metamateriali metamateriali ottici: “da veselago veselago ad...

XCVI Congresso Nazionale – SIF 23/09/10

UNIVERSITÀ DELLA CALABRIA

R. Bartolino, A. De Luca, G. Strangi

C. Umeton, R. Caputo, L. De Sio

MetamaterialiMetamateriali Ottici: Ottici: ““Da Da VeselagoVeselago ad oggiad oggi””



Cosa è un metamateriale?

Originates from a Greek word metameta: "after/beyond"

Metamaterials are artificially engineered materials possessing properties (e.g., mechanical, optical, electrical) that are not encountered in naturally occurring materials.

Metamaterials (MTMs), as well as photonic crystals (PC) are

composite metamaterials whose properties are not determined by the fundamental physical properties of their constituents but by the shape and distribution of specific patterns included in them.

MTMs have the unique property of having both the effective permittivity and the effectivepermeability negative.

The aim of the research is the theoretical understanding, analysis, development, fabrication and testing of MTMs, and also the investigation of their feasibility for applications.



Metamaterials:Pubblication /year & /subject area



k

2E 2Et2

n

V. G. Veselago:“The electrodynamics of substances with simultaneously negative value of ε

and μ,” Sov. Phys. Usp. 10, 509–514 (1968).

0))(( n



Meta-Materials

History:• Permittivity , permeability and index of refraction n negative• Reversal of Snell’s Law, perfect focusing, flat lenses, etc.• Impedance match z =√

and n = -1

•

>> a in Left Handed Materials, while a in PBG

Both PBG and LHM exhibit properties not found in naturally materials

Vision:• Understanding the physics and the exotic properties of LHMs• Perfect Lens. Near-field optical microscopy, nano-lithography• Wireless and optical communications. RF sensing.• Antenna and microwave device miniaturization________________________________

Breakthroughs and new concepts in materials processing at nanoscale Search for new materials that exhibit

< 0 at THz or optical regime



Negative materials

< 0 at optical wavelengths leads to important new optical phenomena.

< 0 is possible in many resonant magnetic systems.

What about < 0 and < 0?

Unfortunately, electric and magnetic resonances do not overlap in existing materials.

This restriction doesn’t exist for artificial materials!



Where are material resonances?

• Most electric resonances are THz or higher.

• For many metals, p occurs in the UV

• Magnetic systems typically have resonances through the GHz (FMR, AFR; e.g., Fe, permalloy, YIG)

• Some magnetic systems have resonances up to THz frequencies (e.g., MnF2 , FeF2 )

• Metals such as Ag and Au have regions where



Dalle microonde al visibile

Risultati nelle Microonde:- Materiali artificiali (tipo risonatori split-rings) che permettono di ottenere

lunghezze d’onda di risonanza più elevate, alti valori di capacità, basse perdite radiative e fattori di qualità molto elevati.- gestire frequenze comprese tra i 300 GHz e i 10 THz.

Per le onde piane che si propagano in tali metamateriali, il campo elettrico, campo magnetico e il vettore d'onda segue una regola left-hand.

- La Legge di Snell (n1 sinθ1 = n2 sinθ2 ) è ancora valida, ma con n2 negativo, i raggi saranno rifratti dallo stesso lato rispetto alla normale al materiale.- Lo Spostamento Doppler è rovesciato: cioè, una sorgente di

luce muovendosi verso un osservatore sembra ridurre la sua frequenza.- Il vettore di Poynting è antiparallelo alla velocità di fase.

Questo significa che a differenza di un normale materiale right- handed, i fronti dell'onda vengono a muoversi in direzione opposta al flusso di energia.

