SAPIEZA Università di Roma
Dipartimento di Energetica
Laboratorio di Fotonica Molecolare
Francesco Michelotti
E-Mail: [email protected]
Tel: +39 – 06 - 49.91.65.62
Workshop Future Trends in Molecular and Bio
Bio--Optoelectronics
Optoelectronics,, Paris,
Paris, December 11th11th-12th 2008
Overview of the activities
A
B
E
C
F
D
G
A) SHG, B) Organic photonics, CD)
Deposition & Processing, E) Organic electro-optics, F) OLEDs, G)
Pico-second nonlinear optics
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Overview of the activities
• Characterisation of photonic devices (wgs, µrings, Bragg, )
• Electro-optic Polymers for photonic active components
• Dye Sensitised Solar Cells and molecular OLED
• Surface electromagnetic waves in metal and dielectric multilayered
structures for biosensors and gas sensors
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Laboratory activities connected to the Workshop
(II)
Photonics based chemical and biological sensors, New generations
of biochips for research and diagnosis, Optical tweezers and new
approaches to light-manipulation of biological objects: micro- and nano-
fluidics
Surface electromagnetic waves in dielectric multilayered structures
and transparent conducting oxides
(III)
(IV)
Molecular and Hybrid photonics
Molecular and Hybrid electronics
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Surface Plasmon Polaritons
• Longitudinal collective excitation of
plasma electrons at a metal/dielectric
interface.
• The effective index of a SPP is larger
than the refractive index of the
dielectric. Therefore they can be
excited only by:
R
TM
Attenuated total reflection (ATR)
Surface roughness (Scattering)
θ
• Widely used in biosensing devices
ΛΛΛΛΛΛΛΛΛ
◊ ◊ ◊◊ ◊ ◊ ◊◊ ◊
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
θ
SEW waves at the boundary of Photonic Crystals
SEW waves at the boundary of Photonic Crystals
Linewidths are smaller than
observed for SPPs
λ=1530nm
TE •
θ
SEW
Kretschman coupling configuration
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SEW waves at the boundary of Photonic Crystals
Application to Biosensing
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
BIOSENSING - a-Si1-xNx :H based 1D Photonic Crystal
L
t=294nm n=1.75 @ λ=1530nm
H
t=240nm n=2.23 @ λ=1530nm
Band Diagram
10 periods
Glass
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
BIOSENSING - a-Si1-xNx :H based 1D Photonic Crystal
2.0
R [ arb.un. ]
1.5
1.0
0.5
λ=1550nm
0
30
40
50
60
70
θ [ deg ]
2.0
R [ arb.un. ]
1.5
1.0
0.5
SPP on Au @ λ=1550 nm
Bare BK7 prism
0
30
40
50
60
θ [ deg ]
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
70
BIOSENSING - a-Si1-xNx :H based 1D Photonic Crystal
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
BIOSENSING - a-Si1-xNx :H Development Stage
θ
θ
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
BIOSENSING - a-Si1-xNx :H based 1D Photonic Crystal
Is it possible to enhance the biosensor
response by introducing further resonances?
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
a-Si1-xNx :H / Polimer 1+1D PC - Gratings fabrication
Tpol=TAMB
hν
488.0 nm
TRANS
CIS
Drift of the
polymer off the
bright regions
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
a-Si1-xNx :H / Polimer 1+1D PC - Gratings fabrication
θ
Lloyd mirror
configuration
λ = 488.0 nm
Glass
I = 60 mW/cm2
Λ= 634 nm
h=118nm
Francesco - Trasparenza sulla fabbricazione dei reticoli di
diffrazione in Disperse Red 1 mediante olografia cis- trans
AFM
∆t = 90 min
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
a-Si1-xNx :H / Polymer 1+1D PC - Dispersion and gap opening
Λ
Glass
Optics Letters 33, 243 (2008)
Optics Express 16(8), 5453 (2008)
Applied Physics Letters 93, 061108 (2008)
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
a-Si1-xNx :H / Polimer 1+2D PC – Hexagonal gratings fabrication
Λ0
Λ0
Λ0
Periodic 2D gratings can be
fabricated by several successive
holographic lithographic steps
Λ1
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
a-Si1-xNx :H / Polymer 1+2D PC - Dispersion and gap opening
2.0
1.5
Λ0
Λ0
λ
GAP
σ= 30 deg
[ µm ]
1.0
σ = 60 deg
σ= 0 deg
0.5
0
2.0 1.5 1.0 0.5 0
0.5
0.5 1.0 1.5 2.0
1.0
Λ1
1.5
2.0
σ [ deg ]
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SEW waves at the boundary of Photonic Crystals
Application to Gas Sensing
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
GAS SENSING - Porous Silicon PC
25 periods
L
t=294nm n=1.75 @ λ=1530nm
H
t=240nm n=2.23 @ λ=1530nm
Porous Silicon layers
p+-Si
Appl.Phys.Lett., 91, 241109 (2007)
FESEM
γ>0
γ<0
θ
Surface mode
Otto coupling configuration
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
•
TE
GAS SENSING - Porous Silicon PC – SEW dispersion
Measured
Theoretical
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
GAS SENSING - Porous Silicon PC – Ethanol vapour
Organic vapours sensor based on:
•
θ
TE
Extremely large effective area of the
porous silicon photonic crystal
SEW mode
ATR - Otto coupling
IN
OUT
Very narrow resonance dips
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
GAS SENSING - Porous Silicon PC – Porous Silicon PC– Ethanol
SEW Mode
TE Mode
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
GAS SENSING - Porous Silicon PC – Ethanol vs Methanol
M ethanol ≅ 7.67 ⋅10−26 kg
nethanol = 1 .36
M methanol ≅ 5.3 ⋅10−26 kg
n methanol = 1 .33
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SPP in TCO – Literature and results
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SPP in TCO – Literature and results
40 deg
70 deg
2.38 µm
~ 1.18 µm
1.00 µm
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Indium Tin Oxide (ITO) – Single films – SPR dispersion
TM
θ
• Resonances observed
• Respect to the sharp
ones observed in Au,
they are as large as
almost all the angular
window (because closer
to the plasma frequency)
77 nm
134 nm
36Ω/□
13Ω/□
104 nm
17Ω/□
• They could greatly affect
the NIR emission pattern
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
194 nm
Indium Tin Oxide (ITO) – Single films – SPR dispersion
77 nm
134 nm
77 nm
134 nm
104 nm
194 nm
104 nm
194 nm
Measurements
Analytical Calculation
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Indium Tin Oxide (ITO) – Single films – SPR dispersion
In the case of ITO:
1) The plasma edge is red
shifted up to the IR due to
lower carrier concentration
and different effective mass
2) The skin depth is larger than
for metals
3) Coupled SPP are moke likely to apper also for relatively
large film thicknesses
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SPP just begin to be an issue in Organic Solar Cells too
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SPP just begin to be an issue in Organic Solar Cells too
Link to
(IV) Molecular and Hybrid electronics
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
SPP and efficiency of IR harvesting DSSC
• In a DSSC the TCO (ITO but also others)
layer can support SP in the IR range with
dispersion depending on the properties of
the dielectric layers at the interfaces.
TCO
TiO2
SUB
Sol
Pt
SUB
• Periodic corrugations and/or simply the
roughness of the TiO2 layer can scatter
light in the dye sensitised solution C.
• C. but they are also likely to couple to the
SP modes whose acceptance angle is
very large with an increase of the effective
optical thickness of the sensitised cell.
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare
Thank you for your kind attention
100 nm
SAPIEZA Università di Roma - Laboratorio di Fotonica Molecolare