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Feature Frontiers of research on solar cells: Lead (Pb) perovskites with efficiencies over 20%

News and Events
 UEC hosts Japanese Neural Network Society Workshop on "Data-driven approach for understanding cerebellar
mechanisms on eye movement control" UEC launches the Info-Powered Energy System Research Center (iPERC)
 Delegates from Binghamton University, State University of New York, visit UEC

Research Highlights
 Nanowire quantum dot solar cells: oxide layer boosts performance Motor behaviour: understanding the jerks that lurk in smooth movements

Topics UEC students receive prestigious awards at international conference A career in ultrashort pulse lasers, ultrafast spectroscopy, and quantum information

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Frontiers of research on solar cells: Lead (Pb) perovskites with efficiencies over20%
Qing Shen, associate professor at the Department of Engineering Science, Faculty ofInformatics and Engineering at UEC, Tokyo.
25 April 1954 was a seminal day in the history of research on solar cells. On this datescientists at Bell Labs, Murray Hill, USA, announced the invention of the world's firstpractical panel of solar cells for converting sunlight into electricity. The solar cells weremade of silicon and had an efficiency of 6 percent--a tremendous achievement even by

Assoc. Prof.
Qing Shen

today's standards. Notably, the solar cells were used to power a radio transmitter andenergize a motor to drive a Ferris wheel--both practical applications of solar cells.
Fast forward to 2015 and silicon-based solar panels are ubiquitous. They have become an indispensable meansof generating energy for human habitats, space exploration, and wearable devices such as wrist watches.
Now, at the research level, scientists are innovating to produce even more efficient solar cells at low cost,using environmentally friendly materials. Notably, recent reports of solar cell conversion efficiencies of
20.1% for cells fabricated using organometal trihalide perovskite have caught the imagination of scientists inthe search for high performance, cheap solar cells.
"This very high 20% efficiency exhibited by organolead halide perovskite solar cells has galvanized scientists
to focus on understanding the physics of this material system," says Qing Shen, associate professor at the
Department of Engineering Science, Faculty of Informatics and Engineering at UEC. "Two of the main issues
to resolve are clarifying why organolead halide perovskites yield such a high efficiency, and potential
alternatives to lead based perovskites."
The material properties governing the high conversion efficiency of perovskite-based organic/inorganic solidstate solar cells (OIHSCs ) include their direct band gap and high optical absorption; large dielectriccoefficient leading to smaller exciton binding energy; long photoexcited carrier lifetimes; no deep level
defects; and very small Urbach energy.
"Our research is focused on clarifying the physical properties of this material that are responsible for such ahigh conversion efficiency," says Shen. "More specially, we are studying the relationship between carrier
lifetime, charge separation and charge recombination dynamics and the performance of photovoltaic
perovskite-based OIHSCs."
Shen has developed a dedicated transient absorption (TA) system to measure charge separation andrecombination dynamics from the sub-picoseond to milli-second range. Recent experiments shows perovskite
The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

