Q-Han Park Korea Univ.
description
Transcript of Q-Han Park Korea Univ.
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Q-Han Park
Korea Univ.
APSE 2010
1
The 4th Yamada Symposium on Advanced Photons and Science Evolution 2010
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EM field enhancement - antennas
Marconi's antenna system at Poldhu Cornwall, December
1901.
Monopole antenna
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Antenna - receiver
Frequency independent antenna
Yagi antenna
Horn antenna
at Bell Labs, Holmdel, NJ that Penzias and Wilson used to discover the 3 K
cosmic microwave background radiation in 1965.
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Nano-optical antenna
Radio/microwave
20 C.
Optical antenna
21 C.
1900 1945 21st century
mm
nm
Radar
MarconiRF antanna
: human to human
Opt. Ant.
New frontier: human to nanoworld
NanoopticsSERSCancerLEDSolar cell
:
Cell Phonem
4
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Optical antenna-monopole
Optical monopole antenna
Bring it down to the optical regime !
N.F. van Hulst group,
Nano Lett. 7,28, 2006
nature photonics, 2008
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Optical antenna - sensor
Optical monopole antenna Single molecule fluorescence
Excitation 514 nm
Fluorescence 570 nm
Emission control by a monopole antenna
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Optical antenna as a vector field probe
D.S.Kim, Q.Park. et al, Nature Photonics 1, 53 (2007)
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• dipole plasmon resonance Transmission, bio-sensing, cancer therapy
N. Halas group
S.Cho, Q.H.Park, Angew. Chem.Int. 2007
•128 nm core diameter, 14 nm gold shell,
• peak absorbance at 820 nm
• 10 degree Temp increase
Nano metal particles
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B.Kim, Q.H.Park, JACS, 2007; JACS 2009
J.Joo, Q.H.Park, Adv. Mater. 2007
SP enhanced PLSERS, silver nanorod+plate
S.W.Han, Q.H.Park, JACS. 2009
Dodecahedron
Metallic nano structures
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Optical antenna - bowtie
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Bow tie antenna – EUV generation
S.W.Kim et al, Nature 2008
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Bow tie antenna
S.W.Kim et al, Nature 2008
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Terahertz – nano
Terahertz field enhancement by a metallic nano slitoperating beyond the skin-depth limit D.S.Kim, Q.Park et al.
Nature Photonics 3, 152, 2009
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EM field enhancement by nano slit
Electric field enhancement: ~1,000 with λ /10,000 size gap
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Diffraction theory claculation
Mordal expansion
/2 /20
0
0
00
/20
0
,
2, cos
,
z z
m m
z
I ikx ik z h ikx ik z hy
II i z i zy m m
m
III ikx ik z hy
H x z dk k e k e
m xH x z A e B e
a
H x z dk k e
22 2 20 0, 2 /z mk k k k m a
0 2 /k
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2 20 0 0
0
2 20 0
0
22 2
02 2
m m
m m
h hi i
m m mn mn m m m mn mn m nm
h hi i
m m mn mn m m m mn mn mm
a aA e W B e W a
a aA e W B e W
Boundary matching
Mode Coupling Strength W:
2 20 00
(1)0 00 0
1 2 2cos cos
2
1 2 2cos cos
2
ik x ya a
mn
a a
m x n y eW dx dy dk
a a k k
m x n ydx dy H k x y
a a
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Mordal method vs. FDTD numerical method
width = 0.0002 thickness = 0.002
Good quantitative predictions, but only good for global/specific geometry
Ex field at x=a/2, z=h/2
Field enhancement
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Local capacitor model
-zone
Local Capacitor Model for Plasmonic Electric Field EnhancementQ.Park Phys. Rev. Lett.102, 093906, 2009
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Slit
-zone capacitance
Static capacitance restricted to the -zone
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02 vC
,
2
aE t kz t
E k
sint w
0 0
0
1
2
effInd SZ ZQ dA K ndl
iw
iw i
##############
2IndEiav
Conformal mapping
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2IndEiav
width = 0.00067 thickness = 0.002
Enhanced electric field inside the gap
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Real metal case
Good qualitative agreement
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x
y
zy-polarized incident light
Metal tip near metal surface
Intensity profile near metal tip (FDTD calculation:xy-cut)
xz-cut
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Bowtie
Spheroidal prolate coordinates Field enhancement
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sinh sin cos ,
sinh sin sin ,
cosh cos
x a u v
y a u v
z a u v
Prolate spheroidal coordinates
tip surface: v = v0.
2
2 21 22 2 2 2 2 2
1 2 1 1 1 2 2 2
2
2 22 231 2
1 1 1 11 1
1 1
1 1
a a
a
1 2 3cosh , cos , u v
Static potential
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sinh sin cos ,
sinh sin sin ,
cosh cos
x a u v
y a u v
z a u v
Prolate spheroidal coordinates
1 2 3cosh , cos , u v
specify the shape of a hyperboloid tip by v = v0.
22
2 2
1 0
1
01 1
1 cos 1 cosln , ln
1 cos 2 1 cos
Vv vC C
v v
0 1
00
4
cos
CQ d
v
0
0
1
0
0
2 1 cosln
cos 1 cosv
Q vC
v
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/2
0/2
/2
0 0/2
0 0
1 ˆ ˆ
2 ˆ ˆ ˆ
4
indQ K n diw
n H n diw
Hiw
0 0
8indQ H
iw
Surface current in the back side
0 0 02
0
2 cos 1 cosln
1 cosind
ind
Q v vE
dC i d v
Induced current/charge
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ν0=π/6
0 0 02
0
2 cos 1 cosln
1 cosInd
v vE
i d v
LCM for a metal tip
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Slot antenna
/2
Half wave dipole antenna
Slot antenna
EH
Resonantly enhanced radiation
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THz slot antenna
Near field imaging of terahertz focusing onto rectangular aperturesD.S.Kim, P. Planken, Q.Park, Optics Express 16,20484, 2008
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Fourier transform terahertz imaging of E_x
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Energy Funneling: constant energy
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Substrate effect on aperture resonances in a thin metal filmJ. H. Kang, J.H. Choe, D.S. Kim, Q. Park, Optics Express 17,15652, 2009
Substrate effect
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Substrate effect
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ansres 2)75.025.0(
Resonance
23
322
)5.05.0(
)75.025.0(4
4
3
s
ssres n
n
ab
naT
Transmission at resonance
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Phased array antenna
X-Band Phased-Array Antenna
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r = 100 nm, p = 800 nm, t = 300 nm, Au on sapphire
SEMSEM
Extraordinary Optical TransmissionExtraordinary Optical Transmission
~ 5%!
T. W. Ebbesen et al., Nature 391, 667-669 (1998)
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Various slots for terahertz frequencies
SEM or Microscopic Images0.5 mm
At terahertz, metals are lossless: ~1/1000;wavelength: 0.1 mm~10 mm, skin depth=100 nm,
Shape resonance omni-directional terahertzfilters with near-unity transmittanceD.S. Kim et al. Opt. Expr. 14,1253,(2006)
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Perfect transmission
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Optical Yagi-Uda Antenna
Directional control of light by a nano-optical Yagi–Uda antennaTerukazu Kosako1, Yutaka Kadoya, Holger F. Hofmann, NATURE Photon, March, 2010
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Conclusions
Learn from analogies• receive and transmit• enhance and focus electric field• Directivity• Phased array
Learn from differences• can be active -- lasing• nonlinear optical processes• communicates with nano world:
- controlled chemistry/biology• more to come
Photonic crystal, metamaterial, optical antenna,…