Australian – Japanese Students workshop on Nanophtonics(Student Exchange Support Program by Shizuoka University)

Professor Saulius Juodkazis’s group
Center for Micro Photonics
Swinburne University of Technology, Melbourne, Australia
Professor Atsushi Sugita’s group
Department of Materials Science
Shizuoka University, Japan.
November 16-23, 2012
Swinburne University of Technology, Melbourne, Australia

1Preface
On behalf of the members of Shizuoka University, I would like to thank Professor Saulius Juodkazis
to give us the opportunity to visit the laboratory and to organizing the symposiums. And we are
grateful for all the members of Center for Micro Photonics in Swinburne University of technology
for sharing the special times with us. We also appreciate Professor Vygantas Mizeikis and Dr.
Atsushi Ono for their help of arranging the program.
I begin by introducing the SSSV program organized by our institute and the backgrounds. The aimof the program stimulates our undergraduate and graduate students by exchanging the discussions
with the young researches of the same generations. The program has two options; in first options,
we visit the institute in the foreign countries and hold the symposium for discussions about theirresearches. In the second, we invite the students in the foreign countries and hold the symposium.
This is the second year of the program and ten groups participate in the programs.
As you know, Japan is surrounded by the ocean. Most of the Japanese people do not have any
experiences of interactions with the foreign countries and foreign peoples. It is a big adventure forthem to visit the foreign countries and make conversations with non-native languages. Until about
20 years ago, the Japanese economy was booming, because of the good cycles between the domestic
consumptions and productions. Most of the Japanese people do not have to contact directly with theforeign peoples. At the edge of the 21st century, the Japanese economy is turndown and most of
production companies are expanding their production base worldwide. It is unavoidable for most of
the Japanese engineers to do their business with the engineer in the foreign countries, especiallyAsia. Off course, even if our students visit Australia for one week, it is not sufficient to learn whatlooks like the foreign countries and the foreign people. Their experiences in Melbourne are the great
step for them to grow up the independent engineer in the future.
Off course, the symposium is one of the most important events in the program. Our group makes a
lot of effort for producing thin film optical materials, especially thin film nonlinear optical materials.
These materials are not always our original ones, but we may create new technologies byassembling them with other optics or optronics technologies. We give great attentions to theirapplications to the fields of the nanotechonologies and nanosciences. Professor Juodkazis’s group is
the one of the most prominent laboratories in the field of the nanophotonics. We believe that newtechnologies such as nonlinear optics for nanophotonics will be born by combining the knowledge
and skills accumulated by the two groups.
Finally, we are grateful if the program are fruitful for all the participants of the two groups.
Professor Atsushi Sugita
2

Shizuoka-Swinburne Workshop on fast & small (fs)
Swinburne University of Technology
19 November 2012
Room ATC 205 (Advanced Technologies Centre)

Time

Presenter

Title

10.00 – 10.15

Coffee/tea

Welcome10.15 – 10.30

Prof. Atsushi Sugita

Research activity about nonlinear optics and femtosecond

Shizuoka University, Japan

spectroscopy

Mr. Yasuaki Sato

Second order Nonlinear optics of

Shizuoka University, Japan

host-guest type polymers

Mr. Kazuma Ito

Development of new nonlinear optical

Shizuoka University, Japannear-infrared frequency regions

Mr. Yoshihiro Ono

SecondShizuoka University, Japanpolymers pumped by surface plasmons excited by

10.30 – 10.45
10.45 – 11.00
11.00 – 11.15

harmonic

generations

on electrically poledofchromophores for
Nonlinear

opticalKretchmann configurations.
11.15 – 11.30

Mr. Masashi Kamiya

Development of luminescence thin films for

Shizuoka University, Japan

Electron-excitation assisted optical

11.30 – 11.45

Coffee/tea

11.45 – 12.00

Ms. Jennifer Hartley

microscopes

Optical fiber SERS probe for biochemical sensing

Swinburne University
12.00 – 12.15
12.15 - 12.30

Ms. Zubaidah Ningsih

The Temporal Co-stimulation of NGF and EGF EffectSwinburne University

Toward the Kinetics of Cell Signal Transduction Pathways

Mr. Jonathan Tollerud

Ultrafast

Swinburne University

Many-Body Effects in Semiconductor Nanostructures

Multidimensional

SpectroscopytoRevealCoherent Dynamics in Photosynthetic Light-Harvesting
12.30 – 13.30

Lunch at ATC 205

13.30 – 13.40

Mr.

13.40 – 13.50

Mr. Alireza Lajevardipour

Lab tour: fluorescence lifetime imaging microscopy

13.50 – 14.00

Mr. Gethin Richards

Lab tour: ultra-fast spectroscopy

14.00 – 14.30

Mr. Gediminas Gervinskas

Lab tour: nano-lab

Ričardas Buividas

Lab tour: femto-laser microfabrication

Mr. Gediminas Seniutinas
14.30 – 15.00

End3About Shizuoka University and Shizuoka prefecture
Here, we introduce Shizuoka University and Shizuoka prefecture. The Japan has 47 local
governments and at least one national university is established in each prefecture. Our Shizuoka
University is located in Shizuoka prefecture. The population of Shizuoka prefecture isapproximately 3,700,000 in 2012 and it is the tenth most populated in 47 prefectures. The mostimportant industry is the production of transportation machineries, such as automobiles and motor
cycles. Yamaha Motor Company and Suzuki Motor Corporations, famous for their motor cycles,
have their headquarters in Shizuoka. The founders of Toyota Motor Corporation and Honda Motor
Company were born and began their businesses in Shizuoka. Before World War II, cotton textile
industry used to be one of the major industries in Japan. Toyota, Yamaha, and Suzuki started fromsupplying weaving machines. Hamamatsu Photonics K. K., famous for their Photomultiplier tubes,
has the headquarter in Hamamatsu city. The origin of the name is clearly the name of the city, thesecond biggest city in Shizuoka Prefectures.
Now, Shizuoka University has 6 faculties, and approximately 8,800 undergraduate students and1,500 graduate students study their academics under the instructions of 1,100 university staffs.
There are two campuses at Shizuoka cities and Hamamatsu cities. Our team belongs to Faculty ofEngineering in Hamamatsu campus.
Shizuoka University was inaugurated on June 1, 1949, following approval on May 31 of the same
year for the university's establishment through the unification of five educational institutions: theformer Shizuoka High School, Shizuoka Normal School and Shizuoka 2nd Normal School ,Shizuoka Normal School for Youth and Hamamatsu College of Technology.
Subsequently, the university absorbed Shizuoka Prefectural College of Agriculture , moved to its
present Shizuoka and Hamamatsu Campuses, and by undertaking the reorganization andenlargement of its faculties and other educational departments, assumed its present form. In theyears to come, the university will continue to make efforts to upgrade and enrich its structure.
The roots of the Faculty of Engineering date back to 1922 and the founding of Hamamatsu
Technical High School. With the ideal of "Freedom and Enlightenment, Creation for the Future,"
the Faculty has trained numerous pioneering researchers and technologists. Hamamatsu City,
where the campus is located, has a rich tradition of innovation and was a gathering place fortechnologists from throughout Japan during the Edo era. Today, the city retains a spirit ofcraftsmanship, with many enterprises possessing unique technologies and products. In tune withthis environment, the Faculty of Engineering hosts a variety of enterprise-supported courses.
Through such efforts as Creative Educational Training, in which students gain experience in robot
construction from their first year, the Faculty conveys the pleasure of hands-on fabrication, andmany go on to the Graduate School of Engineering's Doctoral Program.
4

