Self-referencing waveguide grating sensors

• US 7,203,386 B2
• Filed: 09/21/2004
• Issued: 04/10/2007
• Est. Priority Date: 09/21/2004
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Krol, Mark F., Salik, Mark D.
• Primary Examiner(s): Font; Frank G.
• Assistant Examiner(s): Mooney; Michael P.
• Application Number:
  US10/947,021
• Publication Number:
  US 20060062509A1
• Time in Patent Office: 931 Days
• Field of Search: 385/12, 385/37, 385/129, 356/246, 422/58, 422/68.1, 422/102, 422/82.11, 435/7.1
• US Class Current: 385/12
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01N 21/7743 the reagent-coated grating coupling light in or out of the waveguide
• CPC Class Codes: G01N 33/54373 involving physiochemical end-point determination, e.g. wave-guides, FETS, gratings

Abstract

Self-referencing optical sensors and methods are described herein that can be used to detect bio-chemical interactions (e.g., biological binding of antigen-antibody pairs) that occur in for example a microplate. In one embodiment, the self-referencing optical sensor includes a substrate, a lower (reference) waveguide grating structure, a buffer layer and an upper (sensing) waveguide grating structure. This self-referencing optical sensor enables an optical interrogation system to detect a bio-chemical interaction independent of the effect of temperature by measuring a reference signal associated with the lower (reference) waveguide grating structure and measuring a sensing signal associated with the upper (sensing) waveguide grating structure. These two signals are then subtracted from one another to determine a sensing measurement that represents whether or not the bio-chemical interaction occurred that is independent of the effect of temperature. This is all possible because the self-referencing optical sensor has a lower (reference) waveguide grating structure with a thickness that was sized to make a rate of change of a lower resonant wavelength/temperature variation (Δλ^L/ΔT) substantially equal to a rate of change of an upper resonant wavelength/temperature variation (Δλ^U/ΔT). Several other embodiments of self-referencing optical sensors which have a specific structures and/or a specific compositions are also described herein.

Claims

1. An athermal self-referencing optical sensor comprising:

a substrate;

a lower waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure, wherein said lower waveguide grating structure has a thickness that was sized to make a rate of change of a lower resonant wavelength/temperature variation (Δ

λ

^L/Δ

T) of said lower waveguide grating structure substantially equal to a rate of change of an upper resonant wavelength/temperature variation (Δ

λ

^U/Δ

T) of said upper waveguide grating structure.

2. The optical sensor of claim 1, wherein when said optical sensor is interrogated then a reference signal and a sensing signal can be measured and subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not a bio-chemical interaction took place in a sensing region of said upper waveguide grating structure.

3. The optical sensor of claim 1, wherein said Δ

λ

^L/Δ

T and Δ

λ

^U/Δ

T are represented by;

4. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate;

a lower waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure, wherein said lower waveguide grating structure has a thickness that was sized to make a rate of change of a lower resonant wavelength/temperature variation (Δ

λ

^L/Δ

T) of said lower waveguide grating structure substantially equal to a rate of change of an upper resonant wavelength/temperature variation (Δ

λ

^U/Δ

T) of said upper waveguide grating structure;

receiving an output optical beam from said optical sensor; and

analyzing the output optical beam to determine a reference signal and a sensing signal which are then subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not the bio-chemical interaction took place in the sensing region of said optical sensor.

5. The method of claim 4, wherein said Δ

λ

^L/Δ

T and Δ

λ

^U/Δ

T are represented by;

6. An athermal self-referencing optical sensor comprising:

a substrate;

an anti-resonant reflecting optical waveguide (ARROW) grating structure;

a buffer layer; and

an upper waveguide grating structure.

7. The optical sensor of claim 6, wherein:

said ARROW grating structure has a waveguide mode that operates in TE polarization; and

said upper waveguide grating structure has a waveguide mode that operates in TM polarization.

8. The optical sensor of claim 6, wherein said ARROW grating structure has a grating depth that is larger than a grating depth of said upper waveguide grating structure.

9. The optical sensor of claim 6, wherein when said optical sensor is interrogated then a reference signal and a sensing signal can be measured and subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not a bio-chemical interaction took place in a sensing region of said upper waveguide grating structure.

10. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate;

an anti-resonant reflecting optical waveguide (ARROW) grating structure;

a buffer layer; and

an upper waveguide grating structure;

receiving an output optical beam from said optical sensor; and

analyzing the output optical beam to determine a reference signal and a sensing signal which are then subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not the bio-chemical interaction took place in a sensing region of said optical sensor.

11. The method of claim 10, wherein:

said ARROW grating structure has a waveguide mode that operates in TE polarization; and

said upper waveguide grating structure has a waveguide mode that operates in TM polarization.

12. The method of claim 10, wherein said ARROW grating structure has a grating depth that is larger than a grating depth of said upper waveguide grating structure.

13. An athermal self-referencing optical sensor comprising:

a substrate;

a Bragg waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure.

14. The optical sensor of claim 13, wherein said substrate, Bragg waveguide grating structure, said buffer layer and said upper waveguide grating structure have predetermined refractive indices and thicknesses which ensure that during an interrogation process a wavelength shift with temperature is substantially equal for both a sensor signal and a reference signal.

15. The optical sensor of claim 13, wherein when said optical sensor is interrogated then a surface binding effect can be separated from a temperature change by solving a pair of linear equations:

λ

_S=C_S·

Δ

t_bio+K_S·

Δ

T

λ

_R=C_R·

Δ

t_bio+K_R·

Δ

T

where;

16. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate;

a Bragg waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure;

receiving an output optical beam from said optical sensor; and

analyzing the output optical beam to determine a reference signal and a sensing signal which are then subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not the bio-chemical interaction took place in the sensing region of said optical sensor.

