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© KONICA MINOLTA
Simulating Surface Plasmons at Metal Surfaces and its Application in Optoelectronic Devices with COMSOL Multiphysics
Leiming Wang, Senior Researcher
Konica Minolta Laboratory USA
© KONICA MINOLTA 1
Outline
Introduction
• Surface plasmon polaritons (SPP)
Simulation of SPP using COMSOL Wave Optics
• Prism coupling
• Scattering configuration (grating coupling)
• Explore SPP properties via scattering simulation
Application examples
• Plasmon energy loss in OLED
• Surface plasmon-enhanced fluorescence spectroscopy (SPFS)
© KONICA MINOLTA 2
Plasmonics: merging electronics and photonics at the nanoscale
© KONICA MINOLTA 3
Surface plasmon polaritons – a guided surface wave
Transverse magnetic (TM, or p-polarized) mode – Hz, Ex, Ey
“Phase-matching” (ΔK) condition for SPP excitation
K0sin(ө) Kspp
ΔK
Ag
475nm
© KONICA MINOLTA 4
SPP excitation – prism coupling
“Phase-matching” condition:
өn1
n0
Ɛm
өn1n0
Ɛm
sppkkn )sin(01
Kretschmann-Raether Otto
Yushanov, et al, COMSOL Conference 2012
© KONICA MINOLTA 5
SPP excitation – scattering
Symmetry breaking by discontinuity/defect provides a
broad spectrum of spatial frequency, allowing the phase
matching (Δk) to be attained for SPP excitation.
ө
(1) Full-field simulation w/o the slit to generate incident field for step 2 (ө = 30o).
(2) Scattered-field simulation with the output from step 1 as the incident field.
Scattering configuration enables the local excitation of SPP and opens the way for further study on its
wave properties such as attenuation, interference, focusing, etc.
© KONICA MINOLTA 6
SPP excitation – grating coupling
Finite grating is a special case of scattering configuration,
with resonance:
ө
p
sppkpmk )2()sin(0
Ө = 0o
Ө = 16.5o (resonance)
Ө = 30o
© KONICA MINOLTA 7
Coupled SPPs at thin metal film
SPPs at the two interfaces of thin metal film interact to form
two coupled SPP modes:• Anti-symmetric bound mode (ab): strong confinement, strong damping (short range SPP).
• Symmetric bound mode (sb): weak confinement, small damping (long range SPP).
ө+ - + -+ - + -
+ + + +- - - -
ab sb
|Ey|
|Ey|
ab
sb
Ө = 0o
Ө = 65o
© KONICA MINOLTA 8
Adiabatic focusing of SPP by thin wedge
The dispersion with respect to film thickness
leads to adiabatic focusing of the thin film
coupled SPP in a wedge structure.
ө
Wang, et al, PHYSICAL REVIEW B 86, 165408 (2012)
© KONICA MINOLTA 9
SPP focusing lens
Engineering the wave front of SPP by 2D
arrangement of local coupling structures.
k0
© KONICA MINOLTA 10
Konica Minolta OLED lighting
© KONICA MINOLTA 11
Plasmon energy loss in OLED
Typical power distribution spectrum of an
OLED viewed in the k-space*
*Reineke et al., Rev. Mod. Phys. 85, 1245–1293 (2013)
© KONICA MINOLTA 12
Reducing plasmon loss in OLED by nanostructured cathode
|E
z|
Pz @ 535 nm
“Let there be light: a brighter future for OLED”,
IEEE Spectrum, September 2016
Wang, et al, COMSOL Conference 2015
© KONICA MINOLTA 13
Surface plasmon-enhanced bio-sensing
© KONICA MINOLTA 14
Trade-off btw SP-enhanced excitation and –quenched emission in SPFS
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 20 40 60 80 100 120 140 160 180 200
SP
(%)
d (nm)
12
10
8
6
4
2
0
I/I 0
10008006004002000
y (nm)
FEM simulation exponential fitting
water
prism
50nm Au
Excitation field enhancement SP quenching of fluorescence emission
© KONICA MINOLTA 15