Introductions of Dr. Sugita laboratory in Shizuoka University
Educational Background of Professor Atsushi Sugita
Professor Atsushi Sugita received B.A. degree in 1994, Master degree in 1996 and Ph. D degreein 1999 from Tokyo University. He studied ultrafast dynamics of solid-state semiconducting
materials with femtosecond time-resolved spectroscopies. He also tried building the opticalparametric amplifier systems covering the near-IR and mid-IR wavelengths. He joined thedepartment of Materials Sciences in Shizuoka University as a research associated in 2001. He
joined the attosecond science team in Max-Plank Institute for Quantum Optics in Germany as avisiting researcher for a year in 2005. Professor Ferencz Krausz, the coordinator of the team, is apioneer of the attosecond sciences and he is also famous as one of the founders of the Femtolasers
GmbH. Professor Sugita built high power mode-locked oscillator based on Yb:YAG thin disk laser.
He established his independent laboratory in 2007. In 2012, ten members, five undergraduate
students and five Master course students join his laboratory. 24 alumni have graduated from hislaboratory.
Current Research Projects
Our group joins the divisions of the polymer science and engineering. We play a part ofexamining surface and interface properties of polymeric materials using spectroscopic techniques.
The surface properties of the polymers have been studied for long decades. The phenomena areclosely associated with the adhesion phenomena between the two materials. However, we do not
fully understand the phenomena, even though a lot of efforts have been made. It is probably
because the polymer can take several conformations and they exhibit complex structures dependingon their surrounding environments.
Professor Sugita has a lot of experiences of operating femtosecond lasers. Taking advantage ofthe novel light sources, we study vigorously about surface alignment effects and the subsequent
nonlinear optics. The researches include not only examining the physical properties of the polymer
surface but also preparing the materials exhibiting excellent optical behaviors in the surface.
Recently, we try building the new technologies by combining the surface nonlinear optics withsurface plasmonics.
Research Topics
Surface Nonlinear Optics of Polymer Materials
In the project, we examine the methods nonelectrically poling polymer nonlinear opticalmaterials for second order nonlinear optical susceptibilities. The polymer optical materials haveattracted great interests because of their unique properties such as light weightiness, low
production cost and easiness in fabrications. The investigation about the nonlinear optical (NLO)
polymers is one of the most important issues in the fields, and a lot of unique NLO polymers havebeen ever designed and developed until now.
5

When we operate the NLO polymers for the second order nonlinear optics, we have to conduct
so-called poling procedures. The procedure includes the process of applying electric fields as high asa few kV/mm in the materials. Dielectric break down occurs frequently and it is difficult to prepare
the materials with wide areas and large volumes. We have developed a series of polar polymers
which unique behaviors of self-organizing polar conformations. Taking advantage of thepolarization

self-organization

effects,

wesuccessfully

obtainedsecondorder

nonlinearsusceptibilities without conventional poling procedures. We continue to seek the optimized
conditions for obtaining larger nonlinearities with nonelectrical methods.
Nonlinear Optics for Plasmonics
In the project, we make investigations about nonlinear optical interactions between surface
plasmon and nonlinear polymers. As you know, nonlinear optics is one of the most fundamental
element technologies in the fields of current optics and optronics. The challenge of developing
nonlinear optical devices for nanophotonics and plasmonice is one of the most important issues forfurther progress of these fields. The nonlinearities of the metallic materials, where the surface
plasmon are created, are generally small because of their conductivities. In order to overcome theproblems, we propose to enhance the nonlinearities of the metal surface by fabricating thenonlinear optical polymers developed in our previous studies.
As a first step, we succeeded in observing the intense second harmonic signals from the NLO
polymers excited by surface plasmon enhanced optical fields induced with attenuated totalreflection methods. We are now making examinations about the nonlinear optical interactions
between the polymers and localized surface plasmons in metal nanoparticles.
Synthesis of Nonlinear Optical Chromophores for Near-IR Operations.
Fundamental structures of nonlinear optical polymers consist of host – guest complex structures.
The guest chromophores play a role of nonlinear light-matter interactions, while the host polymers
fix the positions of the guest chromophores. Depending on the molecular designs, we can control thenonlinearities and resonance frequencies of the chromophores. Recently, the synthesis ofchromophores for near-infrared operations has advanced considerably. These novel chromophores
are attractive for applications to fast optical telecommunication systems. These materials are also
useful for improving our thin film nonlinear optical polymer technologies and developing thenonlinear optical devices for the plasmonics. We are now preparing the novel chromophores
systematically with different resonance wavelengths from 400 and 800nm.
Developing Inorganic nonlinear optical thin films
Our institute has long traditions of crystal growth technologies for semiconducting materials.
With the aids of these groups, we begin developing the nonlinear optical inorganic thin films. In
general, the inorganic nonlinear optical materials are robust and their damage thresholds and6nonlinearities are much higher than the NLO polymers. We begin by preparing thin films of
AgGaS2, the materials known as the novel NLO materials for mid-IR operations. In the future, wewould like to build the NLO photonic crystals or waveguides based on these materials.