Frequenze ottiche:I metamateriali con n negativo hanno numerose proprietà sorprendenti:



Left-Handed Waves

If then is a right set of vectors:

If then is a left set of vectors:

0,0 kHE ,,

0,0 kHE ,,

E

k

H

E

k

H

Ec

Hk

Hc

Ek



Energy flux (Poynting vector):

Conventional (right-handed) medium

Left-handed medium

Energy flux in plane waves

grV

4S

SEk HSE kH SS

grV

phgr VV

HE4cS

kS

E

k

H

S

E

k

H

S kS

phgr VV



“Reversal” of Snell’s Law

1

21 2

PIMRHM

PIMRHM

PIMRHM

NIMLHM

(1) (2) (1) (2)

k

S k

S

1) Consequence: phase velocity (along k) and group velocity (along the Poynting vector) are in the same direction

2) In NIMs group and phase velocity are in opposite directions



RightRight--handedhanded LeftLeft--handedhanded

SourceSource SourceSource

n=1,5 n=-1

n=1

n=1

n=1

n=1

Courtesy of Maria Kafesaki (FORTH Crete)



Unusual refractive properties of NIMs

Light enters n > 0 material

deflection

Light enters n < 0 material

focusing

(“Veselago Lens”)

Surface waves make Veselago’s lens a super-lens! (Sir J. Pendry, 2000)

Open Cavity

PRL 102, 133902 (2009)



Metamateriali nel visibile (400-700 THz)

Nel range del visibile, affinchè un mezzo abbia delle caratteristiche di metamateriale, le strutture artificiali realizzate devono presentare taglie tipiche intorno a decine di nanometri, o meno.

Micro- e Nano-litografia/10l

This image was written using Dip-Pen Nanolithography, and imaged using lateral force microscopy mode of an atomic force microscope. Courtesy the Mirkin Group, Northwestern University.


UNIVERSITÀ DELLA CALABRIA EU Project 7FP - SEVENTH FRAMEWORK PROGRAMME

“METACHEM”Nanochemistry and Self-assembly

Routes to Metamaterials for Visible Light

Coordinating person: Dr. Philippe BAROIS

Participant: CNR - Prof. Roberto BartolinoDr. Antonio De Luca

UNICAL - Dr. Giuseppe StrangiProf. Carlo Versace

THEME 4Nanosciences, Nanotechnologies, Materials and

New Production Technologies

Collaborative Project Small-Scale Focused Research Projects

“NANOGOLD”Self-Organized Nanomaterials for

tailored optical and electrical properties

Coordinating person: Dr. Toralf Scharf

Participant: UNICAL - Prof. Cesare UmetonDr. Roberto Caputo,

Dr. Luciano De SioDr. Marco Castriota, Dr. Luigia Pezzi



Metachem Participants



Nanogold Participants



Obiettivi principali e concetti chiave

Main Objective:creating a radically new generation of metamaterials at infrared

and optical frequencies, based on the use of nano-chemistry and self-assembly of materials

Concept:Nano-scale chemistry and Self-assembly methods (either

spontaneous or directed), with the combined aid of theory and EM analysis methods, towards development of possible

technological devices with unusual properties.

METACHEM



Obiettivi principali e concetti chiave

Main Objective:The NANOGOLD project aims at the fabrication and application of bulk

electro-magnetic metamaterials. We will apply self-organization of organic- inorganic composite materials containing resonant entities.

Concept:To tune and optimize electromagnetic properties, resonance and interference

at different length scales will be implemented. In such a way we will obtain bulk optical metamaterials with unprecedented properties operating in spectral

domains appropriate for photonics that can be used in applications. Proof of principle devices will be the outcome of the project.

NANOGOLD



Reconfigurable metamaterials

The tunability

in the optical range can be

accomplished by incorporating electro-optically active materials such as liquid crystals into NIM structures.

Tuning or switching and other modulation processes can be performed electro–optically or all-

optically

To provide full operational functionality for optical NIM devices, they can be complemented by integrated tunable

elements.

The unique properties of liquid crystals such as:

• compatibility with almost NIMs; • broadband transparent 0.4 μm to 20 μm; • large optical birefringence;• and ultrahigh nonlinearities.

Appl. Phys. Lett. 97, 091101 (2010)


UNIVERSITÀ DELLA CALABRIA Nano-chimica e Self-assembly vs nanolitografia

J.-F. Dechézelles, et al. Colloids and Surfaces A: Physicochem. Eng. Aspects 343 (2009)

T. Placido, et al. Chem. Mat. 21 (18), (2009)

Nano-chimica

Self-assembly



Template assisted MTMs nell’infrarosso

Liu et al. Adv. Mater. 2008, 20, 2050–2054



Compensazione delle perdite in MTMs

Presenza di perdite ottiche in MTMs

Per riflessionePer assorbimento

(in termini di

grandi

n′′) (all’interfaccia)