CH3NH3PbIxCl3-x to show long carrier lifetimes in the micro-second range and charge separation efficiency of
TiO2/CH3NH3PbIxCl3-x/Spiro to be as high as 90%.
"Decreasing the recombination at TiO2/Spiro OMeTAD interface is a critical factor for improving theefficiency," says Shen. "Other issues are devising methods to suppress recombination, surface passivation of
TiO2, and interface engineering."
Further improvements in the efficiency of these solar cells are expected by capturing more light from the nearinfra-red region of the spectrum. Professor Shuzi Hayase of the Kyushu Institute of Technology, leader of the
JST CREST research group--which Shen has recently joined-- has reported that this can be achieved by using
a 'Sn/Pb cocktail perovskite' in the form of CH3NH3SnxPbI1-xI3 perovskite solar cells that cover the spectral
range up to 1060 nm.
Shen and colleagues have combined transient absorption with photoacoustic spectroscopy to analyze theproperties of these materials to improve the Jsc, Voc and FF of Sn/Pb cocktail perovskite solar cells. Initial
findings indicate that better solar cells could be produced by reducing non-radiative recombination by
improving the crystalline quality of the Pb/Sn perovskites and suitable passivation of the TiO2/Sn/Pb
perovskite interface, and realization of pinhole-free perovskite films.
"This is an exciting time to be involved in solar cell research," says Shen. "This is interdisciplinary researchrequiring many different skills. I am currently working with Professor Shuzi Hayase at Kyushu Institute ofTechnology and other collaborators on producing high efficiency, inexpensive perovskite organic/inorganic
solar cells."
Further information
SHEN GROUP: http://www.shen.es.uec.ac.jp/introduction.htm (in Japanese)
1. Qing Shen,* Yuhei Ogomi, Jin Chang, Taro Toyoda, Kosei Fujiwara, Kenji Yoshino, Koki Sato, Kouhei
Yamazaki, Masaya Akimoto, Yuki Kuga, Kenji Katayama, and Shuzi Hayase*: Optical Absorption, Charge
Separation and Recombination Dynamics in Sn/Pb Cocktail Perovskite Solar Cells and Their Relationships to
Photovoltaic Performances, J. Mater. Chem. A, 2015, 3, 9308-9316, DOI: 10.1039/C5TA01246E.
2. Qing Shen,* Yuhei Ogomi, Jin Chang, Syota Tsukamoto, Kenji Kukihara, Takuya Oshima, Naoya Osada,
Kenji Yoshino, Kenji Katayama, Taro Toyoda and Shuzi Hayase*: Charge transfer and recombination at themetal oxide/CH3NH3PbClI2/spiro-OMeTAD interfaces: uncovering the detailed mechanism behind highefficiency solar cells, Phys. Chem. Chem. Phys., 2014,16, 19984-19992, DOI: 10.1039/C4CP03073G
3. Yuhei Ogomi *, Atsushi Morita, Shota Tsukamoto, Takahiro Saitho, Qing Shen *, Taro Toyoda, Kenji Yoshino,
Shyam S. Pandey, Tingli Ma, and Shuzi Hayase*, All-Solid Perovskite Solar Cells with HOCO-R-NH3+IAnchor-Group Inserted between Porous Titania and Perovskite, J. Phys. Chem. C, 2014, 118 (30), pp
16651-16659, DOI: 10.1021/jp412627n.

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4. Yuhei Ogomi,* Kenji Kukihara, Qing Shen,* Taro Toyoda,Kenji Yoshino, Shyam Pandey,Hisayo Momose,and
Shuzi Hayase*: Control of Charge Dynamics through a Charge-SeparationInterface for All-Solid
Perovskite-Sensitized Solar Cells, CHEMPHYSCHEM, 2014. DOI: 10.1002/cphc.201301153.
5. Yuhei Ogomi,* Atsushi Morita, Syota Tsukamoto, Takahiro Saitho, Naotaka Fujikawa, Qing Shen, Taro
Toyoda, Kenji Yoshino, Shyam S. Pandey, Tingli Ma, and Shuzi Hayase*: CH3NH3SnxPb(1−x)I3 Perovskite
Solar Cells Covering up to 1060 nm, J. Phys. Chem. Lett.. Vol. 5, 1004−1011 (2014)
dx.doi.org/10.1021/jz5002117

Top-view SEM image of (a) TiO2/MASn0.5Pb0.5I3 perovskite and (b) TiO2/MASn0.5Pb0.5I3 perovskite/P3HT samples.
The scale bar is 1 μm in both images.

Optical absorption spectrum of MAPbI3 and Sn/Pb cocktail MASn0.5Pb0.5I3 perovskite measured using a photoacoustic (PA)technique. The bandgap energy and Urbach energy were determined to be 1.21 eV and 34 meV, for MASn0.5Pb0.5I3 perovskite,and to be 1.52 eV and 22 meV for MAPbI3, respectively.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

(EG/q)-Voc versus Urbach energy for our samples and for typical photovoltaic materials at room temperature which were reported
by Wolf and co-authors in J. Phys. Chem. Lett. 2014, 5, 1035-1039. The higher loss in Voc for CH3NH3Sn0.5Pb0.5I3 compare to
CH3NH3PbI3 corresponded to the larger Urbach energy E0 of CH3NH3Sn0.5Pb0.5I3.