7

Second-Order Nonlinear Optical Susceptibility of host-guest type polymers containing TCF-based
guest chromophore
Shizuoka University, Department of Material Science
Kazuma Ito, Yasuaki Sato, Wataru Inami, Nobuyuki Mase, Kawata Yoshimasa, Atsushi Sugita.
Introduction
Nonlinear optics (NLO) has been studied for almost half a century since P. A. Franken firstsucceeded in observing second harmonic generation (SHG) in 1961. Recent progress of stable andhigh power light emitting diode technologies promoted solid-state laser and fiber laser technologies
in near-infrared regions. Furthermore, the LED pumped ultrafast oscillators and amplifiers arealso reported. A lot of researchers propose and examine the applications of these advanced lightsources especially in the fields of high density and fast telecommunication systems, biomedical
imaging and mechanical machining. The nonlinear optics and their applications are one of the mostfundamental technologies that are made up of the current optics and optronics. Hence, it isimportant to develop NLO materials operating in the near-infrared regions so as to satisfy thedemands.
The NLO materials are typically classified into three groups, that is, inorganic crystalline
materials, organic crystalline materials and polymeric materials. Even though the first two classes
are in practical use, the NLO polymers still attract great interests because of their flexibility,
easiness in fabrication and low production cost. The fundamental structures of the NLO polymers
are typically consisted of host-guest complex materials. The guest chromophores play a role ofnonlinear light-matter interactions, while the host materials fix the positions of the chromophores.
Until now, a lot of host polymer materials, such as poly (methyl methacrylate), poly carbonate andpoly styrene have been developed. Most of the efforts seem to be mode to develop the guest
chromophore with large molecular hyperpolarizabilities.
As for molecular designs of the guest chromophore, most of the popular NLO chromophores
consist of π-conjugated system sandwiched between electron donoting and electron accepting
moieties. By combining the moieties with appropriated design, we may prepare the chromophores
at specific operating light frequencies. Recently, there are several reports about the novel NLO
chromophores for near-IR operations2, 3. These chromophores are mostly used for the applications
to the 3rd order nonlinear optics. However, supposed that we manage to orderly orient thesechromophores in host materials, the materials will be useful for the 2nd order nonlinear optics.
In

thepresent,

among

several

NLO

chromophoresfornear-IRfrequencies,

2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydroofuran (TCF), one of most promising NLO
chromophore for the near-IR operations were synthesized and studied as the guest materials for the
2nd order nonlinear optics. The TCF chromophores are unique in that they have TCF acceptors
with highly electron withdrawing abilities.
First, the synthesis of the TCF chromophores is reported. Second, the 2nd order nonlinear
8

optical susceptibility of the polymers with the TCF chromophores as the guest is addressed. In thelast part of the presentation, we will report the strategy of developing the chromophore with longer
conjugation lengths and the progress of synthesis.
Experiments

Scheme 1. Synthesis of TCF acceptor and TCF chromophore
The TCF chromophore (5) was synthesized with the two steps shown in Scheme 1. At First step,
TCF acceptor (3) was carried out with 5-hydroxy-3-trimethyl-butan-2-one (1) and malononitrile (2).
At the second step, the material (4) with the electron donoting moieties was added to TCF acceptor(3), which results in the productions of the molecule (5).
The samples for measuring several optical properties were the host-guest materials consisting of
the molecule 5 as the guest and polymethyl methacrylate (PMMA) as the host. The thin film of thehost-guest polymers were fabricated on

β：241×10-30 esu

β：54×10-30 esu

the glass substrate with the spin coating
method. The film thickness of the films
was 100 nm. The linear and nonlinear
optical properties were characterized

Figure 1. Structure and hyperpolarizability of TCF

with a UV-VIS absorption spectroscopy

cromophore and DR1.

and a second harmonic spectroscopy.
The materials should have noncentro-symmetric structures for the second-order NLO
susceptibilities. In as prepared conditions, the host-guest polymers have the centro-symmetricstructures because the guest chromophores are randomly oriented in the host polymers. In general,so called poling procedure is conducted to align the chromophores in polar order. In the present, we
tried aligning the NLO chromophores in the polar order with nonelectrical poling method proposedin our previous study. In the methods, the driving forces of alignments are the surface orientation
effects and the orientation polarization effects with the internal field due to the surface energy
difference between the electrodes sandwiching the polymers. As a reference, the materials with
Disperse Red 1(Figure 1), one of the most popular NLO chromophores was measured under the9

same conditions. The excitation light sources for the second harmonic method is femtosecond opticalpulses from the Ti:sapphire regenerative amplifier. The center wavelength, the pulse energy andthe pulse width were 800 nm, 1mJ and 150 fs, respectively.
Results and Discussion
Figure 2 shows the linear absorption spectrum of the1

PMMA doped with the TCF and DR1chromophores. The
Absorbance [-]TCF

absorption peak and edge of the materials with the TCF
chromophore were 588 nm, and 660 nm, respectively,
while those of the materials with DR1 were 506 nm and

DR1

0.8
0.6
0.4
0.2

595 nm, respectively. Both of the absorption peak and0edge wavelengths of the former were much longer than

400of the latter. Hence, the former materials are more

500

600

700

Wavelength [nm]

800

900

Figure 2. Absorption spectram of DR1 andsuitable than the latter materials as the guest

TCF

chromophore for near-IR operations in term of theresonance conditions. Figure 3 show the SH signaloftheexcitation

lights.

Here,

the

p-polarizedcomponents of the SH lights was recorded. The similar

SHG Intensity [a.u.]

intensities as a function of the polarization angles γpDR1(実測値)
DR1(理論値)
TCF(実測値)
TCF(理論値)

600

400

200

pump light polarization dependence were reported in
the case of the the poled polymer and self-assembled

0
0

30

60

90

120

150

180

Incident angle [ °]monolayer in the previous studies. Assuming that theorientation of NLO chromophores belong to C ∞ v Figure 3. SHG intensity of the dependence of thesymmetry, there are only three nonzero second-order nonlinear optical susceptibilities components,zzz, zii, and izi. Using these nonzero tensor components, the SH light intensity is expressed as.



 



I SH  p  K  cos 2  p   A   zzz  B   izi   C  cos 2  p  D  sin 2  p   zii

2(1)

A, B, C, D and K are the parameters related to the refractive index, frequencies at thefundamental and SH lights. The details are seen in Ref. 4.
The

present

pump

beam

polarization

Table 1. Various parameters of DR1 and TCF

dependence results in this study were well

Nonlinear

reproduced with Eq. (1). In Table 1, orientation

coefficientorder parameter P2 as well as the nonlinear
coefficients is summarized. The absolute value ofthe nonlinear coefficient was determined bycomparing the SHG signals from the z-cut quartz

Order parameterd [pm/V]P2 [-]

DR1

0.71

0.82

TCF

1.42

0.84

substrates studied with the same geometries. The order parameter P2 was related to the ratiozzz/zii as shown in Ref. 4. The nonlinear coefficient of TCF chromophore doped PMMA was almost
10

as twice as that of the DR1 doped PMMA. Since the order parameter P2 of the former is almost thesame as that of the latter, the difference in the nonlinear coefficients is attributed to the differencein the molecular hyperpolarizabilities between these two NLO chromophores.
Future Scope
π-Conjugation System

The peak absorption wavwlength of thechromophores is approximately 800 nm. The

Long Carbon Chain
High Solubility

wavelength is important in the field of theThiophene Linker

femtosecond technologies, because it matches tothe oscillation wavelengths of mode locked Ti:

TCF-CF3 Acceptor

sapphire lasers, one of the most popular
femtosecond optical light sources.

