赤外吸収メタマテリアル

理化学研究所

田中メタマテリアル研究室

理化学研究所

光量子工学研究領域

東京工業大学!

田中拓男

第６回可視赤外線観測装置技術WS

November/24/ʼ16 11:30-12:00

Metamaterials
negative index/negative refraction
cloaking

perfect lens/ super lens

メタマテリアル

波長より細かな（サブ波長）人工構造を用いて，物質の光学特性(n, ε, μ)を操作した人工物質

Discrepancy between extinction coeﬃcient and absorption
Index of refraction

Highly absorptive material

N = n − ik
extinction
coefficient

Fresnel formula(from air to matter.)

N −1
R=N +12!

Large extinction coef.
!

contradiction

Highly reﬂection!

Low absorption
e.g.：Au
Reflection

N = 1.85 - 21.7i at λ = 3 µm
~ 98% reflection
Only 2% absorption

Absorption

IncidentlightGoldSci. Rep. 5, 12570 (2015).

Metamaterial absorber・Nano scale structures on ﬂat metal ﬁlm (no transmission)・Impedance matching for no reﬂection➡ Perfect absorption by ultra-thin layer

反射＋透過＋吸収＋（散乱）=1.0
n - ikNo reﬂection

PerfectAbsorption
IncidentlightOutline
光を吸収する技術と，その応用!

１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．(Fabrication technique for 3D Metamterials)

Dark plasmons

1st mode(dipole mode)
Radiation (Loss)
Light

Excitation○

Q-factorlowDark plasmons

2nd mode

Excitation

X

Q-factorhighDark plasmons

Bright plasmons

Excitation○

Dark plasmons

X(No radiation loss)

Q-factor

lowhighOutline
１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．(Fabrication technique for 3D Metamterials)

No peak(dark mode)

E+-+EEE

E

Excitation
Radiation

Hi-Q
couplin

Low-Q

EIT

No modePlasmonic induced transparency

Fabrication of dark metamaterial
1.Substrate cleaning

2.Electron beam patterning

4.Sputtering

5.Lift-oﬀ

SEM images

3.Resist coat

RodE

”C”shapeRod”C”shapeRod”C”shape
Polarization

Rod”IC””C”shape
“IC”

“I”

“C”

“IC”
Polarization

Polarization

dark modeno plasmon mode

Polarization

Rod770nm”C”shape“IC”

Numerical results (by FEM)

EE

at 750nm

at 810nm

JTime resolved Photoemission Electron Microscopy

fs-laser(normal)
fs-laser(oblique, 74o)Collaboration with Prof. Misawa & Ueno
in Hokkaido Univ.
4nm spatial resolution
SP propagates on Au surface

Polarization

PEEM@UVRod”C”shape“IC”

Polarization

PEEM@770nm

Rod”C”shape“IC”(almost) No radiation

Outline
１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．(Fabrication technique for 3D Metamterials)

Metamaterial absorber

Discrepancy between extinction coeﬃcient and absorption
Index of refraction

Highly absorptive material

N = n − ik
extinction
coefficient

Fresnel formula(from air to matter.)

N −1
R=N +12!

Large extinction coef.
!

contradiction

Highly reﬂection!

Low absorption
e.g.：Au
Reflection

N = 1.85 - 21.7i at λ = 3 µm
~ 98% reflection
Only 2% absorption

Absorption

IncidentlightGold

Metamaterial absorberSci. Rep. 5, 12570 (2015).

・Nano scale structures on ﬂat metal ﬁlm (no transmission)・Impedance matching for no reﬂection➡ Perfect absorption by ultra-thin layern - ikNo reﬂectionPerfectAbsorption
Incidentlight30 x 30mm2w/Λ = 1.5/3.0µm

Au
MgF2
Au
SiO225µm

Sci. Rep. 5, 12570 (2015).

Metamaterial absorber

Nano scale structures on ﬂat metal ﬁlm (no transmission)
Impedance matching for non-reﬂection➡ Perfect absorption
Bare Au

Meta-Surface

Standing Wave

Non Reflection
Au(50nm)

MgF2(90nm)-+ Au
Λ = 6µm+-3µm+ Au

Λ = 6µm

7

Outline
１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．(Fabrication technique for 3D Metamterials)

Finger print regionReflection Absorption Spectrometry (RAS)
Metals-polp-pol[1] A.Gole et al., Langmuir 20, 7117 (2004).

16-Mercaptohexadecanoic acidC–H stretching vibrational modes
2850–2863 cm−1 (symmetric)
2916–2936 cm−1 (asymmetric)

Recipe for 16-Mercaptohexadecanoic acid SAM
1) Au substrate immersed in a 10-3M solution in ethanol for 36 h.
!
2) Then, rinsed in ethanol and dried with N2 gas.
!
3) Characterized with FT-IR (Reflection Absorption Spectroscopy)

Au/Cr (100/5nm)
SiO2

Reflection Absorption Spectrometry (RAS)
Metals-pol

p-pol

100

104

Reflectivity

103.5

99

103

111313-5 w/16-MHA at ras80deg.

