ORGANIC & HYBRID PHOTONIC CRYSTALS - unipr.itfilm (Ø 260 nm) • Photons having energy within the PBG cannot propagate into the PhC being backward diffracted. • Dielectric lattice

$Page 1: ORGANIC & HYBRID PHOTONIC CRYSTALS - unipr.itfilm (Ø 260 nm) • Photons having energy within the PBG cannot propagate into the PhC being backward diffracted. • Dielectric lattice$
D. Comoretto ORGANIC & HYBRID PHOTONIC CRYSTALS GISR2014, Parma, 9-11 June 2014

ORGANIC & HYBRID PHOTONIC CRYSTALS

[email protected]

Davide Comoretto

Dipartimento di Chimica e Chimica Industriale

Università degli Studi di Genova

via Dodecaneso 31

16146 Genova (Italy)



GNSR – the former GISR


TALK OUTLINE

• Introduction to Photonic Crystals

• All-Polymer Distributed Bragg Reflector Sensors

• Fluorescence Enhancement in Engineered Opals

• Bloch Surface Waves: Polaritons & Light Localization

• Hybrid Plasmonic-Photonic systems (2D-3D)

500 550 600 650 700 750

Flu

ore

scen

ce (

a.u

.)

Wavelength (nm)

Microspheres

OpalGold crescent@opal

• Polymer & Hybrid Microcavities for Lasing & Switching 500 525 550 575 600 625 650

PL

(a

rb.

un

its)

Wavelength (nm)

Incident light Reflected light


w

1D 2D 3D

Photon in

vacuum

Photon in a periodic

dielectric structure Free electron

Electron in a

crystal lattice

dj >> a0 (Bohr’s radius)

dj ~ l of visible light

d2 d2

d3 d1 d1 d1

The dielectric constant (e)

must be considered

(dielectric lattice)

E

k k

E

2k2

2 m

E

k

m2

k=E

22 w ck

w

k

kc=w

PHOTONIC CRYSTALS


400 450 500 550 600 650 700 750

0,0

0,1

0,2

0,3

Re

fl./T

rans.

Wavelength (nm)

R

T

polystyrene opal

film (Ø 260 nm)

• Photons having energy within the PBG cannot

propagate into the PhC being backward

diffracted.

• Dielectric lattice geometry and dielectric

contrast allow to engineer the PBG. E. Pavarini, Phys. Rev. B72, 045102 (05)

OPTICAL EFFECTS IN PHOTONIC CRYSTALS

STRONG LIGHT DIFFRACTION

EFFECTS

• Bright colors.

• Iridescence (color change by

orientation).

• Chromatic effects depend on the

dielectric environment - applied stimuli.

𝐷 = 𝒂2

3 𝝀 = 2𝑫 𝒏𝒆𝒇𝒇

𝟐 − 𝑠𝑖𝑛2𝜽


Peacock feathers Sea mouse

NATURAL PHOTONIC CRYSTALS

Photonic berries

(Elaeocarpus fruits)


PHOTONIC FOODS

PhotonicTM Chocolate, © morphotonix


PHOTONIC CRYSTALS GROWTH

Inorganic materials

TOP-DOWN

Organic materials

BOTTOM-UP

F. Müller et al., J. Porous Mater. 7, 1/2/3, S. 201 (00) E.L. Thomas group. Polymer 44, 6725 (03)


POLYMER PHOTONIC CRYSTALS @ WORK

E.L. Thomas group, ACS Nano 6, 8933 (12) http://www.thegenteel.com/articles/design/rainbow-winters

http://www.np.phy.cam.ac.uk/research-themes/polymer-opals

Adv. Engin. Mater. 15, 948 (13)

Polymer photonic crystal sensors Polymer opals fabric

http://www.thegenteel.com/articles/design/rainbow-winters










PHOTONIC CRYSTAL IN GENOVA

Ø 222 nm

V. Robbiano et al. Adv. Optical Mater. 1, 389 (13)

A. Belardini et al. Adv. Optical Mater. 2, 208 (14)

Opal Photonic Crystals (3D)

