Photonic Crystals
between Nature and Technology
Roberta De Angelis
Department of Industrial Engineering and INSTM, University of Rome ‘Tor Vergata’
New Materials For Optoelectronics webnemo.uniroma2.it
NeMO Lab
New Materials for Optoelectronics
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Optics
Integrated optics
Optoelectronics
Energy
Sensors
Optical Engineering consultancy
Periodic electromagnetic media
1987
1887
1-D
periodic in
one direction
1-D
2-D
periodic in periodic in
one directiontwo directions
2-D
3-D
periodic in periodic in
three directions
two directions
3-D
periodic in
three directions
Photonic Band Gap
a range of wavelengths where the propagation of light is forbidden
Inverted opals
Greater dielectric contrast than opals
Y. A. Vlasov et al., Nature 414, 289 (2001)
Naturally occurring photonic crystals
Naturally occurring photonic crystals
Precious opal consists of spheres of silicon dioxide molecules
arranged in regular, closely packed planes.
Precious opal consists of spheres of silicon dioxide molecules
arranged in regular, closely packed planes.
Structural color
B. Gralak et al., Opt. Express 9, 567 (2001)
Vukosic et al., Proc. Roy. Soc: Bio. Sci. 266, 1403 (1999)
wing scale
3µm
Wettability
Wettability
Gao, X. Et al. Adv. Mater. 2007, 19 (17), 2213–2217.
Synthesis of a Colloidal Photonic Crystals
1. Gravitational sedimentation
2. Vertical deposition
3. Horizontal deposition
Colloid
Glass substrate
“Foot”
Glass substrate
“Foot”
Glass substrate
Center void
Glass substrate
Q. Yan, Langmuir 2005, 21, 3158-3164
This is what you get
This is what you get
Film
Thicker borders
Void
This is what you get
It is really perfect? Fill factor….
It is really perfect? Cracks….
It is really perfect? Line & Point defects….
We can manage?
• Fill factor
• Cracks
• Line &Point defects
Q. Yan, Langmuir 2005, 21, 3158-3164
Bragg reflection analysis
Light
d(111)
Bragg reflection analysis
max
2
2
2
 2  d111  n  sin   2 
 D  neff  sin 
3
2
eff
2
2
2
2
neff
 1  f   nair
 f  nPMMA
f = 0.74 spheres filling factor (fcc)
2
d111 
D
3
Sphere Diameter
28
Bragg reflection analysis
29
A. Yadav et al. Opt. Mater. , 2013.
Spontaneous emission in a dye doped CPC:
effect of the stop band
30
A. Yadav et al. Opt. Mater. , 2013.
Amplified spontaneous emission
31
A. Yadav et al. Opt. Mater. , 2013.
Optical characterization
Variable angle spectroscopic ellipsometer WVASE32 Woollam
300 nm -1700 nm
-
Refractive index
Thin film Tickness
Transmittance
Reflectance
Flower patterns
2'
10'
15'
20'
27'
30'
35'
37'
R. De Angelis et al. JCIS, 2014.
Flower patterns
Colloid
Glass substrate
“Foot”
Glass substrate
“Foot”
Cracking & Lift-off
Glass substrate
Center void
Glass substrate
M. Naqushabandi et al. Nat. Commun. 2012
D. Brutin Colloids and Surfaces A: Physicochem. Eng. Aspects 2013
R. De Angelis et al. JCIS, 2014
Structural color
Fluorescence
R. De Angelis et al. JCIS, 2014.
Photonic crystal microribbons
50 µm
10 µm
50 µm
10 µm
R. De Angelis et al. JCIS, 2014.
26
Ribbon thickness (m)
Ribbon length (mm)
8
7
6
5
4
3
2
0
50
100 150 200 250 300
Volume (L)
24
22
20
18
16
0
50
100 150 200 250 300
Volume (L)
10 µm
R. De Angelis et al. JCIS, 2014.
Light loss by reflection
n=1.0
n=1.5
BK7 glass
500 nm light
Moth-eye antireflection layers
Credit: Rick Cowen
D.G Stavenga, S Foletti, G Palasantzas, K Arikawa
Proc. R. Soc. B 2006
Optical characterization of coatings
Total transmittance & reflectance measurement set-up
Permanent staff:
Prof. Mauro Casalboni
Prof. Roberto Francini
Dr. Paolo Prosposito
Dr. Fabio De Matteis
Post-doc:
Dr. Roberta De Angelis
Ph.D student:
Dr. Liliana D’Amico