Typical carrier transfer and recombination dynamics in Pb perovskite and Pb/Sn cocktail perovskite solar cells. The low efficiencyof Pb/Sn cocktail perovskite solar cell was found to be due to faster recombination between TiO2 and P3HT interface. This fasterrecombination could be suppressed by making pinhole-free perovskite layers.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

UEC hosts Japanese Neural Network Society Workshop on "Data-driven
approach for understanding cerebellar mechanisms on eye movement control"
Organizers Tadashi Yamazaki, University of Electro-Communications in Tokyo , and Akira Katoh, Tokai
University.
On 1 August 2015, a full day workshop on "data-driven approach for understanding cerebellar mechanisms oneye movement control" was held at UEC, Tokyo. The workshop was organized by Tadashi Yamazaki(assistant professor, UEC, Tokyo) and Akira Katoh (associate professor, Tokai University) and jointly
sponsored by the Japanese Neural Network Society (JNNS) and Brain Science Inspired Life Support ResearchCenter, UEC, Tokyo.
The workshop consisted of 10 speakers, most of whom were recently promoted to principle investigators attheir research institutes. In planning the workshop, the organizers endeavored to maintain a good balance of
speakers from Japan and overseas, and male and female representation. The final program consisted of three
speakers from the USA and the remainder from Japan, where four of the talks were given by female
participants. In spite of the combination of a highly technical program, the holiday season, and hot and humid
weather, more than 30 scientists participated in the workshop. The presentations and resulting heateddiscussions were held in English, and the workshop was successful in achieving its aims.
In cerebellar research, Marr (1969) and Albus (1970) proposed so-called "perceptron hypothesis" that regards
the cerebellum as a pattern recognition device via supervised learning. Ten years later, Ito et al. (1982)
discovered long-term depression, which was the memory mechanism within the cerebellum and was themissing piece of the Marr-Albus model.
Since then, the Marr-Albus-Ito model has influenced successive cerebellar research while acting as a compassthat points to the correct direction of research and way of thinking about the system. Hence, we often say,"cerebellar research is hypothesis driven".
However, where did the hypothesis come from? Of course, it came from data, specifically anatomical andmorphological data of cat's cerebellum obtained in the 1950s to 1960s. In those days, a very detailed wiring
diagram, or "blue print" of the cerebellum was already available. That is, detailed data allowed scientists tobuild a good hypothesis. In other words, "no data, no theory". Meanwhile, a data-driven approach has become
popular in brain research, where scientists try to extract latent meanings or relationships behind the massive
amounts of data. Therefore, in the workshop, we focused on "data".
The workshop included presentations on the cerebellum and eye movement control in primates. Recently, it
has been difficult to conduct primate research, so the participants had the privilege to see the latest anddetailed data in primate research. The data presented at the workshop ranged from microscopic level
The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

(molecular biology), mesoscopic level (electrophysiology) and macroscopic level (system / behavioral level),underscoring the very comprehensive nature of the workshop in covering research on cerebellum and eye
movement control.
Notably, Dr. Shinji Matsuda from UEC, Tokyo presented his technique to control long-term depression by
light. This technique will provide the final means to elucidate the causal relationship between long-term
depression and cerebellar motor learning.
In summary, the workshop was very successful. The organizers would like to have this kind of workshop on aregular basis to promote brain science at UEC, Tokyo and cerebellar research in Japan.
Finally, the organizers are grateful for the generous financial support from the following organizations:International Neuroinformatics Coordinating Facility (INCF) Japan Node Cerebellar Platform;
Comprehensive Brain Science Network; Tokai University Educational System General Research
Organization; and The University of Electro-Communications.

