「様式 3」

P-45

Laser-induced creation of long lifetime fluorescencecenters in chromone-based materials for development ofimaging formation techniques[1] Organization
Project Leader: Kateryna Zelenska, M.Sci.,
Engineer (Taras Shevchenko National
University of Kyiv, Ukraine).
Representative at RIE: Toru Aoki, Ph.D., Prof.
(Research Institute of Electronics, Shizuoka
University, Japan).
Participants:
Sergey Gagarsky, Ph.D., Senior Scientist(Saint-PetersburgNational
Research
University of Information Technologies,
Mechanics and Optics, Russia).
Volodymyr Gnatyuk, Ph.D., Assoc. Prof.,
Senior scientist (V.E. Lashkaryov Instituteof Semiconductor Physics of the National
Academy of Sciences of Ukraine, Ukraine).
[2] Progress of Scientific Activity
The CRP participants used communication
facilities to discuss the collaborative projectwork and personally met, when Prof. Toru Aoki
visited Ukraine for attending conferences in
September and October 2015 and when
Ukrainian project members visited RIE in
September (The 14th Intern. Conf. on Global
Research & Education: Inter-Academia-2015)
and also in November 2015 – January 2016
thanks to support from CRP.
Apart from the investigations, described in
the next section, the CRP team membersorganized the cooperative meetings in Ukraine
and participated in the scientific forums inUkraine and Japan to discuss the issues related
to the project and establish collaboration andinformation exchange between Ukrainian andJapanese scientists and students. In particular,
more than 10 students of Shizuoka University
visited Ukrainian Universities in October 2015.
• Ms. K. Zelenska and Dr. V. Gnatyukorganized workshop “Education and Researchin Shizuoka University” in Chernigiv National
University of Technology, Ukraine (Sep. 2015)
where Prof. T. Aoki made his talk and Ms. K.
Zelenska reported about scientific andeducation exchange programs for Ukrainian
researchers and students to visit Japan.

• Ms. K. Zelenska and Prof. T. Aoki organized
the meting of Ukrainian and Japanese students
at Chernigiv National University of Technology,Ukraine (Oct. 2015) to exchange the knowledge
and information about education and researchin Japanese and Ukrainian universities.
• Ms. K. Zelenska and Prof. T. Aoki organized
the friendly meting of Ukrainian and Japanese
students at the Ukraine-Japan Center in Oct.
2015 to discuss the issues of culture, educationand scientific activity in Ukraine and Japan.
• Ms. K. Zelenska presented the projectrelated results at The 14th Intern. Conf. on
Global Research & Education: Inter-Academia2015) held at Shizuoka University (28-30 Sep.
2015, Hamamatsu, Japan).
• Ms. K. Zelenska and Prof. T. Aoki weremembers of the Organizing Committee and Dr.
V. Gnatyuk was a member of the International
Committee of The 16th Intern. Young Scientists
Conf. “Optics & High Technology MaterialScience” SPO 2015 held at the Faculty ofPhysics of Taras Shevchenko National
University of Kyiv (22-25 Oct. 2015, Kyiv,Ukraine).
• Ms. K. Zelenska presented the projectrelated results at the Monday Morning Forum atResearch Institute of Electronics, Shizuoka
University (30 Nov., 2015, Hamamatsu, Japan).
This presentation was made owing to thebusiness trip supported by CRP.
[3] Research Results
Short pulses of focused laser radiation havethe unique capacity to change the properties ofa small local area in the bulk of transparent
objects because of non-ideal opticaltransparency of the employed material, its
absorptive inhomogeneities (defects, inclusions,density fluctuations, etc.) and non-linear
phenomena (multiphoton absorption, etc.) [1-7].
The project has been devoted to analysis andevaluation of laser-based techniques andtechnological approaches of formation of
micromarks in the bulk of different materials
transparent for a selected laser wavelength,which can serve as pixels for creation of images
as well as information carriers for 2D and 3D
digital optical recording. In particular, physicaland photochemical processes occurring in thebulk of transparent light sensitive chromonebased materials under the action of focused
short laser pulses were studied.
In conventional optical recording methods,
crosstalk or interference of different recording
components (marks) and layers often leads toreduced recording densities. It is possible,
however, to improve the spatial resolution andthus the density of digital optical recording byusing laser-induced marks which act as lightemission centers under backlight illumination.
The most promising materials for such a
purpose are those in which a local change in thecomplex refractive index, structure or spectralluminescent properties occurs in result of multiphoton absorption of ultrashort pulses ofrecording radiation [1-3, 5-7].
Organic molecules of chromones embedded
in polymer matrix are promising media for
optical data recording based on multiphoton
absorption [3, 5-7]. These compounds can beirreversibly converted from the non-fluorescentform A to the stable fluorescent photoproduct C.
(Figs. 1 and 2). The absorption spectrum of thephotoproduct shows an additional excitation
band in the visible range (400 nm), which was
not observed in the state A. Thus, opticalexcitation in the spectral range between 400 and
500 nm leads to the stable fluorescencephotoproduct C.