Figure 4 dvanced NLO chromophore design

We start developing the new NLO chromophore 23 with larger nonlinearities in the near-IR
reagions (Scheme 2). The following two points are taken into accounts to meet the demands. First,
the NLO chromophore 23 has TCF-CF3 moiety as the electron acceptors with higher
electron-withdrawing abilities than the TCF moiety. Second, the π-conjugation length is much
longer than that of TCF chromophore 5 for red-shifting the resonance wavelengths.
It should be noticed that the π-conjugated moiety and the acceptor moiety are linked with athiophene so as to extend π-conjugation length. It is because of improving the stabilities. In order to
OH
F
+

N
H

CHO

3 steps

S

S

Br

C6H13

Br
11

O
F3C

C6H13

S
Br
C6H13

THF (5.0 M)
0oC, 24 h

15

MeMgI(2.5 eq)

OH
NC

10

S
P+Bu3BrC6H13

C6H13
14

CN

O

LiOEt (0.1 eq)
OH + NC
CF3

CF3 THF (1.0 M)
0oC, 12 h
16

N
CHO

PBu3

C6H13

2) HCl aq

913

12 (y. 6%)
TMSCN (1.1 eq)
KCN (0.1 eq)
18-crown-6 (0.01 eq)

P+Bu3Br-O

CHO
8 (y. 80%)

PBr3

OH

1) LiOEtO+NDMSO (1.5 M)
120oC, 60 h

7 (3.0 eq)

6OH

OH K2CO3 (1.5 eq)

17

CN

CN
THF (1.0 M)
60oC, 24 h

F3C

O
CN
19 (7 %)

18 (2.5 eq)

OH
OH

OH

10 + 14

LiOEt

POCl3
DMF

N

N

N

C6H13

C6H13

C6H13

17
LiOEt

C6H13

S

C6H13

C6H13

S

S

CN
CHO

F3C

O

CN
CN

20

21

Scheme 2. Synthesis of advanced NLO chromophore.
1123

inducing noncentro-symmetric structures with the poling procedures, the annealing procedures at
the high temperatures are unavoidable. Hence, it is ideal for the chromophores to have highthermal decomposition temperatures. So the NLO chromophores having a maximum absorption
wavelength in the vicinity of the near infrared have been developed by extending the π-conjugation
length while maintaining high thermal stability by introducing a thiophene at the site of
π-conjugation. The solubility of the chromophore is poor because they have polar structure. In orderto improve the solubility of the chromophores, the long alkyl side chains are introduced
π-Conjugation System
Long Carbon Chain
High Solubility
Thiophene Linker
TCF-CF3 Acceptor(
Figure 4).
The synthesis proceeds by dividing into three routes. The first route is the production of
π-conjugated system bondedwith electron donating moieties 10. The second route is the synthesis ofdue thiophene linker 14. The third route is the production of TCF-CF3 acceptors. In the present
stage, the products 8, 12, 19 are successfully obtained. We will build to the products 10, 14, and 19
and combine them to build the final product 23 in the near future.
References
1.

P. A. Franken, et al, Phys. Rev. Lett. 1961, 7 (4), 118.

2.

H. He, et al, Chem. Mater. 2002, 14 (5), 2393.

3.

J. Pérez-Moreno, et al, J. Am. Chem. Soc. 2009, 131 (14), 5084.

4.

K. Kajikawa, et al, Jpn. J. Appl. Phys. 1991, 30 (5), 1050.

12

Second-order nonlinear optical susceptibility of nonelectrically poled host-guest type polymers
Shizuoka University. Department of Material Science
Yasuaki Sato, Yasuaki Tamaki, Kenta Murakami, Kazuma Ito, Wataru Inami, Nobuyuki Mase,
Yoshimasa Kawata, Atsushi Sugita.
Introduction
Nonlinear optical (NLO) polymers have been studied for long decades, because of their uniqueproperties such as lightweightness, low production costs and easiness in fabrications. Taking
advantage of those unique properties, these materials are indispensable for building all plastic
optics or optronics. The fundamental structures of NLO polymers consist of complexes between thehost and guest materials. The nonlinear light-matter interactions occur in the guest chromophores,
while the host polymers fix the position of the guest materials. Basic configuration of guest
chromophores often have so-called push-pull structures, in which π-conjugated systems are
sandwiched between electron-donating and electron-accepting moieties. These materials exhibit
large nonlinearity, when they are operated by the light waves with near-resonance frequencies.
Even though a lot of novel NLO chromophores have been developed, a lot of efforts still have been
made to design and synthesize new chromophores.
Recently, several NLO chromophores were developed suitable for the operation in the near-IR
regions. These new chromophores seem to meet demand for the applications in fast
telecommunication systems. Especially, the NLO chromophores with tricyano furan moieties attract
great interests because of its large nonlinearity in the near-infrared regions. Most of the previous
studies paid attentions to their third order nonlinearity for fast optical modulator and opticalswitching systems. Supposed that they were oriented in the polar configurations, the polymers with
the TCF chromophores are promising as second order nonlinear optical materials for the operationsin the near-infrared regions.
In as-prepared conditions, the NLO polymers do not exhibit second-order nonlinear opticalsusceptibility for the wavelength conversions. It is because the NLO choromophores are distributed
randomly and the materials have symmetric structure. In order to break the centro-symmetry,so-called polling procedures are conducted. In theconventional poling procedure, the DC electric fields ashigh as 100 kV/mm are applied inside the materials at
the temperature above the glass transition points (Tg).
During the poling procedure, the dielectric breakdown
occurs frequently and it is quite difficult to prepare thesecond-order NLO susceptibilities in large volume andwide areas. In our previous study, noncentro-symmetricstructures were successfully induced in NLO polymers
with nonelectrical poling method. All we had to do was to
13

Figure 1.

Triciano furan (TCF)

chromophore was investigated inpresent study.

sandwich the polymeric materials between the electrodes with different surface energies and toanneal at the temperatures higher than the glass transition points. We demonstrated thenonelectrical poling effects in the materials with the Disperse Red 1 (DR1), one of the most popular
NLO chromophores. The nonelectrical poling method is universally applicable for the materials
other than the systems with the DR1.
In present study, we will report the second-order nonlinear optical properties of host-guest
polymers with TCF chromophores as a guest. The polar ordering of the chromophores were obtainedwith the nonelectrical poling effects proposed in our previous study. Our experimental results
proved the second harmonic conversion efficiency was approximately two times higher than thatwith DR1 at 800 nm.
Experiment
The TCF chromophore was synthesized with themethod reported in previous studies. Poly (methyl
methacrylate) (PMMA), one of the most popular hostmaterials for the NLO polymers was selected. The
concentration of the chromophores in the nonlinear
optical material was 10 wt%. The NLO polymers were
coated on the glass substrates with spin coating
methods. The films with the thickness between 100 nm
and 2 μm were prepared. The DR1 doped PMMA wasalso prepared as a reference. The nonelectrical polingprocedure