Further information
1. Workshop website: http://numericalbrain.org/jnnsjigen/index.en.html
2. Speakers and titles of talks
Kenichiro Miura (Kyoto Univ)
Visual control of eye movements in mice: the optokinetic response
Shuntaro Miki (Chubu Univ)
Cerebellar dependent predictive optokinetic response associated with oculomotor velocity storage mechanism
in goldfish, carp, zebrafish, medaka, and human
Naoko Inaba (Kyoto Univ)
The role of the cortical areas MT and MST in coding of visual motion during pursuit eye movements
Pablo M Blazquez (Washington Univ St. Louis)
Thinking inside the box. Signal processing by cerebellar cortex interneurons in the macaqueventralparaflocculus
Tatyana Yakusheva (Washington Univ St. Louis)
Role of GABAergic inhibition in the vestibular signal transformation carried out by the cerebellar nodulus anduvula
Aya Takemura (AIST)
Neural activity in monkey's cortical area MST Represents Retinal Error during Motor Learning
Yoshiko Kojima (Univ Washington)
Substantia nigra pars reticulata influences the error signals for the saccade adaptation
Shinji Matsuda (UEC, Tokyo)
Understanding and controlling synaptic plasticity

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Seiji Ono (Tsukuba Univ)
Role of visual velocity and position error signals in smooth pursuit adaptation
Yutaka Hirata (Chubu Univ)
Promoted motor learning of oculomotor velocity to position neural integrator under hyper-gravity and brighter
visual stimulation

Poster of the workshop

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UEC launches the Info-Powered Energy System Research Center (iPERC)
Susumu Morikura
UEC, University Research Administrator, Organization for Research Promotion
University of Electro-Communications, Tokyo (UEC, Tokyo) held asymposium to commemorate the launch of the Info-Powered Energy System
Research Center (iPERC) on 31st July, 2015. The iPERC was established to

President Fukuda, UEC

investigate and resolve global energy issues by nurturing human resources aspart of an inter industry-academia-government collaboration.
The symposium included talks by prominent scientists, educators, government
officials, and industrialists specializing in energy issues. More than 150 people
attended the symposium, including participants from other universities, industry
and government.
Takashi Fukuda, the President of UEC opened the symposium by welcoming

Keynote by President Tsuge,
Japan International Scienceand Technology Exchange
Centerthe participants and giving a brief overview of iPERC. Then, Nobuaki
Kawakami, the Director General, Science and Technology Policy Bureau,
MEXT, gave a congratulatory message. Ayao Tsuge, the President of the Japan
International Science and Technology Exchange Center, then gave a keynote
speech on Japan as an "Innovative Country driven by Sustainable Science andTechnology". Haruhisa Ichikawa, the Director of iPERC, gave a more detailed
description of the mission and plans of iPERC.

Prof. Ichikawa, Director of
iPERC

In the session for industry leaders, Takemitsu Kunio, senior vice president ofNEC, Tomiyasu Ichimura, senior director of Fujitsu Ltd, and Chiaki Itoh, vicepresident of Yokogawa Electric Corporation described their activities on theirenergy management businesses. These talks were very highly informative inunderstanding the current status of the energy business.
Finally, Seiichi Shin, vice director of iPERC gave concluding remarks on

Symposium speakers and UEC
executive board members

behalf of all the people associated with the symposium.
Following the success of this symposium, the directors of iPERC are planning to hold further meetings withassociated members to explore and promote advanced solutions in energy management.
Further information
Info-Powered Energy System Research Center (iPERC) website: http://www.iperc.uec.ac.jp/

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Delegates from Binghamton University, State University of New York, visit
UEC
UEC welcomed delegates from Binghamton University on 25-26 August 2015.
The visitors from Binghamton University, State University of New York(SUNY-B) were led by Distinguished Professor Krishnaswami Srihari, Dean of
the Thomas J. Watson School of Engineering and Applied Science and also
Executive Vice Provost for International Initiatives and Chief Global Affairs
Officer. The other members of the delegation were Professor Hiroki Sayama,