Devono essere compensate attraverso l’inclusione di materiali di guadagno

Possibilità di essere soppresse attraverso un design ottimizzato di

un’impedenza ben accoppiata e/o dei gradienti delle proprietà EM

Capace di transferire energia ai polaritoni di superficie ed ai

plasmoni localizzati alla sup. nelle strutture metalliche, tramite

emissione stimolata

Dyes , quantum dots, semiconductor nanocrystals;



Metodologie proposte (nano-, meso- e macro-scala)

Approccio multiplo basato essenzialmente sull’inclusione di materiali di guadagno attraverso processi “guest-host” e funzionalizzazione per creare un guadagno stabile in metamateriali attivi

Guest Guest --

HostHostFunzionalizzazioneFunzionalizzazione



Demonstration of meta-EM properties

A work package will consists of two equally important overall aims:

to measure optical properties of fabricated metamaterials which imposes to extract relevant optical constants (permittivity, permeability, index of refraction) from these measurements.

to demonstrate and study extraordinary optical properties of metamaterials, such as negative optical phase, optical impedance matching and negative Snell’s angle.

PRL 102, 053901 (2009)PRB 79, 241104R 2009



“METACHEM”Nanochemistry and Self-assembly Routes to

Metamaterials for Visible Light

Coordinating person: Dr. Philippe BAROIS

Participant: CNR - Prof. Roberto BartolinoDr. Antonio De Luca

UNICAL - Dr. Giuseppe StrangiProf. Carlo Versace



Tecniche sperimentali utilizzate

FluorescenceConfocal Microscopy

TEM & SEM



Primi risultati su NPs core/shell dopate

FluorescenceFluorescence Quenching of Quenching of dyedye moleculesmoleculesnearnear Gold Gold CoreCore--ShellShell NpsNps

Au CoreAu Core57 57 ±±

7 7 nmnm

SilicaSilica ShellShell30 30 ±±

2 2 nmnm

h

d

C522B C522B DyeDye400 450 500 550 600 650 700 7500

1

2

3

4

5

6

7 A)

Wavelength (nm)

Nps C

ore-shell Absorbance (a.u.)

Fl

uore

scen

ce (a

rb. u

nits

) C522B Au-C522B

PumpPump @ 355nm@ 355nm




1400 1500 1600 1700 1800 19000.0

0.5

1.0

1.5

2.0

2.5

3.0

Log

Cou

nts

Chanels

Promt Decay Au@SiO2/OD Fit Au@SiO2/OD Decay OD in solution Fit OD in solution

Fluorescence

life time in presence

of GNPs

(from

2.9 10-9

to

1.8 10-9s)Fluorescence

life time in presence

of GNPs

(from

2.9 10-9

to

1.8 10-9s)




50 100 150 200 250 300 350 400 450 500

02468

101214161820

Tran

sm. I

nten

sity

(arb

. uni

ts)

Pump Energy (@355nm) (J)

B)

Trasparenza indotta

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

5

10

15

20

25

300 400 500 600 700 800

0

5

10

15

20

25

Sca

ttere

d In

tens

ity (a

rb.u

nits

)

Pump Energy (mJ)

A)

Inte

nsity

(arb

. uni

ts)

Wavelength (nm)

Aumento Scattering Rayleigh



Includiamo il guadagno nella shell

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

10

20

30

40

50

60

70

Threshold ~ 0.96 mJ

Sca

ttere

d In

tens

ity (a

rb. u

nits

)

Pump Energy (mJ)

h

EncapsulatedEncapsulated R6G R6G DyeDye/ or C500/ or C500

PumpPump @ 355nm@ 355nm

0 1 2 3 4 5 60.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

A)

@ 490 nm @ 500 nm @ 510 nm @ 520 nm @ 540 nm

Sca

ttere

d In

tens

ity (a

rb. u

nits

)

Pump Energy (mJ)

Misura Broadband



Includiamo il guadagno nella shell

0.0 0.5 1.0 1.5 2.0 2.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Nor

mal

ized

Inte

nsity

(arb

.uni

ts)

Pump Energy (mJ)

