Post on 05-Aug-2020
Makoto Makoto KuwataKuwata--GonokamiGonokami
Department of Applied Physics, University of TokyoDepartment of Applied Physics, University of TokyoCRESTCREST, Japan Science and Technology Agency (JST), Japan Science and Technology Agency (JST)
http://www.gono.t.uhttp://www.gono.t.u--tokyo.ac.jptokyo.ac.jp
JST-DFG workshop on Nanoelectronics, 05-07.03.2008 in Aachen
Enhanced optical activity Enhanced optical activity in planar in planar chiralchiral nanonano--gratingsgratings
Univ. of TokyoUniv. of TokyoKuniaki KonishiNatsuki KandaNobuyoshi SaitoTomohiro SugimotoYusuke Ino
Univ. of Univ. of JoensuuJoensuuYuri SvirkoJari TurunenBenfeng BaiKonstantins JefimovsTuomas Vallius
Tampere UniversityTampere UniversityMartti Kauranen
CoCo--workersworkers
Gonokami Lab.Gonokami Lab.
Optical property of materialsOptical property of materials
~1Å=10-8m
Atom ・ Molecules
0.5μm=500nmλ
Artificial structures
Gonokami Lab.Gonokami Lab.
n : Refractive indexα: absorption coefficient
Control of optical property with artificial structuresControl of optical property with artificial structures
Photonic crystal
Ultra high-Q cavitySlow light
Metamaterial
Negative indexPerfect lens
2D metal structure
Extraordinary transmissionPolarization rotation with chirality
Polarization control withplanar chiral nano-gratings
Chirality and Optical activityOptical activity with 2D metal gratings Mechanism of giant optical activityApplication for the THz regionFuture prospect ~Chiral photonic crystal
OutlineOutline
Gonokami Lab.Gonokami Lab.
Polarization rotation in Polarization rotation in chiralchiral mediamedia
ChiralityChirality : The existence of the two forms with different handedness
Optical activityOptical activity
D = ˜ ε E + ig' k × E( )First-order spatial dispersion effect
Dependence of wave vector
,
kj jk k jki
k k i i
ED Ex
ε γ ∂= + + ⋅⋅⋅∂∑ ∑
NonNon--locality of optical response locality of optical response
Theorymicroscopic theory : Born (1915)
second order term of dispersion arizing from retardation of radiationpair of anisotropic dispersion oscillators: Kuhn (1929)quantum-mechanical theory: Rosenfeld (1928)polarizability theory: Gray(1916), de Mallemann(1927), Boys(1934)
Discovery1811 D.F. Arago quartz crystal1815 J. B. Biot Turpentine oil
Optical activityOptical activity
Polarization control withplanar chiral nano-gratings
Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of giant optical activityApplication for the THz regionFuture prospect ~Chiral photonic crystal
OutlineOutline
Gonokami Lab.Gonokami Lab.
PolarizationPolarization--sensitive diffraction in a sensitive diffraction in a chiralchiral gratinggrating
A. Papakostas et al, Phys. Rev. Lett. 90, 107404(2003)
Nonreciprocalpolarization
rotation?
2D periodic grating of structures without mirror symmetry
Diffracted reflection beam shows polarization rotation.
Right-twisted
Left-twisted
Sense of twist changes Sense of twist changes depending on the incident direction.depending on the incident direction.
Gonokami Lab.Gonokami Lab.
Optical activity with 2D Optical activity with 2D chiralitychirality ????
Giant Optical Activity in Metal Giant Optical Activity in Metal nanogratingsnanogratings
Giant optical activity(~104deg/mm)
T. Vallius et al., Appl. Phys. Lett. 83, 234 (2003)M.Kuwata-Gonokami et al., Phys. Rev. Lett. 95, 227401 (2005)
chiral metal nanogratings500nm
Cr:23nmAu :95nmCr:3nm
Silica substrate
Experimental setupExperimental setup
Intensity (transmissivity)Ellipticity anglePolarization azimuth angle
0 0I( 2 p ) I( p )A , H BI(0 ) I(0 )
Δ = =
Polarization modulation technique* (modulation frequency: ~50kHz)
Detection limit : ~0.002 degree*K. Sato,,” Jpn. J. Appl. Phys. 20, 2403 (1981)
θ
Α⊿
A sin( 2 B )Δ ΔΔ θ ϕ= + +
H HH A sin( 2 B )η ϕ= + +
Birefringencecaused by the non-equivalence
of the X- and Y-axes
Polarization effect due to the specific sense of twist(independent of ϕ)
At normal incidence
DDistinguishistinguish ooptical activity ptical activity fromfrom birefringencebirefringence at at normal incidencenormal incidence
Incident direction dependence
Right
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Angl
e [
deg
]
800700600Wavelength [nm]
Light incidence from front side from back side
From front side From back side
Left(chiral)
Right(chiral)
Cross(achiral)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Pol
ariz
atio
n az
imut
h ro
tatio
n θ
[deg
]
800700600500Wavelength [nm]
θL θA θR
Polarization rotation
M.Kuwata-Gonokami et al., Phys. Rev. Lett. 95, 227401 (2005)
Chirality-induced Giant optical activity
Giant Optical Activity in Metal Giant Optical Activity in Metal nanogratingsnanogratings
~104 deg./mm
Polarization control withplanar chiral nano-gratings
Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of the giant optical activityApplication for the THz regionFuture prospect ~Chiral photonic crystal
OutlineOutline
Gonokami Lab.Gonokami Lab.