President Fukuda and Dean
Srihari exchanged greetings

Department of Systems Science and Industrial Engineering and Director of theCenter for Collective Dynamics of Complex Systems, and Ms. Amanda Chiarot,
International Alumni and Career Connections Coordinator of the Watson
School.
UEC and SUNY-B have had a collaborative agreement since 2014, and the visit
was arranged to identify specific areas of interaction including research,Three representatives from
Binghamton University

education, internships, and exchange of students and administrative staff.
The activities of SUNY-B were first introduced by Prof. Srihari to UEC faculty
members in English, and then in Japanese by Prof. Sayama to UEC students andfaculty members. SUNY-B, a prestigious university in U.S.A., is one of four
universities with doctoral degree courses at SUNY, which includes over sixty
higher education institutions including universities, colleges, academic medical
centers, and an online learning network.

Introduction of BU to UEC
students and faculty members

The main topics described by the two professors were: the location of theuniversity; number of students (undergraduate and graduate); student life on
campus; different entrance systems between Japan and U.S.A; and outstanding
research findings.
Prof. Kajimoto's Lab

The visit also included a tour of seven research groups at UEC, to give thevisitors first hand insights into research at UEC. The main research areas andpeople visited were: Virtual Reality and Interface (Prof. Kajimoto);
Info-Powered Energy (Prof. Ichikawa); Control Engineering and Security (Prof.
Sawada); Brain Science (Prof. Yokoi); Advanced Research Facilities (Prof.
Nozaki); Nano Electronics and Solar Cell (Prof. Shen); and Organic Synthesis

The meeting between UEC
and BU(Prof. Maki).
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Achievements made during the visit include (1) defining specific areas forpotential collaborative research; (2) clarification of specific organizations at both
universities to manage collaboration themes; (3) enhancement of mutual
understanding of student exchange programs offered by each university andsharing ideas to proceed with taking advantage of these programs; and (4)subjects such as international internship, collaboration on English language

UEC-KMITL GAL (Global
Alliance Lab)

education, and administrative staff exchange were positively discussed.
At the end of the visit, Dr. Kazushi Nakano, Member of the Board of Directors for Education at UEC, gave aclosing address. In his speech, Dr. Nakano touched on some global education programs being developed at
UEC and asked for possible cooperation from Binghamton University in the future.
In conclusion, the visit by the SUNY-B delegation was a huge success and very productive. As a matter of afact, UEC believes that the process of interacting with SUNY-B may serve as a model case in seeking
inter-university matching of research collaboration themes. UEC is grateful to the SUNY-B delegation for
visiting us and we look forward to a fruitful collaboration in the future.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Nanowire quantum dot solar cells: oxide layer boosts performance
Attempts to improve solar cells can seem a balancing act, as optimising one variable can compromise another.
The introduction of nanowires to colloidal quantum-dot solar cells (CQDSCs) aroused interest as a means ofimproving a limitation in the charge-collection layer thickness. However the high nanowire surface area
brings other inhibiting factors. Now Jin Chang, Qing Shen and colleagues demonstrate how a further
modification using an oxide layer can reduce the nanowire surface area effects for better-performing solar
cells.
Colloidal quantum dots offer a number of advantages for solar cells: they provide effective charge separation
layers for producing a photocurrent; have tunable band gaps; and can be solution-processed at low
temperatures. However the low diffusion length for charge carriers generated in colloidal quantum dots limits
the maximum layer thickness - it must be no thicker than the distance the carriers can travel to reach theheterojunction before recombining. This limited thickness caps the energy absorption capacity.
Penetrating the quantum-dot layers with nanowire heterojunctions can allow greater thicknesses. But since
recombination occurs at interfaces, the higher surface of nanowire heterojunctions undermines the advantage
made.
Chang, Shen and colleagues at the University of Electro-Communications and CREST in Japan, Universitat
Jaume I in Spain, Kyushu Institute of Technology and King Abdulaziz University in Saudi Arabia show that atitanium oxide layer can passivate the surface of the nanowires thereby reducing recombination. The oxide
layer allows a 40% improvement in the energy conversion efficiency of the devices and they are stable in airfor over 130 days.
"This work highlights the significance of metal oxide passivation in achieving high performance bulk
heterojunction solar cells," conclude the authors. "The charge recombination mechanism uncovered in thiswork could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells."
Reference
Jin Chang,*1,2 Yuki Kuga,a Iván Mora-Seró,3 Taro Toyoda,1,2 Yuhei Ogomi,4,2
Shuzi Hayase,4,2 Juan Bisquert3,5 and Qing Shen,*1,2 High reduction of interfacial charge recombination in
colloidal quantum dot solar cells by metal oxide surface passivation, Nanoscale, 7, 5446 (2015).
1. Faculty of Informatics and Engineering, The University of Electro-Communications,1-5-1 Chofugaoka, Chofu,
Tokyo 182-8585, Japan.
2. CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
3. Photovoltaic and Optoelectronic Devices Group, Department de Física, Universitat Jaume I, 12071 Castelló,
Spain
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4. Faculty of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino,
Wakamatsu-ku, Kitakyushu, Fukuoka 808-0196, Japan
5. Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia*corresponding author e-mail:jin@jupiter.pc.uec.ac.jp