C–H stretching vibrational modes
2850–2863 cm−1 (symmetric)
2916–2936 cm−1 (asymmetric)

1.0%

102.5

98

102

101.5

3000

2000

1000

F. Neubrech et. al, Phys. Rev. Lett. 101, 157403 (2008)

SEIRA (Surface enhancement IR absorption) using coupling of plasmon withvibrational mode of molecule.

CH3(CH3)16CH2SH

S/B = Signal / Background
Enhancement

×Suppression○Resonant Coupling Absorption Spectroscopysuppression● Background suppression● Resonantly enhanced signal● Zepto-mol sensitivity

Sci. Rep. 5, 12570 (2015).

30 x 30mm2w/Λ = 1.5/3.0µm

Au
MgF2
Au
SiO225µm

IR characterization

ExperimentSci. Rep. 5, 12570 (2015).

Numerical
C–H stretching vibrational modes
2850–2863 cm−1 (symmetric)
2916–2936 cm−1 (asymmetric)

Sci. Rep. 5, 12570 (2015).

30 x 30mm2w/Λ = 1.5/3.0µm

25µm

16-MHA
Au
MgF2
Au
SiO2

Au
MgF2
Au
SiO2

on bare Au

100104103.599

103

111313-5 w/16-MHA at ras80deg.

C–H stretching vibrational modes
2850–2863 cm−1 (symmetric)
2916–2936 cm−1 (asymmetric)

1.0%

102.5

98

102

101.5

on meta-absorber

Au
MgF2
Au
SiO2

Reflectance [%]16-MHA

100

3000

2000

1000

80
60
40

2nd

1st

20
0

3000

2500

2000
1500
Frequency [cm-1]

1000

Sci. Rep. 5, 12570 (2015).

Absorption Properties

Reflectance [%]only flat Au film

Wavenumber [cm-1]

Sensitivity = 1.8atto(10-18) molin beam spot

Numerical calculation"%ω p2ε (ω ) = ε s $$1+ 2''2# ω 0 − ω + i2γω &0.9

9.0

0.880

8.00.77.0

Reflection

6.0

0.5

5.00.440

4.00.30083

2nd mode

0.660

SPP

3.00.220

2.00.11.0000063 2600

34000043 2800

16-MHA (t = 2nm)

noitcelfeRReflectance

16-MHA modeled using Lorentz dielectric function:!
!
where εs = 1.0, ωp = 300THz, ω0 = 95THz (3166cm-1), γ = 0.1THz]mn[ 04 = 2T & ]im[ 5.R1 for= WRRWro=f 1.5
R [mi] & T2 = 40 [nm]11001θin = 70deg.

3200
3000
Frequency [cm-1]

0023 3000]1−mc[ ycneuqerF

2800

0003 3200
0082 3400
Frequency [cm−1]00062 3600

1.5µm

3µm

3800

Au (t = 50nm)
MgF2 (t = 30nm)
Au (t = 200nm)
SiO2

Nano fluidic device with metamaterial absorber

Flow
Applying pressure

Cross-section of nanochannel

Au
MgF2
Au
SiO2

Upper substrate

Flow

Au square-disk
Au mirror
molecules
Lower substrate|H|!

2908cm-1
2934cm-1

Ice

Bulk water

d=70nmChannel depth = 70 nm!
Channel depth = 15 nm!

Wavenumber [cm-1]d=15nm

Absorption engineering by metal nano structures

Original Data

By aluminum structure

180#

100#
260#

420#

Outline
１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．Fabrication technique for 3D Metamterials

Self-folding of Bi-layer Metallic Structures
Self-folding

Tensile stress
Au
Ni
Fixed
end

Si

Self-folding of Bi-layer Metallic Structures

Adv. Opt. Mater 2014
nature ”Research Highlights” 515

Self-folding

Tensile stress
Au
Ni
Fixed
endSiSelf-folding of Bi-layer Metallic Structures

Adv. Opt. Mater 2014
nature ”Research Highlights” 515

Self-folding

Tensile stressAuNi
FixedendSi

Optical Characterization

Experiment

Simulation

asymmetric mode

● Magnetic (LC) resonance at f = 30 THz (λ = 10 µm)● Excellent agreement b/t the experiment & simulation

SRRアレイの異方性

単一共振器の異方性

εμξ

ｎn~0.3

Retrieved Effective Optical Parameters

n2 = µ1.90.35● Lorentz-like responses at f = 30 THz● n largely swings from 0.35 to 1.92

Isotropic metamaterial by stress tension assisted EB litho.
an example of combination of top-down and bottom-up

垂直入射，θ依存性

入射(φ)角依存性

Conclusion
１．Non-radiative surface plasmon (Dark plasmon)
２．Dark plasmonic metamaterials for absorber!

３．Application of dark metamaterials for molecularsensing!

４．(Fabrication technique for 3D Metamterials)