Distributed Bragg Reflectors

(DBR) Microcavity

L. Berti, J. Phys. Chem. C114, 2403 (10)

D. Antonioli et al., Polym. Int. 4206 (12)

K. Sparnacci et al., J. Nanomat. 2012, 980541 (12)

D. Comoretto et al. Polym. Comp., 34, 1443 (13)

F. Di Stasio et al. APL. Materials 1, 042116 (13)

L. Frezza et al., J. Phys. Chem. C115, 19939 (11)

G. Canazza et al. Laser Phys. Lett. 11, 035804 (14)

S. Pirrotta et al., Appl. Phys. Lett. 104, 051111 (14)

C. Toccafondi et al. J. Mater. Chem. 2, 4692 (14)

2D microsphere arrays

Polymer multilayers and microcavities (1D)


TALK OUTLINE






500 550 600 650 700 750

Flu

ore

scen

ce (

a.u

.)

Wavelength (nm)

Microspheres



PL

(a

rb.

un

its)

Wavelength (nm)



HYBRID PLASMONIC-PHOTONIC SYSTEMS

20000 18000 16000 14000 12000 100000.00

0.05

0.10

0.15

0.20

0.25500 600 700 800 900 1000

Reflecta

nce (

TM

)

Wavenumber (cm-1)

260nm

Wavelength (nm)

Bare Opals: Phys. Rev. B72, 045102 (05)

Gold nanoaprticles doped opals

Optical Switching: Adv. Funct. Mater. 17, 2779 (07)

Light Localization: J. Phys. Chem. C, 112, 6293 (08)

Fine Band Gap Tuning: Appl. Phys. Lett. 93, 091111 (08)

Opals doped with AuNP Nanocrescents@Opals

V. Robbiano et al. Adv. Optical Mater. 1, 389 (13))



300 400 500 600 700 800 900 1000

0

20

40

60

80

100

0

20

40

60

80

100

Refle

cta

nce (%

)

Tra

nsm

itta

nce (

%)

Wavelength (nm)

MICROSPHERE MONOLAYERS

340 nm

V. Robbiano et al. Adv. Optical Mater. 1, 389 (13)


NANOCRESCENTS ON MONOLAYER

AFM topography

(intermitted contact)

AFM

(phase-contrast)

SEM

(secondary electrons)

SEM

(back-scattering)

300 nm

Ø 260 nm

• Grazing (20°) evaporation

incidence.

• Polycrystalline Au.

• Disconnected crescents.

• Strongly anisotropical system

(long axis: diameter; short axis:

arc; variable cortex thickness).

• Curved crescents.

• The morphological analysis suggests the assignment of plasmonic modes


400 600 800 1000 1200 1400 1600

0

10

20

30

40

50

60

70

80

90

100

Tra

nsm

itta

nce (

%)

Wavelength (nm)

s

p

E-field

E-field

OPTICAL RESPONSE OF NANOCRESCENTS

a=340 nm

HE

V. Robbiano et al., Adv. Optical Mater. 1, 389 (13)


MONOLAYER vs OPAL vs NANOCRESCENTS

400 500 600 700 800 900 10001100

Wavelength (nm)

monolayer

opal340 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

monolayer

opal

426 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

s

p(e), 340 nm

400 500 600 700 800 900 100011000

20

40

60

80

100

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

monolayer

opal260 nm

400 500 600 700 800 900 100011000

20

40

60

80

100

Tra

nsm

itta

nce

Wavelength (nm)

s

p(d), 260 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

s

p(f), 426 nm

HE

HE

HE

Opal stop band

Van Hove-like

modes

Forward diffraction


SCALING PROPERTIES OF NANOCRESCENTS

240 280 320 360 400 440

600

800

1000

1200

1400

1600

LS

PR

(nm

)

Sphere Diameter (nm)

600

800

1000

1200

1400

1600 Opal S

top B

and (n

m)

HE

• Opal stop band and LSPR along the long axis have almost the same scaling thus

making impossible their spectral overlap.

• Resonances along the nanocrescent short axis and the HE have a reduced

dependence on microsphere diameter:

• Overlap is expected in particular for light polarised along the short

nanocrescent axis (S).

opal


400 500 600 700 800 900 1000 11000

20

40

60

80

Tra

nsm

itta

nce

(a.u

.)

