a dimension less than one wavelength of the probe light;

a plurality of microfluidic channels formed in contact with the metal film, wherein each microfluidic channel supports a respective fluid sample under measurement; and

an input optical module to direct a collimated input optical probe beam at the wavelength of the probe light to the nanohole array, the input optical module comprising

an optical polarization control unit operable to control an input optical polarization of the collimated input optical probe beam incident to the nanohole array, and

an actuator to control an incident angle of the collimated input optical probe beam to achieve a surface plasmon resonance condition at an interface between the metal layer and the sample.

40. The device as in claim 39 , further comprising:

an output optical module to receive an optical output produced by the surface plasmons at the interface between the metal layer and the sample, the output optical module comprising an output optical polarizer to select light in the optical output at a selected output polarization for optical detection; and

a camera positioned to capture an image of the selected light that transmits through the output optical polarizer.

41. The device as in claim 40 , wherein the optical polarization control unit and the output optical polarizer are configured to produce a Lorentzian spectral profile in the optical output that transmits through the output optical polarizer.

42. The device as in claim 39 , wherein each hole in the metal film of the nanohole array is spatially anisotropic in shape.

43. The device as in claim 39 , wherein the metal film of the nanohole array is functionalized with a biomolecular recognition element.

44. The device as in claim 39 , wherein the nanohole array further comprises different sample areas in contact with different samples; and

wherein the input optical module is configured to produce different collimated optical probe beams to simultaneously illuminate the different sample areas.

45. The device as in claim 44 , wherein the different sample areas are respectively functionalized with different biomolecular recognition elements on the metal film.

46. The device as in claim 39 , wherein the input optical module comprises a tunable light source to control at least one of the wavelength and the amplitude of the collimated input optical probe beam to achieve the surface plasmon resonance condition.