1. Biometric Sensing: Plasmonic Theory and Label-free Applications
University of Minnesota-Duluth
EE4611: Semiconductor Physics and Devices
Joshua MacVey
Dr. S. Burns

2. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative
– Surface plasmon resonance biosensors: Quantitative

3. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative
– Surface plasmon resonance biosensors: Quantitative

4. The Why & What of biosensors
measure biomolecules:
Proteins
DNA
Etc.
applications in:
Diagnostics
Drug research
And, of course… $$

5. Strong Growth Predicted for Biosensors Market

6. Broad Categories: Labeled vs label-free
Extreme Generality

7. What is labeling?
Attachment of a fluorescent marker to biomolecule + =
measure signal under laser excitation
CAN WE THINK OF ANY PROS AND CONS TO LABELING?
signal
laser

8. Label-free sensing 1.55 μm Example: Ring-resonator ΔP Δλ Δλ
1.55 μm
Sun, et. al (2010)

10. Plasmonic Nanophotonics: a logical next step?

11. Why plasmonics?

12. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative & Theoretical
– Surface plasmon resonance biosensors: Quantitative

13. What is a plasmon?
A plasmon is a density wave in an electron gas - a collective oscillations of the free electron gas density. It is analogous to a sound wave, which is a density wave in a real gas of molecules.
Prof. Polman’s nanophotonic

14. What is a plasmon? + + + Bulk plasmon - - - k + - + Surface plasmon
+ + +
Ne2
Bulk plasmon
Plasmons in the bulk oscillate at
 p 
drude
m0
determined by the free electron density and effective mass
- - - k
+ - +
Plasmons confined to surfaces that can interact with light to form propagating “surface plasmon polaritons (SPP)”
Metal
Surface plasmon
Confinement effects result in resonant SPP modes in nanoparticles
Localized Surface plasmon
Prof. Polman’s nanophotonic

15. Surface plasmon (or surface plasmon-polariton )H
dielectric k E
+ - +
Note: this is a TM wave

16. Localized Surface plasmon

17. Wavelength dependent local field intensity

18. Plasmon propagation in micro-/nano- wires
R. M. Dickson et al. J. Phys. Chem. B 104, 6095 (2000)
B. Wild et al. ACS Nano 6, 472 (2011)

19. Applications of surface plasmons: An example device
Surface plasmon resonance biosensors
But before we get to this…

20. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative
– Surface plasmon resonance biosensors: Quantitative

21. Approaches to enhance biosensing performance
1. Enhancing sensitivity Δλ Δλ
Intensity
Intensity
Wavelength
low sensitivity
Wavelength
high sensitivity

22. Approaches to enhance biosensing performance
2. Enhancing selectivity
high Q-factor (high selectivity) P λ Δλ
Intensity P
FWHM λ
Sensitivity
Increases with increasing Q factor of the ring
Q  resonance/ Δλ
Wavelength
3dB
low Q-factor (low selectivity)

23. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative
– Surface plasmon resonance biosensors: Quantitative

24. Theory: Surface Plasmons
Evanescent TM polarized electromagnetic waves bound to the surface
of a metal
Benefits for Biosensing
High fields near the interface are very sensitive to refractive index changes
Gold is very suitable for biochemistry
Prism
Gold
From source
To detector R 
Dr. Peter Debackere’s Internal tutorial

25. Configurations: How can we excite SPP Modes?
Kretschman
Resonant Mirror
Otto Configuration
Configuration
Configuration
Fiber optics Sensors
Waveguide
Integrated SPR
LSPR nanosensor

26. Outline Biosensors: Introduction & Plasmonic Motivation
Some Needed Background: What is a plasmon?
Optical Biosensors
Label-Free Biosensor: Surface Plasmon Biosensors
– Surface plasmon resonance biosensors: Qualitative
– Surface plasmon resonance biosensors: Quantitative

27. Applications of surface plasmons: An example device
Surface plasmon resonance biosensors
And we’re back.

28. Kretschmann : Design Thickness of the Metal ?
Which metal ?

29. Response Curves Angular Response Spectral Response
Au thickness 44 nm, resonance angle degrees, resonant wavelength 650 nm