reportedinourprevious

study

was

Figure 2 Linear absorption spectrumof TCF chromophores and DR1 doped
PMMA

conducted to induce the non-centrosymmetry in the materials.
The second order nonlinear optical susceptibility was characterized with the second harmonic
methods. The light source was optical pulses emitted from a Ti: sapphire regenerative amplifier.
The wavelength, the pulse energy, and the pulse width were 800 nm, 1 mJ, and 150 fs, respectively
at 1 kHz-repetition frequencies. The polarization of the excitation light is controlled with a halfwave plate, and the polarization of the SH lights was resolved by Glan-Tellar prism. The SH lights
was detected by a photomultiplier tube after separating from unconverted fundamental components
with color glass filters.
Result and discussion
Figure 2 shows linear absorption spectrum of the TCF chromophores doped films as well as theDR1 doped PMMA films. The absorption peak of the TCF chromophores doped PMMA was λmax =558 nm, while that of the DR1 doped PMMA was λmax = 494 nm. The former was 60 nm longer
than the latter. Since the conjugation lengths of those two chromophores were almost comparable,
the difference in the resonance conditions is likely due to the difference in the degree of the electron
14

acceptances between these two materials.
Figure 3 shows the SH signals intensity fromthe TCF chromophores doped PMMA's. The
measurements were conducted during a heating
andsubsequentcooling

procedureatthetemperatures between 40 and 150 ℃ . The
temperature changing rate was 3℃/ min. In the
as-prepared conditions, the sample did not exhibit
almost any SH signals. In the heating steps, thesamples

emittedtheSHsignalsatthetemperature higher than 100 ℃ . The glasstransition point of the PMMA was approximately
100 ℃. It is concluded that the re-distributional

Figure 3.
emits

Temperature dependence of theSHG

intensity

of

the

TCF

chromophores doped in PMMA

motions of the polymer chain segments promoted forming the non centro-symmetric structures in
the host materials. The polar order of the NLO chromophores are likely accompanied by thepolarization formations of the host polymers. Once the non centro-symmetric structures in the NLO
polymers are formed, they existed stably. Oncethe noncentrosymmetric structures in the NLO
polymers are formed, they existed stably andremained even after cooling the materials below

Tg. The present experimental results indicatedthat

nonelectricalpolingproceduresaresuitable for the NLO polymer systems with new
TCF chromophores as a guest.
Figure 4 shows the p- and s-polarized SH
signalintensitiesasafunctionofFigure 4.

Excitation light polarization

thedependence of the SH signal intensities

polarization angles γp of the excitation lights.

emitted from the TCF chromophores doped

Here, the thickness of the sample was 700 nm,

PMMA.

and it was annealed at 140 ℃. The curves were quite similar to those of poled polymer andself-assembled monolayers (SAM) in the Langmuir-Blodgett films. In the poled polymer and theSAM, the orientational order of the NLO chromophores is expressed with C∞v symmetry (Figure 5).
The chromophores are slightly tilted against the normal of the substrate, while they are distributed
randomly in the plane of the substrate surface. In the symmetry, there are only three non-zeromacroscopic nonlinear optical susceptibility components as zzz, zii、and izi (i=x or y). Assumingthat  is the predominant tensor component the molecular hyperpolarizability, the macroscopic
nonlinear optical susceptibility components are expressed as Eq. (1) - (3).

 zzz  N s  L z 2   L2z    cos 3    (1)15

 zii 1
N s  L z 2   L2i    cos   sin 2    2(2)

 izi 1
N s  Li 2   L z    Li   cos   sin 2    
2(3)

Here,  is the molecular long axis and  is the average molecular tilt angle. Ns is the density of thechromophores, and Li() represents the local field factor in the direction at the i frequency ω. Using
these tensor components, the p- and s-polarized SH are expressed with Eq. (4) and (5).









I SH  p ,  a  0  K  cos 2  p   A   zzz  B   izi   C  cos 2  p  D  sin 2  p   zii

2

(4)

2


I SH   p ,  a    K  E  sin  p cos  p   yzy
2


(5)

Here, A, B, C, D, E, and K is the parameter related to the incident angle of the pump beam, andthe refractive index of the fundamental and SH light waves. The present experimental results werereproduced well with the model expressed with Eq. (4) and (5). The average molecular tilt angle  isrelated to the ratio of the nonlinear susceptibility tensor components as zzz/zii as Eq. (6) and (7).
tan 2  

P2   2
 zzz /  zii(6)

3 cos 2   1(7)

2

Using the fitted values of zzz/zii, the averagemolecular

tilt

angle

and

order

parameteraredetermined as  =17.7° and P2() = 0.862.
Figure 6 shows the film thickness dependence of
nonlinear coefficient of TCF chromophores and DR1
doped PMMA. The absolute value of the nonlinear
coefficient deff was determined by comparing with thedata of the z-cut quartz plate measured at the same
spectroscopic geometry. The nonlinear coefficients of1

film thickness becomes thicker. The nonlinearity of

0.8

the materials with the TCF chromopores is greaterthan that of DR1 doped PMMA. On the other hand,the order parameter of the TCF chromophores doped
thin film was almost the same as that of DR1 doped
the thin film. This result would indicate that TCF
choromophores have resonance condition is closer tothe excitation light and nonlinearity of chromophores
itself is large.

Order parameterthe both the materials decrease monotonously as the

0.6
DR1
0.4

TCF

0.2
0
0

500

1000

1500

2000

Film thickness [nm]Figure 6.

Nonlinear coefficients (a)and order parameter (b) of the TCF
chromophores doped and DR1 doped
PMMA as a function of film thickness.

16Conclusion
In the study, the second-order nonlinear optical susceptibility of the TCF chromophores doped in
the PMMA was reported. The material exhibited the second-order nonlinear optical susceptibility
simply by annealing at a temperature higher than Tg. The nonlinearity of the materials was twiceas large as that of the DR1 doped PMMA at the operating wavelength of 800 nm. The materials arepromising as the second-order nonlinear optical materials for all-plastic optronics in thenear-infrared operations.
Reference
1.

Javier Perez-Moreno et al, J. AM. CHEM. SOC. 131 (14), 5084,(2009)2.

Junya Ide et al, Jpn J. Appl. Phya. 38, 2049,(1999)

3.

K. Kajikawa et al, Jpn. J. Appl. Phys. 30(5), 1050,(1991)

17

Nonlinear optics polymers excited by surface plasmon enhanced field in Kretchmann configuration
Shizuoka Univ.