shen@pc.uec.ac.jp(a) A schematic illustration of the solar cells with zinc oxide (ZnO) nanowire heterojunctions passivated withtitanium oxide (TiO2) and lead sulphide (PbS) colloidal-quantum-dot charge separation layers (ZnO@TiO2/PbS
solar cells);(b) a photograph of standard PbS CQDSCs fabricated in Shen's lab; (c) a typical cross-section scanningelectron microscope image of the ZnO@TiO2/PbS solar cells.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Motor behaviour: understanding the jerks that lurk in smooth movements
Apparently smooth continuous movements to trace moving objects harbour jerks. These jerks are absent when
there is no object to be traced and so are thought to stem from changes in motor instructions anticipated andfed forward by the brain to compensate for sensorimotor time lags. However so far there is no conclusive
evidence that this is the case. Now Yasuyuki Inoue and Yutaka Sakaguchi at the University ofElectro-communications have demonstrated a method for analysing apparently smooth movements that may
help to understand their jerky components.
"The true purpose of detecting discontinuities is to know when and how our brain divides a continuous motor
task into separate movement segments," explain Inoue and Sakaguchi in their report. While studies ofintermittency have been tackled using frequency analysis of the velocity profiles, the intervals between theintermittent motor discontinuities vary, so this may not be appropriate.
Another approach is to extract the sub-movements that comprise apparently continuous motion by identifying
the discontinuities. However the methods to do this - using kinematic parameters and curve fitting
optimisation - become unmanageable for long movements.
Inoue and Sakaguchi show that continuous wavelet transforms are an effective means of identifying
discontinuities without suffering the drawbacks of other approaches for longer movements. They also show
how to distinguish the discontinuities from other movement features such as hand tremors or peaks in a pulseof movement.
"Our method is essentially equivalent to detecting the jerk change points, but it uses both the amplitude andphase information of the complex wavelet transform to much improve detection performance," explain Inoueand Sakaguchi in their report. They successfully detected all the discontinuities in an artificial data set with nofalse detections, as well as demonstrating their approach on human subjects asked to trace a moving object
with their hand.
Reference
Inoue Y, Sakaguchi Y A wavelet-based method for extracting intermittent discontinuities observed in humanmotor behavior Neural Networks 62: 91-101 (2015)
doi:10.1016/j.neunet.2014.05.004

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Researchers at the University of Electro-Communications demonstrate their wavelet approach for discontinuity detectionin hand movements during the target tracking task.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

UEC students receive prestigious awards at international conference
Two UEC graduate students studying at the same laboratory wereawarded prizes for their presentations at the 23rd International
Conference on Nuclear Engineering, held in Chiba, Japan, 17-21 May
2015.
Naoki Miyano received the best poster prize (1) and Kazuhiro Kaiho
the best paper prize (2). Miyano and Kaiho are both master's degree
students at UEC's Department of Mechanical Engineering andIntelligent Systems studying under the supervision of Professor Tomio

Naoki Miyano (left) and Kazuhiro Kaiho
in the Okawa-Enoki lab at UEC.

