Fujiwara, Takumi

English

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Lehigh University
Lehigh Preserve
US-Japan Winter School Semester Length Glass Courses and Glass Schools
Winter 1-1-2008
Lecture 1, Part 2: Controlling light with nonlinear
optical glasses and plasmonic glasses - Plasmonics
Takumi Fujiwara
Tohoku University, Japan
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Recommended Citation
Fujiwara, Takumi, "Lecture 1, Part 2: Controlling light with nonlinear optical glasses and plasmonic glasses - Plasmonics" (2008). US-
Japan Winter School. 4.
https://preserve.lehigh.edu/imi-tll-courses-usjapanwinterschool/4
Photonic Glass
Takumi FUJIWARA
Tohoku University
Department of Applied Physics
Optical Materials and Sciences Lab.
2008, Jan 7
All-Paid US-Japan Winter School 
on
New Functionalities in Glass
Controlling Light with Nonlinear Optical 
Glasses and Plasmonic Glasses
Outline
1)  Background & Motivation
2)  2nd-order optical nonlinearity in glass
-Controlling light with change of refractive index
3)  Toward real application of electro-
optic glass devices;    
-“UV-poling” and Permanent χ(2)
4)  Recent topics of our research works
-New EO glasses and fiber-type devices
-“Plasmonic Glass”, light localization/propagation
Glass         key material
Motivation
Novel nonlinear “glass materials”
for photonic applications
- High and wide range of transparency
- Good connectivity to glass fiber
- High environmental durability
- Easy shaping to fiber and films
… but not applicable for signal processing 
such as optical switching and modulation etc.
Advanced Photonic Communication
Functional Photonic Devices/Components
with excellent connectivity to the fiber
E/O-Switch, Modulator, Converter, etc
drived by Second-Order Optical Nonlinearity
Second-Order Optical Nonlinearity in Glass
P = ε0 (χ(1) E + χ(2) EE + χ(3) EEE + … )
P : polarization, ε0: dielectric constant, E: electric field of light
2nd-order nonlinearity is NOT allowed 
in glasses with inversion-symmetry
Glass with 2nd-order 
nonlinearity
Permanent connection to 
glass-fibers
2nd-order optical nonlinearity
Photonic Glassglass-crystal
connection
LiNbO3 crystal
Alternative Description of Δn
EO effect (Pockels effect)
Electric field of angular frequency：Ｅ（ω）
Applied electric field：Ｅ（０）
Nonlinear susceptibility：χ(2)
If E(0) > E(ω),   at E=E(0)
P(2) = ΔχE(ω)
where Δχ=2χ(2)E(0) represents an increase in the 
susceptibility proportional to the electric field E(0).
The corresponding incremental change of the 
refractive index is obtained by the relation n2=1+χ, 
to obtain 2nΔn=Δχ, from which
Δn = (χ(2)/n)E(0)
Δn= -rn3E/2 is defined in the Pockels effect, thus,
EO coefficient r is described by
r = - 2χ(2) /n4
EO effect
SHG
Fermat’s Principle： Boundary Refraction
Speed of light：
V＝C0／ｎ
velocity in the medium： V
free space velocity： C0
refractive index： ｎ
large ｎ →V：slow
small ｎ →V：fast
Light rays travel along the path of least time by 