@460 nm @480 nm @500 nm @520 nm @540 nm @560 nm @580 nm

B)Out ofOut of

resonanceresonance

450 480 510 540 570 600 630 660 690 720 750 780 810

0

1

2

3

4

5

Abs_sam

ple_S1

Fluo

resc

ence

(arb

. uni

ts)

Wavelength (nm)

506 nmTrasparenza indotta (broadband)



“NANOGOLD”Self-Organized Nanomaterials for tailored optical and

electrical properties

Coordinating person: Dr. Toralf Scharf

Participant: UNICAL - Prof. Cesare UmetonDr. Roberto Caputo,

Dr. Luciano De SioDr. Marco Castriota, Dr. Luigia Pezzi



POLICRYPS as POLYMER MATRIX

POSSIBLE APPLICATIONS:

• OPTOFLUIDICS

• PHOTONIC SENSORS

• MAGNETIC DIFFRACTION

• DYE LASERS

• OPTICAL MICROCHANNELS

• WAVEGUIDE ARRAYS

•...........

• META-MATERIALS ?

PATENT APPLICATION N° CZ2009A000021

The final system is a periodic structure of polymer walls alternated to empty channels

AA PP

POLICRYPS: POlymer LIquid CRYstal Polymer Slides



Filling the template with NPsFilling the template with NPs



Filling the template with NPsFilling the template with NPs

Struttura 2D olografica



Meta-POLICRYPS with Silver NPs (~25nm)

400 500 600

0

10

20

30 MixtureT3T2

T0T1

Tran

smitt

ance

%

Wavelength (nm)



Possibili applicazioni: nanolaser plasmonici

Demonstration of a spaser-based nanolaserM. A. Noginov et al., Nature Vol 460 (2009)

Plasmon lasers at deep subwavelength scaleOulton et al. Nature, Vol 461 (2009)



Biosensori, superlenti ed invisibilità

BiosensorsMetamaterials can be used to provide more sensitive guiding modes (based on plasmon-mediated interaction between the inclusions which shows resonant excitation conditions).The metamaterial inclusions can be functionalised with receptors on theirsurface. If the matrix consists of nanoporous material it allows analytesto reach the receptor and the refractive index will be changed upon binding. The reflection spectrum depends on this refractive index.

SuperlensA superlens (or perfect lens) is a lens, which uses metamaterials to gobeyond the diffraction limit. The diffraction limit is an inherent limitation in conventional optical devices or lenses. A lens consisting of a negative index metamaterial could compensate for wave decay and could reconstructImages in the near field. In addition, both propagating and evanescent waves contribute to the resolution of the image and resolution underneath the diffraction limit will be possible.

CloakingA cloaking device is an advanced stealth technology that causes an object to be partially or wholly invisible to parts of the electromagnetic (EM) spectrum (at least one wavelength of EM emissions) Scientists are using metamaterials to bend light around an object.

Tags to store and process informationA remote detection via high-frequency electromagnetic fields will be possible due to the collective response of magnonic crystals at elevated frequencies.

Metamateriali Ottici: �“Da Veselago ad oggi”Cosa è un metamateriale?Metamaterials:Pubblication /year & /subject areaSlide Number 4Slide Number 5Negative materialsWhere are material resonances?Dalle microonde al visibileLeft-Handed WavesSlide Number 10Slide Number 11Slide Number 12Unusual refractive properties of NIMsMetamateriali nel visibile (400-700 THz)Slide Number 15Metachem ParticipantsNanogold ParticipantsObiettivi principali e concetti chiaveObiettivi principali e concetti chiaveReconfigurable metamaterialsNano-chimica e Self-assembly vs nanolitografiaTemplate assisted MTMs nell’infrarossoCompensazione delle perdite in MTMsMetodologie proposte (nano-, meso- e macro-scala)Demonstration of meta-EM propertiesSlide Number 26Tecniche sperimentali utilizzatePrimi risultati su NPs core/shell dopatePrimi risultati su NPs core/shell dopatePrimi risultati su NPs core/shell dopateIncludiamo il guadagno nella shellIncludiamo il guadagno nella shellSlide Number 33Slide Number 34Slide Number 35Slide Number 36Meta-POLICRYPS with Silver NPs (~25nm)Possibili applicazioni: nanolaser plasmoniciBiosensori, superlenti ed invisibilità

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