Dielectric. Z. Evanescent Field. Surface Plasmon. Metal. ≈ 50nm. Prism. θ i. θ r. θ i = θ sp. θ i = θ r θ i > θ c. Surface plasmon resonance sensing.
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θi = θsp
θi = θr
Surface plasmon waves extend few hundred nanometres above the metal film. They are affected by the refractive index in this region.
Surface plasmon resonance sensors are important for ultrasensitive immunoassays
with applications in health diagnostics
Conventional sensor system
surface plasmon at
interface, wavevector k||
dj = zj – zj-1
Source: S. Orfanidis, “Electromagnetic waves and antennas” pp.81-108
R.U.S. Kurosawa et al, PRB 33,789 (1986)
Surface Plasmon Resonance Sensing System
front edge of reflectance curve
Nanostructures increase device sensitivity
Develop a new optical based sensor technology for rapid detection of trace pathogens and chemicals in the environment.
Apply surface nano-patterning techniques to a Surface Plasmon Resonance (SPR) sensing system to achieve unprecedented sensitivity levels
Surface plasmons are electromagnetic waves excited by light in metal films.
Surface plasmons sense the analyte
Examples of nanostructures
Rigorous coupled wave analysis for modelling nano-modified surface plasmon based sensing systems
Reflectance results showing the effect of variation of
nanowire period Λ. Insert: Diagram of setup under consideration.
Reflectance results showing the effect of variation of nanowire width and height (W, H).
Insert: Diagram of setup under consideration.
These simulations were carried out using DiffractMOD, an RCWA based software package from RSoft
Layer ~ 200 nm
Surface Plasmon Coupled Emission
Excitation scheme adapted for microscopy
Two photon SPCE demonstrated
Schematic diagram of a model bioassay
Feasibility of bioassays in dense media