Wavelength (nm)

260 nm

400 500 600 700 800 900 1000 1100

340 nm

Wavelength (nm)

400 500 600 700 800 900 1000 1100

Wavelength (nm)

426 nm

OPALS vs NANOCRESCENTS@OPALS OPALS

NANOCRESCENTS @ OPALS

400 500 600 700 800 900 100011000

10

20

30

40

50

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

p

s

260 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

p

s340 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

p

s426 nm

• depending on microsphere diameter and light polarization (S), a “mixing” between the PhC modes and

the LSPR can be suggested.


400 500 600 700 800 900 10001100

Wavelength (nm)

s

p340 nm

NANOCRESCENTS vs NANOCRESCENTS@OPAL

400 500 600 700 800 900 100011000

10

20

30

40

50

Tra

nsm

itta

nce (

%)

Wavelength (nm)

p

s

260 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

p

s340 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

p

s426 nm

400 500 600 700 800 900 100011000

20

40

60

80

100

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

s

p260 nm

400 500 600 700 800 900 10001100

Wavelength (nm)

s

p426 nm

HE HE HE

NANOCRESCENTS



OPALS & NANOCRESCENTS@OPALS

300 400 500 600 700 800 90010000

10

20

30

40

50

60260 nm (a)

Wavelength (nm)

An

gle

(d

eg

)

400 500 600 700 800 90010001100

426 nm (c)

Wavelength (nm)

300 400 500 600 700 800 90010000

10

20

30

40

50

60

Wavelength (nm)

An

gle

(d

eg

)

260 nm (d)

400 500 600 700 800 90010001100

Wavelength (nm)

340 nm (e)

400 500 600 700 800 90010001100

Wavelength (nm)

426 nm (f)

OPALS


400 500 600 700 800 90010001100

340 nm (b)

Wavelength (nm)


DISPERSION PROPERTIES OF HYBRID SYSTEM

0 8 16 24 32 40500

520

540

560

580

600

neff

=1,39 Bare Opal

neff

=1,38 HybridWa

ve

len

gth

(n

m)

Angle (deg)

(a)

260 nm

0 8 16 24 32 40650

675

700

725

750

775

800

neff

=1,41 Bare Opal

neff

=? Hybrid

Wa

ve

lng

th (

nm

)

Angle (deg)

340 nm

0 8 16 24 32 40800

850

900

950

1000

neff=1,40 Bare Opal

neff=1,35 Hybrid

Wa

ve

len

gth

(n

m)

Angle (deg)

426 nm

• Photons lose their wavevector dependence by transferring it to localised plasmons.

• An HYBRID PLASMONIC-PHOTONIC EXCITATION is created.

• Spectral Shift

• Unchanged

dispersion

• Spectral shift

• Strongly modified

dispersion

• No spectral

shift

• Unchanged

dispersion

𝑚𝜆 = 2𝐷 𝑛𝑒𝑓𝑓2 − 𝑠𝑖𝑛2𝜗

𝐷 = 𝑎2

3


SECOND HARMONIC GENERATION CIRCULAR

DICHROISM IN NANOCRESCENTS


0

20

40

60

80

-40 -20 0 20 40

Sample 1 p-pSample 2 p-pSample 3 p-p

Incidence anlge (deg)S

HG

(arb

. u.)

0

20

40

60

80

100

-40 -20 0 20 40

Sample 1 p-sSample 2 p-s Sample 3 p-s

Incidence angle (deg)

SH

G (

arb

. u.)

0

50

100

-60 -45 -30 -15 0 15 30 45 600

2

4Sample 2 p-sSample 4 p-sSample 5 p-p


SH

G (

arb

. un.)

-2

-1

0

1

2

-40 -20 0 20 40

Sample 1 shg-cd pSample 2 shg-cd pSample 3 shg-cd p


SH

G-C

D

-2

-1

0

1

2

-40 -20 0 20 40

Sample 1 shg-cd sSample 2 shg-cd sSample 3 shg-cd s


SH

G-C

D

FIRST HARMONIC SECOND HARMONIC

s or p pol. light

ap pol. light

or left/right handed

circ. pol light

(a) (b)

(c) (d)

(e) (f)

p(w):s(2w)

Sample 2: 340 nm + gold

nanocrescents

Sample 4: 340 nm

nanocrescents

Sample 5: gold film

Anisotropical response

strongly dependent on

the microsphere

diameter

0

20

40

60

80

-40 -20 0 20 40


Incidence anlge (deg)

SH

G (

arb

. u.)