refraction in this case （Snell’ Law: sinθ/sinφ=nL/nS）
small n (fast V )
large n (slow V )
Controlling Light with EO Effect
Change of refractive index (Δn)
Angle of refraction changed by Eappl
Cotrolling light with EO devices
through 2nd order optical nonlinearity
Optical Fiber
Light
EO medium
Electro-Optic Devices
Directional Coupler
2x2 Optical Switch
optical waveguides
electrodes
optical waveguides
NLO substrates
Coupled-mode theory :
“Optical waves in crystals”
A. Yariv and P. Yeh
Advantages of “Photonic Glass”
-Long-term stability 
-Low excess loss 
-Easy to connect
Photonic glass* is the 
best solution for glass-
fiber networks.
*Second-Order Optical 
Nonlinearity
Ｘ
How to induce χ(2) ?
1. Poling with UV/heating 
2. Crystallization
2nd-order nonlinearity induced in glass
YesNostability (no decay)
NoYes (UV)patterning
~1 pm/V~10 pm/Vχ(2) value
CrystallizationPoling
LiNbO3 : ~28 pm/V
Poling in Glass/Fiber
Breaking of inversion symmetry 
in glass
+
_
glass
electrodes
Poling in glass…
Applied electric field
-At elevated temperature
-With UV-laser irradiation
Field-Induced Microstructuring
in Glass Materials
UV-Poling in Glass/Fiber
The Optical Fibre Technology Centre (OFTC)
University of Sydney, Australia 
Thermal Poling
χ(2) was limited by 
<1pm/V
UV-Poling in Ge:SiO2 Fiber
-Larger χ(2) : ~10pm/V
-Periodic structure: χ(2) gratings   
-Degradation      mechanism?
χ(2) EE~ χ(3) EEE
Possible Origin of Induced χ(2)
Orientation of χ(2)
agents
UV-Poling in Ge:SiO2 Glass
-VAD preforms: 15GeO2-85SiO2
-E -field: 0~3x105 V/cm
-UV-laser: 193 nm
Maker-fringe SHG measurementUV-poling in bulk glass
-Quantitative evaluation of SHG
d (χ) coefficients
-Values of d33, d31
-Refractive index: ne, no
Creation of χ(2) in UV-Poled Glass
UV-poling electric field dependences in Ge-doped SiO2
d =(1/2)χ(2)
Decay Behaviors of Induced χ(2)
-χ(2) disappearance 
-single-expo. decay?
Quantitative Analysis of Decay (1)
Absorption Spectra and defects
in Ge-doped SiO2 Glass
Quantitative Analysis of Decay (2)
Deconvolution of Δα
Decay of Δα
χ(2) decay is similar to GeE’ !
Decay Time Constant of Induced χ(2)
Decay time constant of χ(2)
induced in UV-poled glass
~280 days at RT
For long-term 
stability
Hydrogen doping
Comparison of
activation energies
Mechanism of χ(2) Decay
Values of Ea
χ(2) decay and GeE’
~0.4 eV
Dark conductivity
~0.4 eV
Introduction of 
electron scavengers?
Achievement of Stable χ(2)
For 20 years,
>90% performance
application  to 
real field
Origin and Decay of χ(2) in UV-Poled Glass
χ(2) ~ χ(3) Esc
χ(3) susceptibility: increased 
by crystallization
Permanent χ(2) ?
Effective χ(2) through third-order 
nonlinearity
Esc : space-charge field 
caused by defect formation
Ba2TiGe2O8 (BTG)
TiO5 unit
O
Ti
c axis
TiO5 unit
Fresnoite Crystalline Structure
Origin of Ps(spontaneous polarization)
Novel Crystallized Glass－BTG
Surface Crystallization and Orientation
5 μm
Glass
BTG crystalline layer
10 20 30 40 50
2θ / deg.
I
n
t
e
n
s
i
t
y
 
