Q-Han Park Korea Univ.
description
Transcript of Q-Han Park Korea Univ.
Q-Han Park
Korea Univ.
APSE 2010
1
The 4th Yamada Symposium on Advanced Photons and Science Evolution 2010
EM field enhancement - antennas
Marconi's antenna system at Poldhu Cornwall, December
1901.
Monopole antenna
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.
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
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
Optical antenna - sensor
Optical monopole antenna Single molecule fluorescence
Excitation 514 nm
Fluorescence 570 nm
Emission control by a monopole antenna
Optical antenna as a vector field probe
D.S.Kim, Q.Park. et al, Nature Photonics 1, 53 (2007)
• 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
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
Optical antenna - bowtie
Bow tie antenna – EUV generation
S.W.Kim et al, Nature 2008
Bow tie antenna
S.W.Kim et al, Nature 2008
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
EM field enhancement by nano slit
Electric field enhancement: ~1,000 with λ /10,000 size gap
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
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
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
Local capacitor model
-zone
Local Capacitor Model for Plasmonic Electric Field EnhancementQ.Park Phys. Rev. Lett.102, 093906, 2009
Slit
-zone capacitance
Static capacitance restricted to the -zone
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
2IndEiav
width = 0.00067 thickness = 0.002
Enhanced electric field inside the gap
Real metal case
Good qualitative agreement
x
y
zy-polarized incident light
Metal tip near metal surface
Intensity profile near metal tip (FDTD calculation:xy-cut)
xz-cut
Bowtie
Spheroidal prolate coordinates Field enhancement
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
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
/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
ν0=π/6
0 0 02
0
2 cos 1 cosln
1 cosInd
v vE
i d v
LCM for a metal tip
Slot antenna
/2
Half wave dipole antenna
Slot antenna
EH
Resonantly enhanced radiation
THz slot antenna
Near field imaging of terahertz focusing onto rectangular aperturesD.S.Kim, P. Planken, Q.Park, Optics Express 16,20484, 2008
Fourier transform terahertz imaging of E_x
Energy Funneling: constant energy
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
Substrate effect
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
Phased array antenna
X-Band Phased-Array Antenna
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)
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)
Perfect transmission
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
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,…