17. The method of claim 16, wherein said substrate, Bragg waveguide grating structure, said buffer layer and said upper waveguide grating structure have predetermined refractive indices and thicknesses which ensure that during an interrogation process a wavelength shift with temperature is substantially equal for both a sensor signal and a reference signal.

18. The method of claim 16, wherein when said optical sensor is analyzed then a surface binding effect can be separated from a temperature change by solving a pair of linear equations:

λ

_S=C_S·

Δ

t_bio+K_S·

Δ

T

λ

_R=C_R·

Δ

t_bio+K_R·

Δ

T

where;

19. An optical sensor comprising:

a substrate; and

a waveguide grating structure, wherein when said waveguide grating structure is interrogated then one can use higher mode properties of said waveguide grating structure to separate effects of a surface binding thickness (Δ

t_bio) from changes in a buffer solution refractive index (Δ

n_analyte).

20. The optical sensor of claim 19, wherein when said optical sensor is interrogated then one can separate the effects of the surface binding thickness (Δ

t_bio) from the changes in the buffer solution refractive index (Δ

n_analyte) by solving a pair of linear equations;

Δ

n_eff^m=0=B₀·

Δ

n_analyte+S₀·

Δ

t_bio

Δ

n_eff^m=1=B₁·

Δ

n_analyte+S₁·

Δ

t_bio

where;

B₀, S₀, B₁, S₁ are the bulk and surface optical field sensitivities (OFSs) for two different modes; and

Δ

n_{eff for m=0 and m=1} are the effective indexes of waveguide mode propagations for the waveguide grating structure.

21. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate; and

a waveguide grating structure;

receiving an output optical beam from said optical sensor; and

analyzing said received optical beam and using higher mode properties of said waveguide grating structure to separate effects of a surface binding thickness (Δ

t_bio) from changes in a buffer solution refractive index (Δ

n_anaylyte) to determine whether or not the bio-chemical interaction took place in the sensing region of said optical sensor.

22. The method of claim 21, wherein when said optical sensor is analyzed then one can separate the effects of the surface binding thickness (Δ

t_bio) from the changes in the buffer solution refractive index (Δ

n_analyte) by solving a pair of linear equations;

Δ

n_eff^m=0=B₀·

Δ

n_analyte+S₀·

Δ

t_bio

Δ

n_eff^m=1=B₁·

Δ

n_analyte+S₁·

Δ

t_bio

where;

B₀, S₀, B₁, S₁ are the bulk and surface optical field sensitivities (OFSs) for two different modes; and

Δ

n_{eff for m=0 and m=1} are the effective indexes of waveguide mode propagations for the waveguide grating structure.

23. An optical sensor comprising:

a substrate;

a reference waveguide grating structure;

a barrier layer; and

a sensing waveguide grating structure, wherein a thickness and a refractive index of said barrier layer were determined so there is a high isolation for a quasi-guided mode of said reference waveguide grating structure and so that the quasi-guided mode is biased towards a sensing region of said sensing waveguide grating structure.

24. The optical sensor of claim 23, wherein when said optical sensor is interrogated then a reference signal and a sensing signal can be measured and subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not a bio-chemical interaction took place in the sensing region of said sensing waveguide grating structure.

25. The optical sensor of claim 23, wherein:

said substrate is made from cyclo olefin;

said reference waveguide grating structure is made from Ta₂O₅;

said barrier layer is made from SiO₂; and

said sensing waveguide grating structure is made from Ta₂O₅.

26. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate;

a reference waveguide grating structure;

a barrier layer; and

a sensing waveguide grating structure, wherein a thickness and a refractive index of said barrier layer were determined so there is a high isolation for a quasi-guided mode of said reference waveguide grating structure and so that the quasi-guided mode is biased towards a sensing region of said sensing waveguide grating structure;

receiving an output optical beam from said optical sensor; and

analyzing the output optical beam to determine a reference signal and a sensing signal which are then subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not the bio-chemical interaction took place in the sensing region of said optical sensor.

27. The method of claim 26, wherein:

said substrate is made from cyclo olefin;

said reference waveguide grating structure is made from Ta₂O₅;

said barrier layer is made from SiO₂; and

said sensing waveguide grating structure is made from Ta₂O₅.

28. The optical sensor comprising:

a substrate;

a lower waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure, wherein said lower waveguide grating structure has a waveguide mode that is operated in TM polarization and said upper waveguide grating structure has a waveguide mode that is operated in TE polarization.

29. The optical sensor of claim 28, wherein said lower waveguide grating structure has a grating depth that is larger than a grating depth of said upper waveguide grating structure.

30. The optical sensor of claim 28, wherein when said optical sensor is interrogated then a reference signal and a sensing signal can be measured and subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not a biochemical interaction took place in a sensing region of said upper waveguide grating structure.

31. A method for detecting a bio-chemical interaction in a sensing region of an optical sensor, said method comprising the steps of:

directing a light beam at the optical sensor which includes;

a substrate;

a lower waveguide grating structure;

a buffer layer; and

an upper waveguide grating structure, wherein said lower waveguide grating structure has a waveguide mode that is operated in TM polarization and said upper waveguide grating structure has a waveguide mode that is operated in TE polarization;

receiving an output optical beam from said optical sensor; and

analyzing the output optical beam to determine a reference signal and a sensing signal which are then subtracted from one another to determine a self-referenced sensing measurement which indicates whether or not the bio-chemical interaction took place in a sensing region of said optical sensor.

32. The method of claim 31, wherein said lower waveguide grating structure has a grating depth that is larger than a grating depth of said upper waveguide grating structure.