Y. Ono, K. Suto, T. Sato, A. Ono, W. Inami, Y. Kawata, and A. Sugita

Introduction
Optical properties of meal thin films or metal nanostructures related to surface plasmon
resonance, have attracted great interests. Upon the photo excitations of the surface plasmons theintense optical fields appear in the vicinity of the metal surface and the field intensities are two or
three magnitudes higher than that of the incident light waves. Taking advantage of the intense
optical fields, due to the surface plasmon, a lot of novel optics and optronics for nanotechnologies
and nanosciences are proposed. Especially, a lot of researchers pay attentions for their applicationsof the drives for high energy quantum beams. The intensity of the surface plasmon enhanced opticalfields pumped by a few nJ femtosecond optical pulses is high enough to generate higher orderharmonics or to accelerate electrons with keV kinetic energies.
On the other hand, there are not so many reports dealing with their applications to the lower
order nonlinear optics such as second order or third order nonlinear optics. It is probably because
the small nonlinearities of the metals were quite small because of their conductivities. It seems tobe effective to fabricate materials with large nonlinearity on the metal surface to enhance thenonlinearity of the metal surface where the surface plasmon-enhanced optical field is created.
In the present study, we will report the second–order nonlinear optical interactions between the
nonlinear polymers and the surface plasmon enhanced optical fields. Our experimental result
indicated that second–order nonlinearity of the metal surface was efficiently enhanced by coating
the polymer materials.
TheoryFirst, the surface plasmon resonance conditions for the silver thin films coated with the NLO
polymer films were examined theoretically with a multiple wave interference model. The model
system consisted of four layers, that is, a BK7 glass, the silver thin films, the NLO polymer thinfilms and the air. In the calculations, the refractive indexes of the BK7, the silver, the NLO polymer
and the air were 1.51078 , 0.148431 and 1.0, at 800 nm respectively . The thickness of the silver film
was fixed at dAg=40 nm while determined by changing dpolymer the thickness of the NLO polymers
were changed between 0 and 100 nm.
Figure 1 (b) shows the reflectivity of the systems against the incidence angles of the excitation
light. The dip structures, corresponding to the surface plasmon resonance, are seen in the curves.
The position of the dip is dependent on the thickness of the NLO polymer layers and it becomeswider as the film thickness is thicker. Fig. 2 (a) shows the field intensity inside the polymer layers.
The field intensity is represented by the values at the deepest positions of the dip. Assuming thatthe extinction coefficient of the NLO polymers is negligible, the field intensity of the optical field is
not attenuated inside entire the polymer layers. The field intensity becomes lower as the polymer
18

Figure 1 (a) Schematics of model system for determining the surface plasmon resonanceconditions. (b) Incidence angle dependence of the reflectivity of the polymer coated Ag films
film thickness is wider.
The second harmonic (SH) intensities are expressed with an Equation (1).
…(1)
Here, η, l, and dNLO, are the enhancement factor of the incident optical field Ein, the polymer
thickness and the nonlinearity of the nonlinear coefficient polymers, respectively. Assuming thatthe nonlinearity dNLO is independent of the polymer layer thickness, the SH intensity ISH isdependent on the polymer film thickness as shown in Fig. 2(b). The curve indicates that SHconversion efficiency is the highest at the polymer thickness of d=50 nm. The SH conversion
efficiencies were determined by the balance between the enhancement factor of the electric fields
and the light – matter interaction lengths.

Figure 2(a) Increase the intensity of the optical field in the portion of each polymer film
thickness. (b) A secondary non-linear optical polarization is excited in the polymer of various
thicknesses.

Experimental
The surface plasmons were excited with the attenuated total reflection method using a prism.
The samples for nonlinear optical spectroscopy consisted of three-layers. The silver layers, were
deposited on the flat surface of the BK7 glass prism, above which the NLO polymer films were
deposited.The silver thin film was deposited by a vacuum evaporation method.The thickness of the19silver films was 40 nm. On the other hand, the polymer films was prepared by a spin coating
method. By controlling the concentrations and rotational speeds, the thickness of the polymers were
controlled between 10 and 100 nm .The NLO polymers consisted of host –guest complex structures.
The guest chromophores for nonlinear light-matter interactions, was Disperse Red 1, play, while thehost materials for fixing the positions of the guest clomophores was poly (methyl methacrylate). In
general, the materials for second order nonlinear optical susceptibilities should be lack of inversion
symmetry.

In the present study, the non-centro symmetric structures were induced withnonelectrical poling effects proposed in our previous studies.

The polar ordering of the NLO

chromaphores was induced by taking advantage ofthe surface alignment effects and polarization
orientations of the host polymers.
Fig. 3 shows the experimental apparatus formeasuring the second harmonic generations under
the surface plasmon resonance conditions. The
excitation light source is femtosecond optical pulses
from Ti:sapphire regenerative amplifiers . The
center wavelength, the pulse width and the pulse
energies were 800 nm, 150 fs, 1 mJ, respectively.
The beam diameter on the sample surface wasapproximately φ5mm.

The pulse energies of theexcitation lights were attenuated with natural

Figure 3 An experimental apparatus
system for observing the second harmonic
generation in a nonlinear optical polymer
optical field excited by surface plasmon
enhanced optical fields.

densities filters and it was 20 μJ on the samples .The SH signals were detected with a photo
multiplier tube after separating the fundamental lights with a color glass filter. The pump beampolarization angle dependence of the SH signal was studied, while their polarization angle
dependence was also resolved.
Results and Discussion
Figure 4 (a) shows the SH signal intensity as a function of the incidence angles of the excitation
lights. The polarization of the excitation beams was p-polarized and the p-polarization componentsof the SH signals were recorded. Here, the data correspond to the samples with the polymer film
thickness of 15 and 40 nm. As a reference, the data of the polymer uncoated silver films uncoatedwith the polymer films is also shown. Both of the polymer–coated and uncoated silver films exhibit
a dip structure at the critical angles sp, where the surface plasmon resonance conditions are
satisfied. The polymer uncoated silver film exhibit the dip at sp =41.2 °. The position of sp depends
on the polymer film thickness and it is wider as the polymer film thickness is thicker. The width ofthe dips was wider as the polymer film thickness is thicker. These observations are consistent withthe expectation indicated with the theory based on the multiple wave interference models. On theother hand, the samples emitted the SH signals and the intensities of the signal were the highest at20

the critical angles sp.
Figure 4 (b) is plotted as afunction of the intensity ofthe excitation light intensity

Ipump

SHG.

Hence,

itisconcluded that the SH signal
was excited by the surface
plasmonenhanced

opticalfields.

The

signalSHintensities were plotted as afunction of the excitation

Figure 4(a) The reflectivity and SHG from the polymer coated Ag
films as a function of the incidence angles. (b) Excitation pump
power dependence of the SHG signals.

light Ipump was proportional to the square of the excitation light intensities Ipump. The SH signal
intensities from the polymer – coated Ag films were much higher than those from the polymer –uncoated Ag films. The second order NLO susceptibilities of the polymer – uncoated Ag films wererelated to the nonlinear polarizations excited by the surface plasmon enhanced optical fields in thepolymers.
Fig. 5 shows the SH signal intensities of thepolymer coated Ag films as a function of the polymer
film thickness. The data is represented by the value
at the critical incidence angle sp. The SH conversion
efficiency was the highest from the sample with the40

nmpolymerfilm

thickness.

