Download Energy Transfer and Plasmonics in Metal Tip Fluorescence and more Study notes Electrical and Electronics Engineering in PDF only on Docsity! Fluorescence Near Metal Tips The roles of energy transfer and surface plasmon polaritons Nader A. Issa and Reinhard Guckenberger Mark Knight Laboratory for Nanophotonics
RICE UNIVERSITY Model Geometry
(a)
Axis of rotational symmetry
wee PM eee
lum
AVA
Vertical | y Glass
electric |
Excitation & Detection • Uncommon • γdet ≈ ξ γr • Most common case • γdet = ξ γexc q – γexc : excitation rate – q : quantum efficiency Near Saturation N≈1 Far Below Saturation N<<1 For a single molecule: γdet = ξ N γr • ξ : detection efficiency of instruments • N : probability of finding molecule in excited state • γ : decay rate. γ = P / (h ν) Model Limitations • Excludes effects of non-locality • Ignores surface electron scattering – May underestimate nonradiative rates for distances between 0.5 - 10 nm – Mean free path of electrons is ~10 nm for infrared wavelengths RICE UNIVERSITY Model Geometry
(a)
&
a
—
&
a
o
5
= Medium:
6 - Air
=
3°
“ :
2 | 5
<
i 4 oo
: | Vertical
= sem io 4 electric
Tum ‘os dipole
Ave 3
Vertical | 4 Glass 4
electric |
dipole f
Fig. 1. (a) Example solution, Re(H,), with diagram overlay of the model geometry. This
cross-section view is symmetric about indicated axis of rotation. In this figure, the tip (silver)
is at a distance D=100nm from the dipole and 4 =550nm. The metal tip supports a propagating
SPP that is clearly visible. The power in propagating SPPs remaining at the top of the tip is
measured prior to the top PML, and is counted as nonradiative. (b) Example FEM meshing
near the tip showing adaptation and fine mesh near nano-scale features: D=10nm. (c) Diagram
illustrating different parts of the tip where the integrated resistive losses are attributed to SPP
losses (volume 1) and local energy transfer (volume 2).
Origin of LET Quenching • Distance scale: < 5 nm • Quantum view – near-field of molecule penetrates metal – excites excitons (electron-hole pairs) • Classical view – Lossy surface waves • Induced charge-density oscillations – Interpret as dipole-dipole energy transfer to volume of dipoles comprising metal RICE UNIVERSITY Movie
Cross-section of rotationally symmetric solution. Magnetic field: |Re(H)], D=986.08nm
RICE UNIVERSITY Quantum Efficiency
Silver tip
A= 550M, € pei = —12.9 + 0.437
1
08
0.6
0.4
0.2
D (nm)
ge YY Vg ¥ > Yen /Y
Fig. 5. Comparison of efficiencies for two different initial quantum efficiencies. The curves
are nearly identical for D < ~10nm (see text).
Nod to the Past • General effects were summed up in 1984 RICE UNIVERSITY
Playing with COMSOL
RICE UNIVERSITY Dipole above Nanoshell
lambda0_rfwh(1)=3e-7 Max: 5.00e-3
Surface: Magnetic field, phi component [A/m) x10?
x10? 5
4
4
3
3
2
2
1
0 1
-l
0
2
-1
3
-2
-4
4 3 2 -1 0 1 2 3 4 5 6 ? 8 3
x1o-? Min: ~3.00e~3