Okawa.
Further information
Website of the 23rd International Conference on Nuclear Engineering, held in Chiba, Japan, 17-21 May
2015:http://www.icone23.org/about.html
Related technical publications
1. Kazuhiro Kaiho, Tomoyuki Kajihara, Tomio Okawa, 2015. Visualization of bubble nucleation process during
water subcooled flow boiling using a transparent heated surface, 23rd International Conference on Nuclear
Engineering, ICONE23-1121. [Best Paper Award]
2. Naoki Miyano, Tomio Okawa, Takafumi Suginaka, 2015. Study of bubble lift off from a vertical heated surface
in pool boiling, 23rd International Conference on Nuclear Engineering, ICONE22-1123. [Best Poster Award]
3. Tomio Okawa, Muhamad Zuhairi Bin Sulaiman, Daisuke Matsuo, 2014. Experimental study on the critical heat
flux and heat transfer coefficient in nanofluid pool boiling, 10th International Topical Meeting on Nuclear
Thermal Hydraulics, Operation and Safety, NUTHOS10- 1346.
4. Tomio Okawa, 2015. Enhancing Numerical Stability of a Two-Fluid Model by the Use of Interfacial Pressure
Terms, ASME Journal of Nuclear Engineering and Radiation Science, Vol. 1, Issue 2, 021001-11.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

A career in ultrashort pulse lasers, ultrafast spectroscopy, and quantum
information
Takayoshi Kobayashi Laboratory, Advanced Ultrafast Laser Research Center,
University of Electro-Communications, Tokyo.
Professor Takayoshi Kobayashi joined the University of Electro-Communications,Tokyo (UEC, Tokyo) as a Specially Appointed Professor after retiring from The
University of Tokyo in 2002. "Over my 49 year research career I have published about
580 original papers on a wide range of optical phenomena," says Kobayashi. "I evenbroke my own world record for generating sub- femtosecond laser pulses."
Indeed Kobayashi is one of the pioneers of using non-collinear optical parametric amplification (NOPA) to
produce ultrashort pulse lasers. In 1999 Kobayashi and colleagues set a world record by producing 4.7
femtosecond (fs) laser pulses in the 500-800 nm range after that Kobayashi kept breaking his own world
record from 1999 for more than 15 years. In 2011 Kobayashi broke his own world record by generating
carrier-envelope phase (CEP) stabilized 2.4 fs near infra-red pulses in the 410-820 nm wavelength range.
Such short pulses of intense laser light are important for investigating ultrafast and nonlinear optical propertiesof various condensed materials including polymers, optoelectronic device materials, and topological insulators.
Specific research being undertaken by Kobayashi and his colleagues includes: Real time, sub 5 femtosecond
spectroscopy of conducting polymer polyacetylenes and polydiacetlenes with highly optical nonlinear, andanother quasi-one-dimensional system of halogen-bridged mixed-valence metal complexes. Also important
study has been made for topological insulators which are recently attracting many researchers.
Other areas of research include quantum quantum photobiology, and femtosecond dynamics ofbacteriorhodopsin, a molecule that uses solar energy to generate energy by pumping protons across amembrane.
Another field of his research using nonlinear optical parametric interaction is a quantum information. This isalso a technique for ultrashort pulse generation. "Quantum entanglement is a fascinating area of research witha wide range of practical applications," says Kobayashi. "For example we are using so called entangled
photons to measure the spectrum of materials on the surface of the moon with the monochromator on earth.
These experiments can be carried out with a high sensitivity and low noise visible detector coupled with anoisy infra-red detector."
Recently, Kobayashi is doing research of development of super resolution optical microscopes, based on novel
ideas now being applied to several patents.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Kobayashi is also passionate about education and nurturing young scientists. "One of the rewarding things
about research is seeing how young scientists develop with time. It is highly rewarding to see students turninto quality scientists."
Further information
Takayoshi Kobayashi website: http://femto.pc.uec.ac.jp/index.html
References
Selection of ten papers out of about 580 original papers published by Takayoshi Kobayashi.
1. Sub-5-fs visible pulse generation by pulse-front-matched noncollinear optical parametric amplifier, A.
Shirakawa, I. Sakane, M. Takasaka, and T. Kobayashi, Appl. Phys. Lett. 74, 2268-2270, (1999).
2. Real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization: T. Kobayashi, T.
Saito, and H. Ohtani, Nature 414, 531-534(2001).
3. Controlling the carrier-envelope phase of ultrashort light pulses with opticalparametric amplifiers A.