30. Response Curves Angular Response Spectral Response 657 nm 677 nm
65.61˚
65.71˚
Au thickness 44 nm, resonance angle degrees, resonant wavelength 650 nm

31. Response Curves Angular Response Spectral Response 1610 nm 1683 nm
22.73˚
22.75˚
Au-layer thickness 38 nm resonance angle degrees resonance wavelength 1600

32. Sensitivity BK 7 Glass Prism Silicon Prism Sensitivity [nm/RIU]
Wavelength shift [nm/RIU]
[nm/RIU]
spectral half width
300
250
200
150
100 50
Wavelength shift
Sensitivity total contribution
FRESN
10000
Wavelength [um]
Sensitivity [nm/RIU]
40000
90000
spectral half width
440
420
400
380
360
340
35000
85000
80000
30000
1.53
1.58
1.63
1.68
75000
25000
70000
20000
65000
15000
Sensitivity total contribution
60000
1.5
Wavelength [um]
1.65

33. LSPR biosensor consists of 3 major components
Localized surface plasmon resonance (LSPR) biosensor
LSPR sensing streptavidin binding to biotin
LSPR biosensor consists of 3 major components
Plasmonic surface:
signal transduction
Passivating layer: reduces nonspecific binding
Probe layer: recognize specific targets

34. Surface plasmon resonance (SPR) biosensor
SPR sensing streptavidin binding to biotin Ag
Δλ=12.7nm
Single nanoparticle SPR biosensor

35. Summary and Conclusions
- Electronics and Photonics alone are insufficient technologies given the need for enhanced speed and precision of biosensing devices.
- SPR technology is label-free and precise.
- SPR (Surface Plasmon Resonance) biosensing can be designed using a variety of geometric and chemical specifications reflective of chemical compositions.
- SPR technology may be further optimized for sensitivity and selectivity for specified wavelengths.
- SPR technology can further optimize spatial organization on chips.

36. References & Acknowledgements
B. Wild et al. ACS Nano 6, 472 (2011).
Bogaerts, W., Baets, R., & Bienstein, P. (2005, January). Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology. Journal of Lightwave Technology, 23(1),
How does surface plasmon resonance work?. (2015). In Bionavis. Retrieved April 15, 2015, from
Gaponenko, S. V. (2010). Introduction to nanophotonics (pp ). Cambridge: Cambridge University.
Khai Q. Le and P. Bienstman, Nanoplasmonic resonator for biosensing applications, 15th Annual Symposium of the IEEE Photonics Benelux Chapter, Deft, Netherlands (2010).
Khai Q. Le, B. Maes and P. Bienstman, Numerical study of plasmonic nanoparticles enhanced light emission in silicon light-emitting-diodes, 15th European Conference on Integrated Optics, United Kingdom (2010).
Sensor technology alert. distributed fiber sensor; surface plasmon resonance; wearable glucose sensor. (2006, December 1). In Frost & Sullivan.
Sun, Y., & Fan, X. (2010, June 6). Optical ring resonators for biochemical and chemical sensing. Anal. Bioanal Chemistry, doi: /s z
Powell, C. J., & Swan, J. B. (1959, March 30). Origin of the characteristic electron energy losses in aluminum. Physical Review Letters, doi:
R. M. Dickson et al. J. Phys. Chem. B 104, 6095 (2000).
For additional insight into the formal Mathematics and Physics behind SPR, see nanoplasmonic-related articles by:
Dr. P. Bienstman, Ghent University
Dr. Polman, Amolf University
Dr. Shalaev, Purdue University
Dr. Peter Debackere, UC-Berkeley

37. Key Concepts
1. Why should we focus on plasmonic biosensing? Explain using proportionality analysis of electronics and photonics alone.
2. What is a plasmon?
3. Decribe, qualitatively, the electromagnetics behind surface plasmon resonance.
4. What two things make for a good biosensor?
5.How does a SPR Kretschmann-designed biosensor work?