0

20

40

60

80

100

-40 -20 0 20 40



SH

G (

arb

. u.)

0

50

100

-60 -45 -30 -15 0 15 30 45 600

2



SH

G (

arb

. un.)

-2

-1

0

1

2

-40 -20 0 20 40



SH

G-C

D

-2

-1

0

1

2

-40 -20 0 20 40



SH

G-C

D


s or p pol. light

ap pol. light


circ. pol light

(a) (b)

(c) (d)

(e) (f)

w=800 nm 2w=400 nm


SECOND HARMONIC GENERATION CIRCULAR

DICHROISM IN NANOCRESCENTS

Au fluxdirection

Au fluxdirection

Au fluxdirection

Au fluxdirection

B1A C B2

(a)

(b)

(c) (d)

0

20

40

60

80

100

400 500 600 700 800

Sample 1 no-gold CALC.Sample 1 CALC.Sample 1 EXPER.Sample 1 || CALC.Sample 1 || EXPER.

wavelength (nm)

Tra

nsm

issio

n (

%)

0

20

40

60

80

100

400 500 600 700 800

Sample 2 no-gold CALC.Sample 2 CALC.Sample 2 EXPER.Sample 2 || CALC.Sample 2 || EXPER.

wavelength (nm)

Tra

nsm

issio

n (

%)

0

20

40

60

80

100

400 500 600 700 800 900

Sample 3 no-gold CALC. Sample 3 CALC.Sample 3 EXPER.Sample 3 || CALC. Sample 3 || EXPER.

wavelength (nm)

Tra

nsm

issio

n (

%)


0

20

40

60

80

-40 -20 0 20 40


Incidence anlge (deg)

SH

G (

arb

. u.)

0

20

40

60

80

100

-40 -20 0 20 40



SH

G (

arb

. u.)

0

50

100

-60 -45 -30 -15 0 15 30 45 600

2



SH

G (

arb

. un.)

-2

-1

0

1

2

-40 -20 0 20 40



SH

G-C

D

-2

-1

0

1

2

-40 -20 0 20 40



SH

G-C

D


s or p pol. light

ap pol. light


circ. pol light

(a) (b)

(c) (d)

(e) (f)s(2w)

Sample 1: 260 nm + gold nanocrescents



p(2w)

𝑆𝐻𝐺−𝐶𝐷 =𝐼𝐿2𝜔 − 𝐼𝑅

2𝜔

(𝐼𝐿2𝜔 + 𝐼𝑅

2𝜔) 2

260 nm, chirality q=0° 340 nm, chirality q=0° 426 nm, chirality only for q0°


TALK OUTLINE






500 550 600 650 700 750

Flu

ore

scen

ce (

a.u

.)

Wavelength (nm)

Microspheres



PL

(a

rb.

un

its)

Wavelength (nm)



Applying solution Rotating Drying

Polystyrene

(PS, n= 1,59)

Cellulose Acetate

(CA, n= 1,47) Poly(vinyl carbazole)

(PVK, n=1.67)

SPIN CAST 1D POLYMER PHOTONIC CRYSTALS

Fluorescence

Poly(vinyl alcohol)

(PVA, n= 1,5)

SNN

Poly(9,9-di-n-octylfluorene-alt-

benzothiadiazole) (F8BT)

C. Bertarelli - POLIMI G. Galli - PISA


G. Canazza et al. Laser Physics Lett. 11, 035804 (14).

Poly(phenylene-oxide)

(PPO, n= 1,57) G. Guerra - Salerno

Branched

Poly(vinylsulfide)

(n> 1,7)

B. Voit - Dresden

CdSe:CdS

dot@rod

Photochromism


For l/4 condition

∆𝐸 =4

𝜋𝐸

𝑛1 − 𝑛2𝑛1 + 𝑛2

• 1D polymer PhC

Multilayers = Distributed

Bragg Reflectors (DBR).

• Increased dielectric contrast

provides wider band gap and

more intense reflection peak.