(
a
r
b
.
 
u
n
i
t
s
)
(001) (311)
(002)
THT=750 °C
THT=730 °C
THT=710 °C
THT=700 °C
Stoichiometric composition
c-axis
Benitoite phase
×
×: Benitoite 
phase
2nd-Order Nonlinearity in BTG
YAG
BTG crystallized glass
λ=1064 nm532 nm
-40 -20 0 20 40
0
0.1
0.2
0.3
Angle of incidence / deg.
S
H
 
i
n
t
e
n
s
i
t
y
 
(
a
r
b
.
 
u
n
i
t
)
d =25 pm/V
Maker fringe measurement:
The largest d-value in glass ever reported
Appl. Phys. Lett., 81, 223(2002).
BTG55: 30BaO2-15TiO2-55GeO2
720°C, 3 h
Optical Absorption and Microstructure of 
BTG55 and BTG50
10 μm
10 μm
BTG50
BTG55
Crystalline layer of BTG55 is more dense 
and homogeneous than those of BTG50.
300 400 500 600 700 800
0
20
40
60
80
100
Wavelength / nm
T
r
a
n
s
p
a
r
e
n
c
y
 
/
 
%
BTG50
BTG55
Optical intensity image of Au nano-
particles ordering in glass substrate
J. of Microscopy, 202, (2001) 122
Surface plasmon locallized in  
metal nano-particles
J. R. Krenn (2001)
-electron beam lithography (EBL)
-ITO doped glass substrates with 
electric conductivity for EBL
-gold nano-particles with 100 nm  
diameter and 40 nm height for a 
plasmon resonance wavelength 
of about 630 nm
-plasmon coupling observed by 
photon scanning tunnelling
microscope (PSTM)
200 nm
Plasmonics
Suraface Plasmon (SP)
1. Excitation of SP by photon coupling
a) Kretschmann configuration and b) ray tracing of an Attenuated 
Total Reflection (ATR) setup for coupling surface plasmons. 
In the case, the surface plasmon propagates along the metal/dielectric 
interface.
b)
Suraface Plasmon (SP)
2. Dispersion relationship for SP
metal
Dielectric
(glass)
Wave number of SP： kx
Dielectric constants (relative)：ε1 and ε2
for metal and dielectric, respectively.
kx =
c : speed of light, ω : frequency of the wave
Since ε1 < 0 in metal, for the solution of
kx (plasmon), ε1(ω) < -ε2, below ωsp
Dispersion curve for surface plasmons. At low k, 
the surface plasmon curve (red) approaches the 
photon curve (blue).  
ω
c
ω ε1ε2ε1+ ε2( )
1/2
light
plasmon
non-radiative
Tellurite-based glasses
Photo-Induced Nano-Crystallization by 
UV-Laser Irradiations
・Nano-crystallization by laser heating
・Selective crystallization of metal Te?
・Large nonlinearity: d ~ 30d (LiNbO3)
χ(3) ~ 10χ(3) (Au)
KNbO3-TeO2 glass
Periodic Structure with PM
XeCl excimer
laser（λ=308nm）
Phase Mask (PM)
Laser-Induced Structure Ordering
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
200 400 600 800 1000 1200
Temperature (K)
S
t
a
n
d
a
r
d
 
G
i
b
b
s
 
f
r
e
e
 
e
n
e
r
g
y
 
o
f
f
o
r
m
a
t
i
o
n
 
(
k
J
/
m
o
l
)
TeO2
K2O
Bi2O3
GeO2
BaO
MgO
CaO
SiO2
TiO2
P2O5
B2O3
Al2O3
Nb2O5
Er2O3
S
t
a
n
d
a
r
d
 
G
i
b
b
s
 
f
r
e
e
 
e
n
e
r
g
y
 
o
f
f
o
r
m
a
t
i
o
n
 
(
k
J
/
m
o
l
) KNbO3-TeO2
glass
SEM image
100 nm
ordered structure of 
nano-particles
Periodic Structures of Nano-Particles 2
Structure Ordering in Glass
AFM image (enlarged)
500 nm
-Creation of nano-particles  
with ~100 nm diameter
-Laser intensity dependence 
of nano-particles density
-Te metal confirmed by 
electron diffraction pattern 
TEM Images of Surface Cross-Section
UV-Irradiation
100
201
101
102 202
Metallic Nano-Structures on 
Glass Surface
Plasmonic Glass
Plasmonic Glass for Nano-Circuit
・Metal nano-particles on glass
・Physics for formation
・Design and control of particles
・Nano-photonic circuits
Photo-Induced Nano-Particles Structure
Incident 
photon
Output 
photon
Nano-particles
“Active”-particle
Ordered Nano-Particle Structure
Low Degradation of E-field in 100 nm
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
200 300 400 500 600 700 800
Wavelength (nm)
N
o
r
m
a
l
i
z
e
d
 
E
x
 
(
a
r
b
.
 
u
n
i
t
s
)
Ex (d = 30 nm)
Ex (d = 100 nm)
Ex (d = 300 nm)
E-field：A
E-field：B
Normalized Ex =
A
B
Change of E-field Intensity （ＦＤＴＤ）
SUMMARY
・Developments of new nonlinear optical glasses 
for EO photonic devices
Fiber-Type Devices
for Signal Processing in Optical Communication
・Formation of UV-laser induced metallic nano-
particle structures on glass surface
Plasmonic Glass
for Propagation/Localization of Light
Controlling Light with Nonlinear Optical 
Glasses and Plasmonic Glasses


Lecture 1, Part 2: Controlling light with nonlinear optical glasses and plasmonic glasses - Plasmonics

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Lecture 1, Part 2: Controlling light with nonlinear optical glasses and plasmonic glasses - Plasmonics

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