Enhanced optical activity in planar chiral nano-gratings...Optical activity with double-layered structures M. Decker et. al. Opt. Lett. 32, 856-858 (2007) MgF 2 Au Au 274nm E. Plum

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


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


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


Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of giant optical activityApplication for the THz regionFuture prospect ～Chiral photonic crystal

OutlineOutline


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.


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


Chirality and Optical activityOptical activity with 2D metal gratingsMechanism of the giant optical activityApplication for the THz regionFuture prospect ～Chiral photonic crystal

OutlineOutline


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


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



OutlineOutline


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


permittivity polarization rotation


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



OutlineOutline


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


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

Documents

Enhanced optical activity in planar chiral nano-gratings...Optical activity with double-layered structures M. Decker et. al. Opt. Lett. 32, 856-858 (2007) MgF 2 Au Au 274nm E. Plum