Fig. 2. Chromone compound: (1) – initial absorption
spectrum in A state, (2) – fluorescence excitation
spectrum in B state, (3) – fluorescence spectrum for
C state.

Emitting centers can thus be obtained inthermally stable photosensitive organic
chromone-based materials in selected layers by
two-photon absorption of laser radiation with awavelength that is not absorbed by the polymer
matrix and chromone molecules [3, 5-7].
Separate organic molecules in the laser
focal area change their structure because of
two-photon absorption and they become
fluorescent marks. The density of created marks
depends on the energy and number of recording
laser pulses. The distance between theneighboring emitting centers created in thepolymer matrix with embedded chromone
molecules by short laser pulses of a YAG:Ndlaser (λ = 532 nm, τ = 0.8 ns) is about 5 µm andmark sizes are less than 2 µm (Fig. 3). The
brighter marks were created by increasing thenumber of recording laser pulses. Fig. 4 shows
marks obtained as result of two-photon
absorption at different laser intensity:
fluorescence centers (a) and damage points (b).

Fig. 3. Micrograph of laser-induced fluorescentmarks formed in the volume of an organic
chromone-based material by laser irradiation.

Fig. 4. Samples of fluorescent centers (a) anddamage points (b) obtained under investigation of
two-photon absorption in organic chromone-basedmaterials.

Fig. 1. Transformation of the chromone molecule
structure because of two-photon absorption and it
becomes fluorescent centers (light-emitting marks).