PPO:CA 1.57:1.47

𝑑1 =𝜆

4𝑛1= 𝑑2 =

𝜆

4𝑛2

𝑅 = 1 − 4𝑛1𝑛2

2𝑁

500 550 600 650 700 750 800

0

10

20

30

40

50

60

70

80

90

100

Reflecta

nce (

%)

Wavelength (nm)

5 bi-layers

10 bi-layers

15 bi-layers

20 bi-layers

25 bi-layers



0

20

40

60

80

100

Re

flecta

nce (

%)

10000 15000 20000 25000 30000 350000

20

40

60

80

100

Wavenumbers (cm-1)

1000800 600 400 Wavelength (nm)

For l/4 condition

∆𝐸 =4

𝜋𝐸

𝑛1 − 𝑛2𝑛1 + 𝑛2

• 1D polymer PhC

Multilayers = Distributed

Bragg Reflectors (DBR).

• Increased dielectric contrast

provides wider band gap and

more intense reflection peak.

PS:CA 1.59:1.47

PVK:CA 1.67:1.47

𝑑1 =𝜆

4𝑛1= 𝑑2 =

𝜆

4𝑛2

𝑅 = 1 − 4𝑛1𝑛2

2𝑁



DBR: X-RAY REFLECTANCE SPECTROSCOPY

PVK: Thickness 62.4±0.1 nm; roughness 0,29±0.01 nm

PS: Thickness 112.1±0.1 nm; roughness 0,26±0.01 nm

Thanks to

Roland Resel

Kiessig fringes


TALK OUTLINE






500 550 600 650 700 750

Flu

ore

scen

ce (

a.u

.)

Wavelength (nm)

Microspheres



PL

(a

rb.

un

its)

Wavelength (nm)



350 400 450 500 550 600 650 700 750

0,2

0,4

0,6

0,8

1,0

0,2

0,4

0,6

0,8

1,0

Exp

Fit

Wavelength (nm)

Tra

nsm

itta

nce

Exp

Fit

Tra

nsm

itta

nce

POLYMER MULTILAYERS & MICROCAVITIES

SNN

F8BT

10-150 nm

DBR

microcavity

PS:CA


G. Canazza et al. Laser Physics Lett. 11, 035804 (14).


0

20

40

60

80

100

350 400 450 500 550 600 650 700 750

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

Flu

ore

sce

nce

(a

.u.)

SNN

F8BT

FLUORESCENCE OF MICROCAVITIES

Microcavity Quality Factor

(Q)

E=hn, emission energy

DE, FWHM (16 nm)

tc, photon lifetime in the cavity

PS:CA

𝐐 =𝑬

𝜟𝑬= 2𝜋𝜈𝜏𝑐

lexc=405 nm, CW


510 540 570 600 630 660 690

F8

BT

PL

an

d A

SE

(a

.u.)

Wavelength (nm)

350 400 450 500 550 600 650 700 7500

10

20

30

40

50

60

70

80

90

100

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

MICROCAVITY TUNED ON ASE

F8BT

absorption

ASE

Emission

microcavity mode

SNN


550 555 560 565 570 575 580

550 555 560 565 570 575 580

4 nm

Norm

aliz

ed I

nte

nsity

Wavelength (nm)

3 nm

• For very low pumping intensity, the linewidth is very small, indicating an high

optical quality of all-polymer microcavities.

• No apparent evidence of line sharpening is observed for strong pumping.

MICROCAVITY LASING?

550 555 560 565 570 575 580

Wavelength (nm)

Em

issio

n Inte

nsity (

a.u

.)

High pump intensity low pump intensity 150 fs pumping (390 nm)

pump intensity

increase


MICROCAVITY EMISSION: PEAK ASIMMETRY SINGLE GAUSSIAN

FWHM=4.2 nm

TWO GAUSSIANS

FWHM 4.4 nm

FWHM 1.8 nm

550 560 570 580

Inte

nsity (

arb

. units)

Wavelength (nm)

550 560 570 580

Inte

nsity (

arb

. units)

Wavelength (nm)Low pump 1,2 nJ/cm2

(< threshold)

High pump 20 mJ/cm2

( threshold)

150 fs pumping (390 nm)


0 200 400 600 800 1000 1200 1400 1600

Inte

nsity O

UT

(arb

. units)

Pumping Fluence (mJ/cm2)

0

1

2

3

4

5

FW

HM

(nm

)

LASING FROM ALL POLYMER MICROCAVITIES

Laser threshold

• Very low threshold (<20 mJ/cm2).