Optical activity with doubleOptical activity with double--layered structureslayered structures
M. Decker et. al. Opt. Lett. 32, 856-858 (2007)
MgF2Au
Au
274nm
E. Plum et. al. Appl. Phys. Lett.90, 223113 (2007)
Optical activity of single-layer structure
is negligible?
ObjectiveObjective
To clarify the mechanism of giant optical activity of
single-layer chiral metal nanogratings
*Calculation of the electric field distribution at the metal surface
*Measurement of the transmission and polarization rotation spectra at oblique incidence
1
1
mx x
m
k iGc
ε εωε ε
= ±+
pω
sω1
1
mx
m
kc
ε εωε ε
=+
L
2GLπ
=
sinckω θ=
Metal
x
m
y
ε1ε
Excitation of surface Excitation of surface plasmonplasmon
Gonokami Lab.Gonokami Lab.
Calculation of the electric field Calculation of the electric field
Y-polarization 752nm
Metal-Substrate interface
500nm
Air-Metal interface
X
Y
Calculation method: B. Bai and L. Li, J. Opt. A: Pure Appl. Opt. 7, 783 (2005)101×101 grid
( ) ( ) ( ) ( )( ) χ γ= + ∇×⎡ ⎤⎣ ⎦P r r E r r E r
LightLight--matter coupling in nonmatter coupling in non--local medialocal media
Polarization with first-order spatial dispersion effect
nonlocalU≡( ) ( ) [ ]( )
0 0 0
d d d
U dz dz dzχ γ= = ⋅ + ∇×∫ ∫ ∫EP E E E ELight-matter coupling energy
Electric field strength at the interfaces
( )( )
/1 2
/1 2
0 d
d
z e
z d e
δ
δ
−
−
= = +
= = +
E E E
E E E d MetalSub.
E1
E2( ) ( ) ( ) ( ){ }
[ ](0) ( )( , ) 0 0nonlocal y
air sub
x y xU f d E E d E d E
d
δ= −
∝ ⋅ ×n E E
Eair
Esub
[ ]{ }
( 0) ( )
Reair sub
air sub air subx y y x
z z d
E E E E
⋅ = × = =
−
n E E
Non-parallel electric field at both interface
Calculation of the electric field Calculation of the electric field
Cross@752nmLeft@752nm
IncidentPolarization
( )( ) (0) ( )air subr dξ = ⋅ ×n E E
0.016
0.016
0.000
0.000
0.011
0.011
-0.011
-0.011
0≠total
0=total
DependencDependencee of of the the ChiralityChirality factor on the morphologyfactor on the morphology
Measurement at oblique Measurement at oblique incedenceincedence
We measured the transmission and polarization azimuth rotation at oblique incidence
( )( ) Asin 2 sin(4 )B C Dϕ θ ϕ ϕΔ = + + + +Fitting function
@720nmIncident angle
ψ=0°
ψ=+3°
ψ=+7°
DDistinguishistinguish ooptical activity ptical activity fromfrom birefringencebirefringence at at oblique incidenceoblique incidence
2
4
6
8
10
12
600700
800900
-8-6-4
-20
24
68
Tran
smitt
ance
(%)
Wavelength (nm)Inc
ident
angle
(deg
.)
2468
101214
600700
800900
-8-6-4
-20
24 6
8
Tran
smitt
ance
(%)
Wavelength (nm) Incid
ent a
ngle
(deg.)
Transmission spectra Transmission spectra
p-polarization s-polarization
1sp
1
mx x y
m
i jc
ε εωε ε
= = ± ±+
k k G G
Surface plasmon resonance condition
2 2 2i j+ =
2 2 1i j+ =
2 2 2i j+ =
2 2 1i j+ =
1sp
1
mx x y
m
i jc
ε εωε ε
= = ± ±+
k k G G
Surface plasmon resonance condition
2
4
6
8
10
12
600700
800900
-8-6-4
-20
24
68
Tran
smitt
ance
(%)
Wavelength (nm)Inc
ident
angle
(deg
.)