2[4] Publications (published and submitted by
the CRP participants during the project
period 29.05.2015-06.03.2016)
1. V.A. Gnatyuk, O.I. Vlasenko, S.N. Levytskyi, T.
Aoki, V. Mizeikis, S.V. Gagarsky, K.S. Zelenska,
D.V. Gnatyuk, Laser-induced creation of marks
as information carriers for digital recording,
Program & Technical Digest, LAPM2015 - The
7th Intern. Congress on Laser Advanced
Materials Processing, 2015, Th2-LO-17, 185.
(26-29 May 2015, Kitatyushu, Japan).
2. V.A. Gnatyuk,
O.I. Vlasenko,
S.N. Levytskyi,
T. Aoki,V. Mizeikis,
S.V. Gagarsky,K.S. Zelenska,
D.V. Gnatyuk, Laser-induced creation of marks
as information carriers for digital recording,
Proceed. of LAMP2015 - the 7th Intern. Congresson Laser Advanced Materials Processing, (2015)
5 pages.
3. A. Ayt, V. Barachevsky, V. Kiyko, S. Gagarsky,
A. Sergeev, A. Veniaminov, M. Krayushkin,
H. Iglev, Two photon absorption and luminescentcenters forming in photoswitchable media for
multilayer optical disks, Abstracts of The 10thPhenics Intern. Network Symp. “Photoswitchable
Molecular Systems and Devices: From Synthesis
to Applications”, 2015, 47. (23-26 Nov. 2015,Cargese, France).
4. K.S. Zelenska, S.E. Zelensky, L.V. Poperenko,K. Kanev, V. Mizeikis, V.A. Gnatyuk, Thermal
mechanisms of laser marking in transparent
polymers with light-absorbing microparticles,Optics & Laser Technology, 76, (2016) 96-100.
5. V.A. Gnatyuk, O.I. Vlasenko, S.N. Levytskyi, T.
Aoki, V. Mizeikis, S.V. Gagarsky, K.S. Zelenska,
D.V. Gnatyuk, Capabilities of laser-induced
marks as information carriers created in different
materials,
JournalofLaser
Micro/Nanoengineering, (2016), in press.
6. A, Ayt,
V.A. Barachevsky,
S.V. Gagarskiy,
V.V. Kiyko,
A.N. Sergeev,
Y.Y. Sukhikh,
A.V. Veniaminov, V.V. Zakharov, Fluorescent
properties of chromone-class isomers converted
by single- and multiphoton excitation, The 17th
Intern. Conf. “Laser Optics 2016” (LO’2016),
2016, 1 page. (27 June - 1 July 2016, SaintPetersburg, Russia), submitted.
A. Ayt,V.A. Barachevsky,
7. S.V. Gagarsky,
A. Duensing,
H. Iglev,
V.V. Kiyko,
M.M. Krayushkin, A.N Sergeev, V.V. Zakharov,Thresholds for two-photon recording offluorescent centers in chromone-doped polymer
films, Intern. Symp. “Fundamentals of Laser
Assisted
Micro–andNanotechnologies”(FLAMN-16), 2016, 1 page. (27 June - 1 July
2016, Saint Petersburg, Russia), submitted.

After UV irradiation

Before UV irradiation

The different number of laser pulses incident
to the local area of a given mark leads tocreation of different number of induced
fluorescent centers and thus to different
brightness level. Fluorescent marks withspecific intensities can therefore be created bymulti-shot laser irradiation and careful selectionof the applied number of laser pulses. The
resulting light emitting marks can consequently
be read and classified in respect to theirbrightness by standard photodetection methods.
Since even a single molecule of chromone
can serve as a fluorescent center and thewaveguide layer thickness is limited by thereading radiation wavelength, the maximum
recording density depends only on therecording laser beam caustic parameters.
Embedded information can in fact be readby injection of UV radiation into waveguidelayers located between the photosensitive layers.
In such a case the UV radiation partiallypenetrates into the adjacent layers withrecorded marks and excites light emission fromthem due to fluorescence. Given that even asingle chromone molecule can act as afluorescent center and that the thickness of awaveguide layer can be as low as the reading
radiation wavelength, the maximum recording
density and spatial resolution depend only on
the caustic of the recording laser beam and canclosely approach the known theoretical limits.
The recording carried out by multi-photon
excitation of organic molecules (photochromogenic chromones) and transition of them
to a thermo-stable fluorescent state is mucheffective compared with another processes
based on photoluminescence or refractive index
change [3, 5-7].
Compounds consisting from chromones anddiarylethenes are promising materials for data
recording, optical switches and imaging. (Fig.5).

Fig. 5. Organic photosensitive chromone-based
compound becomes light-emitting material after
ultraviolet irradiation.

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Traveling Report
Name:
Affiliation and address:
Period of time:
Destination:
Purpose:Name of receiver:

Kateryna Zelenska
Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska
Street, Kyiv, 01601, Ukraine
15 November 2015 – 13 January 2016
Research Institute of Electronics, Shizuoka University
Study of laser technological approaches suitable for volumetric optical
recording and image formation by creation of micromarks in the bulk ofdifferent materials, particularly in transparent light sensitive chromonebased materials under action of focused short laser pulses.
Participation in scientific meetings at Research Institute of Electronics,
Shizuoka University during the period of stay.
Prof. Toru Aoki

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