The

present

experimental results were quantitatively consistent

Figure 5 SHG intensities as a function of
the polymer of various thicknesses

with the expectations presented by the models using
the multi wave interference. However, the curve can not be reproduced well with the theoreticalresults shown in Fig. 2(b). The discrepancy between the experimented and theoretical results is
probably not substantial. As one of the probable reason, the polymer films are not uniform and theroughnessmaystimulate

unexpectedenhancement of the optical fields.
Figure 6 shows the dependence of thepolarization angle of the excitation light p.
Here, the thickness of the polymer film was
15nm. The experimental results are well
reproduced with function cos4p. The result
indicatesthatpolarizations

the

were

non-linear

excitedonly

opticalbyFigure 6 (a) Polarization dependence of thetheexcitation light polarization dependence ofp-polarized pump beams. The polarization of

second harmonic light intensity (b) the second

the SH signal was resolved with the polarizer

harmonic light.
21

and it is shown in Fig. 6(b). The data is well reproduced by cos2a function. This result indicates that
the SHG signal is p-polarized.
In general, second-order nonlinear susceptibility of the NLO host - guest polymers is expressedwith a linear combination , three independent tensor components of d33, d31 (=d32) ,d24 (=d15). The
present p and a dependence means that the nonlinearity is only related to the d33 components. The

p-polarized components of the pump beams excite the surface plasmon enhanced optical fields inthe direction normal to the surface of the Ag films. The nonlinear polarization occurred in the
direction normal to the Ag film surface in the NLO polymer.
Conclusions
In this study, we have examined the second-order nonlinear optical susceptibility of surface
plasmon resonance conditions in the silver thin film coated with polymer. The second ordernonlinear optical susceptibilities of the polymer can be excited with the surface plasmon enhanced
optical fields in the Ag films. The SH conversion efficiency the highest SH conversion efficiency was
obtained from the sample with the 40 nm polymer films. The optimized conditions for the SH
conversion were determined by the balance between the polymer – optical field interaction lengths
and the enhancement factor of the optical fields.
Reference
1.

S. E. Irvine et. al. Phys. Rev. Lett. 98, 184801 (2004).

2.

S. Kim et. al. Nature, 453, 757 (2008).

3.

A. Sugita et. al. Optical Material Express 2, 1588 (2012).

22

Development of rare earth doped Y2O3 fluorescent thin film for electron beam assisted optical
microscope
Masashi Kamiya, Aki Miyake, Yasunori Nawa, Wataru Inami, Atsusi Sugita,
Hiroko Kominami, Yoshimasa Kawata, Yoitiro Nakanishi
Abstract
Here we report the development of luminescence thin film for Electron-beam eXitation Assisted(EXA) optical microscope system as new novel super-imaging microscope. The luminescence thinfilms consisting of Eu3+ doped Y2O3 were prepared with an electron beam evaporation method. The
films with the thickness between 80 nm and 200 nm were prepared and they were annealed at thetemperatures between 500℃ and 1000℃. The intensity of the cathode luminescence signals wererecorded as functions of the film thickness and the electron acceleration voltages. The optimized
conditions for fabricating the luminescence films will be reported in terms of the film thickness andthe accelerating voltage and the annealing temperatures.
Introduction
Several super-imaging microscopy techniques, which enable us to records the images with thespatial resolutions smaller than diffraction limit, have been studied extensively. Two-photon
excitation fluorescence microscope [1], second and third harmonic optical microscopes [2], Coherent
Anti-Stokes Raman Scattering (CARS) microscope [3] are some of the most promising ones. Since we
can operate the microscopes in the air atmosphere, they are suitable for observing biomedical
samples, such as living cells and tissues. However, the in spatial resolution is at most few hundred
nanometers.
Recently, we proposed Electron-beam eXaitation
Assisted (EXA) optical microscope [4] as new super
imaging microscope. The light sources of the EXA
microscope cathode luminescence light emitted byinelastic scattering of the high energy electron beam.
Since de Broglie wavelengths of the electrons with~keV kinetic energies is much smaller than angstrom.
In principle they can be focused in the area smaller
than nanometer scales. Hence, the luminescence lightwaves should spread in the area much smaller than thediffraction limit just after they are emitted from thematerials. In our previous study, we made an
examination about the spread of the luminescence inthe thin films excited by electron beams with sever keVkinetic energies with Monte Carlo simulation methods.
23

Figure1 Schematics of EXA microscope

When the film thickness was thinner than 50 nm the spread of the luminescence was smaller than
50 nm.
It should be noticed that EXA microscope enables us to measure the images in the air
atmospheres. The substrates separate the vacuum atmosphere for air atmosphere. The specimens
are put on the front side of the luminescent films, while the electron beams are irradiated from theback in the vacuum. Supposed that the film thickness is narrower than the penetration depth of theelectron beams, the luminescence light waves penetrate to the front side of the substrate. In ourprevious study, we chose Si3N4 substrate as a luminescent films. The Si3N4 is famous as theconstitutional materials. The Si3N4 substrates with the thickness as narrow as 50 nm is stiff enoughto separates the vacuum atmosphere from the air atmosphere.
In our previous studies, we succeeded in imaging the polystyrene latex beads with ~50 nm
diameter with the sufficient spatial resolutions. The lights were due to the luminescent from the
Si3N4 substrate was the near-ultraviolet. If the EXA microscopes are operated with visible
luminescence lights their applications will covers much fields.
Some of the rare-earth doped materials seem to satisfy the demands for the visible luminescentwider for the EXA microscope films. There materials have been used as the visible light emitters forthe florescent light tube. In the present study, Eu - doped Y2O3 was chosen as the visible

Figure 2 Schematics of luminescent thin films for EXA microscope.
luminescent emitters for the EXA microscope. The films were fabricated on the Si3N4 substrates asshown in Fig. 2. We will also optimized conditions for the demonstrations of the EXA microscopewith the Y2O3 luminescent films. The fabricating the thin films will be reported.
Experimental
The Y2O3: Eu thin films were fabricated on Si3N4 substrates with electron beam evaporation
method. First, the powders of Y2O3 and Eu2O3 were mixed and pressed into pellet forms. The pellets
were sintered at 1000℃. The concentration of the Eu3+ ion in the material was 2 mol %. The
evaporation was done in the vacuum chamber in which the pressure was set to approximately 10-6
Torr. The electron beams were accelerated under the conditions of 4kV and 50 mA current. The film
thickness was monitored by a quartz crystal microbalance method. The degree of crystallinity ofluminescent thin films was low because the oxygen vacancies. The films were annealed at thetemperatures between 500 and 1000℃ under the flow of the oxygen gas for 3 hours in order to fill
the vacancies and improve the crystalinities.
24