2468
101214
600700
800900
-8-6-4
-20
24 6
8
Tran
smitt
ance
(%)
Wavelength (nm) Incid
ent a
ngle
(deg.)
p-polarization s-polarization
2
1 2 2
1 2
( )sin
( )
s s
saψ ψ
ψ
λ ε λ εψ
ε λ ε⎛ ⎞
= −⎜ ⎟⎜ ⎟ +⎝ ⎠
1 2
1 2
( )sin
( )
p p
paψ ψ
ψ
λ ε λ εψ
ε λ ε= ±
+E E
Transmission spectra Transmission spectra
2
4
6
8
10
12
600700
800900
-8-6-4
-20
24
68
Tran
smitt
ance
(%)
Wavelength (nm)Inc
ident
angle
(deg
.)
-4
-2
0
2
600700
800900
-8-6
-4-2
02
46
8
Pola
rizat
ion
azim
uth
rota
tin (d
eg.)
Wavelength (nm) Incide
nt an
gle (d
eg.)
CComparisonomparison between Transmissionbetween Transmission and and PolarizaPolarizatiotion rotationn rotation spectraspectra
Transmission Polarization rotationp-polarizationp-polarization
kx (1/nm)
-0.0015-0.00
10-0.00
050.00000.000
50.001
00.001
5
Ene
rgy
(eV
)
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
kx (1/nm)
-0.0015-0.00
10-0.00
050.00000.000
50.001
00.001
5
Ene
rgy
(eV
)
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
Polarization control withplanar chiral nano-gratings
Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of giant optical activityApplication for the THz regionFuture prospect ~Chiral photonic crystal
OutlineOutline
Gonokami Lab.Gonokami Lab.
400 500 600 700nm
THz
1015
1μm 1mm
1012 109
1m
101010111014 1013
10cm1cm100μm10μm100nm
1016 frequency (Hz)
Electronics
wave length
ElectronicsPhotonicsPhotonics
The THz regionThe THz region
Semiconductors, Dielectrics, Superconductivity, Bioscience, …
Application to the THz regionApplication to the THz region
In the THz region, the metal thickness is much smaller than wavelength.
⇒ Field twist parameter is small.
100μm
side view Si substrate
Au 100 nm
complimentary double-layered structure
In complimentary structures,resonances are observed at same frequency(Babinet’s principle)
THz polarization rotation THz polarization rotation with complimentary with complimentary chiralchiral metal gratingsmetal gratings
0.6
0.4
0.2
0.0
Tran
smitt
ance
2.01.51.00.5Frequency (THz)
posi nega
Period: 100μm
Exs
am
Ex component correspond to polarization rotation
THz polarization rotation THz polarization rotation with complimentary with complimentary chiralchiral metal gratingsmetal gratings
permittivity polarization rotation
THz polarization rotation THz polarization rotation with complimentary with complimentary chiralchiral metal gratingsmetal gratings
SummarySummary
We visualized the relationship between surface plasmonresonance and the optical activity of chiral nanogratings.
We demonstrated that the chirality can be quantitatively described with the field twist parameter:
We demonstrated the polarization rotation of THz waves with complimentary double-layered chiral structures.
micro printing techniques such as ink-jet printing
( )2unit cell
1 air sub dxdyA
⋅ ×∫ n E EE
・K. Konishi, T. Sugimoto, B. Bai, Y. Svirko, and M. Kuwata-Gonokami , Opt. Express 15, 9575-9583 (2007).Effect of surface plasmon resonance on the optical activity of chiral metal nanogratings
・N. Kanda, K. Konishi, and M. Kuwata-Gonokami, Opt. Ex. 15, 11117 (2007)Terahertz wave polarization rotation with double layered metal grating of complimentary chiral patterns
Polarization control withplanar chiral nano-gratings
Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of giant optical activityApplication for the THz regionFuture prospect ~Chiral photonic crystal
OutlineOutline
Gonokami Lab.Gonokami Lab.
Future prospectFuture prospect
larger rotation higher transmittancesmaller birefringence
16
14
12
10
8
6
4
Tran
smis
sion
(%)
900850800750700650600550
Wavelength (nm)
Right Left Achiral
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
Pola
riza
tion
rota
tion [
deg.
]
150100500
Input polarization azimuth [deg.]
measurement point sincurve fitting offset
Opticalactivity
Left@575nm
Transmittance
Dielectric chiral nanograteng(2D chiral pthotonic crystal)
birefringence
Gonokami Lab.Gonokami Lab.
Next challenges
Polarization rotation in chiral mediaPolarization-sensitive diffraction in a chiral gratingGiant Optical Activity in Metal nanogratingsExperimental setupGiant Optical Activity in Metal nanogratingsOptical activity with double-layered structuresObjectiveMeasurement at oblique incedenceTransmission spectra Comparison between Transmission and Polarization rotation spectraApplication to the THz regionSummaryFuture prospect