• Gain switching regime above threshold: avalanche excited state decay

makes faster and faster the emission thus broadening it.

M. Zavelani-Rossi et al. IIT@POLIMI


CONCLUSIONS

• I reported an overview of the work on organic & hybrid photonic

crystals we are performing in Genoa.

• Opals, microsphere monolayer arrays and polymer multilayers are

simple and cheap playgrounds useful to address different photonic

topics like lasing, fluorescence enhancement, hybrid photonic-

plasmonic or photonic-excitonic excitations, switching and sensing.

• I hope this talk could foster your curiosity and stimulate the

study of novel phenomena or technological applications by

using functional polymer/hybrid photonic/plasmonic materials.


ACKNOWLEDGMENTS

Opals & Engineered Colloids

M. Laus, K. Sparnacci & Co.

Università del Piemonte Orientale (AL)

Advanced Optics & Theory

M. Patrini, M. Liscidini, F. Marabelli, L.C. Andreani

Dipartimento di Fisica “A. Volta”, Università di Pavia

Lasing action in all-polymer microcavities

F. Scotognella, M. Zavelani-Rossi, G. Lanzani

IIT@Polimi

Plasmonic Nanostructures @ Opals

F. Buatier de Mongeot & Co.

Dipartimento di Fisica Università di Genova

Hybrid Photonic Crystals

C. Soci, P. Lova

NTU - Singapore

Special Thanks to:

Serena Gazzo

Giovanni Manfredi

Robert J. Knarr

Francesco Campanella

Filippo La Rosa

Marina Alloisio

Rosa Silvia Raggio

Giancarlo Canazza

Simone Congiu

Paola Lova

Luca Occhi

Valentina Robbiano

Marco Pisano

Emanuele Bozzoni

Azo-type Photochromic polymer synthesis

G. Galli et Co.

Università di Pisa

SEM Photonic crystals

L. Boarino & Co.

INRIM - Torino

Materiali Polimerici Nanostrutturati con strutture molecolari e cristalline

mirate, per tecnologie avanzate e per l’ambiente (2010XLLNM3)

X-Ray Reflectance

R. Resel

TU – Graz (A)

Conjugated Polymers @ Opals

F. Cacialli, F. Di Stasio, V. Robbiano

UCL (UK)

Nano Crystals @ Polymer Microcavities

F. Di Stasio, R. Krahne

IIT@Genova

Clathrating Polymers for Photonics

G. Guerra & Co.

Università di Salerno


ADVERTISING EOSAM 2014

Location: Berlin Adlershof, Germany

Duration: 15 - 19 September 2014

TOM 7 – ENERGY HARVESTING AND ORGANIC PHOTONICS

Chair: Guglielmo Lanzani, Istituto Italiano di Tecnologia, (IT)

Co-chairs: David Lidzey, University of Sheffield (GB)

Davide Comoretto, University of Genova (IT)

INVITED SPEAKERS

Jeremy Baumberg, Cambridge University (GB) - PLENARY

Christoph J. Brabec, Friedrich-Alexander University, Erlangen-Nürnberg (DE)

Francesco Buatier de Mongeot, University of Genova (ITA)

Franco Cacialli, University College London (GB)

Fredrik Krebs, Technical University of Denmark (DK)

Gianluca Farinola, University of Bari (IT)

Graham Turnbull, University of St. Andrews (GB)

Jérôme Cornil, Université de Mons (BE)

Jochen Feldmann, Ludwig-Maximilians University Munchen (DE)

Jordi Martorell, Institut de Ciències Fotòniques (ES)

Olle Inganäs, Linköping University (SE)

Roland Resel, Graz University of Technology (AT)

Stephan Kena Cohen, Imperial College (GB)

Documents

ORGANIC & HYBRID PHOTONIC CRYSTALS - unipr.itfilm (Ø 260 nm) • Photons having energy within the PBG cannot propagate into the PhC being backward diffracted. • Dielectric lattice