The structural properties of the films were characterized with X-ray diffraction patterns (XRD) andAtomic Force Microscope (AFM). The optical properties of the films were studied with a cathodeluminescence spectroscopy. Finally, the imaging the polystyrene (PS) latex beads with φ ~100 nm
was conducted with the Y2O3: Eu luminescence thin films.
Results and Discussion
(c)

(a)

Fig. 3 CL measurement (a)CL intensity dependence of the acceleration voltage which is emitted
from the phosphor thin film by electron beam irradiation. (b) Luminescence image of the thinfilm emitters. (c)the dependence of the emission intensity for the thickness of the thin film
emitters.
Fig. 3 (a) shows the acceleration voltage dependence of the CL intensity from Y2O3: Euluminescence thin films on the Si3N4 substrates. Fig. 3 (b) shows the images of the luminescencefilms irradiated by the electron beams accelerated with the different voltages. Here, the thicknessof the films was 200 nm. The films emitted the luminescence signals at the acceleration voltage
higher than 2 kV. The electron beams with the kinetic energies smaller than 2kV could not
penetrate the Si3N4 substrates and could not excite the Eu3+ ions in the luminescent thin films.
Fig. 3 (c) shows the CL intensities against thefilm thickness the Y2O3：Eu film thickness. The
accelerating voltage was 5kV. Only the films withthe thickness thicker than 85 nm emitted the CL(222)

signals.
films annealed at the different temperatures
between 500 and 1000℃. The thickness of theY2O3: Eu films were 200 nm. The films were

(400)

(211)
intensity［a.u.］

Fig. 4 (a) shows the picture of Y2O3: Eu thin

(440)

1000℃
900℃
700℃
500℃

irradiated by the ultraviolet lights with 254 nm
from a high pressure Hg lumps. Film emittingstronger photoluminescence has a tendency ofbrighter cathode luminescence. The films annealed
at higher temperatures emitted brighter photo
luminescence.
Fig.4 (b) shows the X - ray diffraction patternsof the Y2O3: Eu thin films annealed at different
25

Powder(622)

as-depo2030

40
2θ［deg.］50

60

Figure4 (a) XRD pattern of Y2O3:Eu thinfilm annealed at different temperatures.
Image of Y2O3:Eu thin films irradiatedby the black lights. The samples annealed
at different temperatures are showntemperatures. The as-deposited films were also shown as a reference. After the annealing
procedures, all the diffraction peak intensities increased. The peak positions of the thin films were
almost the same as those of the powder samples. Hence, the crystal structures of the thin films were
cubic one like that of the powder samples [5]. It should be remarkable that was shifted during theannealing procedure. The result indicated that the crystallinity of the thin films were improved fillby the oxygen atoms in the vacancies in the crystals. Furthermore, the peak positions of the (222)diffraction was different from that of powder samples. Using Bragg equation, the lattice spacing
due to the (222) diffraction were determined to be d = 6.13 nm for the powder sample and d = 6.08
nm for the film sample.
The Y2O3 crystal belongs to the cubic groups with a unit length a = 10.60 Å. The lattice spacing
along (222) plane is 15.00 Å. On the other hand, the Si3N4 crystal belongs to the hexagonal groups
with unit lengths a = 7.61 Å, and c = 2.90 Å. The lattice spacing of the (222) plane of Y2O3 is d isalmost as twice as the unit length a = 7.61 Å of the Si3N4 crystal. It is natural to conclude that the(222) plane of the Y2O3 crystal is jointed on the (001) plane of Si3N4 crystals. In the junction, thelattice mismatch between two crystals is 1.40%. In general, when the degree of the mismatch islarger than 1%, the lattice distortionis significant at the boundaries. In
thepresent

case,

the

latticemismatch is larger enough to makesignificant

distortions

in

the

boundary area.
Fig. 5 shows the AFM images of
the

thin

films

temperatures

annealed

between

500

at
and

1000 ℃ . The images of the asdeposited films are also shown as areference. The measurements wereconducted in the square area 500 ×
500

nm.

The

surfaceoftheas-deposited films consisted of theaggregates of the small particles

Fig. 5 AFM (a) As-deposited samples and (b) the samples
annealed at 500, (c) 700, (d) 900, and (e) 1000 ºC.

with after the annealing procedures, the particle size became larger as the annealing temperatures
were higher. During the annealing procedures, the atoms diffused so as to grow the grain size of theparticles.
Finally, the EXA microscope image of the polystyrene latex was shown in Fig. 6 (a). Here, thepolystyrene latexes with average diameter of 100 nm were scattered on the Y2O3: Eu thin films. The
SEM image of the same sample is also shown in Fig. 6 (b). The accelerating voltage of the electron
beams was 5 kV and the electron current was 270 pA. In both of the pictures, the white spots due to26

the PS latexes can be seen at the same
corresponds positions. Hence, it was concluded
that the spatial resolution of the EXA microscopewith Y2O3: Eu thin films was at least 200 nm, andthe microscope could record the image with the
sub diffraction resolution on the present stage.
Fig. 6 Spatial resolution evaluation when put

Conclusions
In this presentation, we report the fabricationsof Y2O3: Eu thin films as the luminescent emittersthe latex beads on a substrate (a) SEM image(b) EXA image

for the EXA microscope. Our experimented result indicates that the cathode luminescence from theY2O3: Eu thin films are suitable for the light sources for the EXA microscope. The optimized
fabrication conditions were determined in terms of the film thickness and the annealing
temperatures. The conversion efficiency of the cathode luminescence was higher at the higher
annealing temperatures. The oxygen vacancies were filled and the crystallinity improved more
effectively at the higher annealing temperatures. The intensity of the CL signals is also dependent
on the accelerating voltage, and the luminescence occurred only at the accelerating voltage higher
the 5 kV. The intensity of the CL was also dependent on the accelerating voltage and the most
optimized conditions in the present stage has not yet to be determined, and we will report thefurther progress in the presentation.
References
1.

F. Helmchen, D. W. Tank, and W. Denk. App. Opt. Vol. 41 (15), 2930-2934 (2002).

2.

C. Hongtao, W. Haifeng, and S, Mikhail. Opt. Exp. Vol. 17 (3), 1282-1290 (2009).

3.

M. S. Smith, B. Srivastava, and P. Moica, Opt. Exp. Vol. 18 (23), 23796-23804 (2010)

4.

W. Inami, K. Nakajima, A. Miyakawa and Y. Kawata. Opt. Exp. Vol.18 (12), 12897 (2010) .

5.

(b)15 (1984).
A. Zur and T. C. McGill, J. Appl.Phys.Vol.55 (2),27