Baltuska, T. Fuji, and T. Kobayashi, Phys. Rev. Lett. 88, 0133901, (2002).
4. Visible pulse compression to 4 fs by optical parametric amplification and programmable dispersion control,
Baltuska, T. Fuji, and T. Kobayashi, Opt. Lett. 27, 306-308, (2002).
5. Cascaded four-wave mixing and multicolored arrays generation in a sapphire plate by using two crossing
beams of femtosecond laser, J. Liu and T. Kobayashi, Opt. Exp. 16, 22119-22125, (2008).
6. Primary conformation change in bacteriorhodopsin on photoexcitation, A. Yabushita and T. Kobayashi, J.
Biophys. 96, 1447-1461, (2009).
7. Ultrafast Spectroscopy of oxy-hemoglobin during photodissociation, A. Yabushita and T. Kobayashi, J. Phys.
Chem. B, 114, 11654-11658, (2010).
8. Kinetic isotope effect on the proton-transfer in indigo carmine, I. Iwakura, A. Yabushita, and T. Kobayashi:
Chem. Phys. Lett. 484, 354-357(2010)
9. Temporal contrast enhancement of femtosecond pulses by a self-diffraction process in a Kerr bulk medium, J.
Liu, K. Okamura, Y. Kida, T. Teramoto, and T. Kobayashi, Opt. Exp. 18, 22245, (2010).
10. Octave-spanning carrier-envelope phase stabilized visible pulse with sub-3-fs pulse duration, K. Okamura andT. Kobayashi, Opt. Lett. 36,226-228, (2011).

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Experimental set up of ultrafast spectroscopy composed of NOPA, pulse compress system, and pulse formcharacterization system

Probe delay time dependence of difference transmission spectrum: The time-resolved spectrum at 201fs (= delay timeof probe pulse from the pump pulse introducing the change, which is probed by the probe, is different from that of
200fs.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Experimental set up for the application of "ghost image" to the measurement spectrum of distant materials
using quantum entangled photon pairs.

Measurement of spectrum of materials on the moon is possible in principle using the entangled photon pairwith a monochromator on the earth. Or Measurement of infrared spectrum can be performed using highsensitivity low noise visible detector using a noisy infrared detector.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

Result of absorption spectrum of distant materials using the entangled photon pairs.

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.

The University of Electro-Communications (UEC) in Tokyo
is a small, luminous university at the forefront of applied sciences, engineering, and technology
research. Its roots go back to the Technical Institute for Wireless Commutations, which wasestablished in 1918 by the Wireless Association to train so-called wireless engineers in maritime
communications in response to the Titanic disaster in 1912. In 1949, the UEC was established as anational university by the Japanese Ministry of Education, and moved in 1957 from Meguro to its
current Chofu campus Tokyo.
With approximately 4,000 students and 350 faculty, UEC is regarded as a small university, but withparticular expertise in wireless communications, laser science, robotics, informatics, and materialscience, to name just a few areas of research.
The UEC was selected for the Ministry of Education, Culture, Sports, Science and Technology (MEXT)
Program for Promoting the Enhancement of Research Universities as a result of its strengths in threemain areas: optics and photonics research, where we are number one for the number of joint
publications with foreign researchers; wireless communications, which reflects our roots; andmaterials-based research, particularly on fuel cells.
International Public Relations
The University of Electro-Communications
1-5-1 Chofugaoka, Chofu, Tokyo 182-8585
E-mail : kokusai-k@office.uec.ac.jp
Website : http://www.uec.ac.jp/eng/

The University of Electro-Communications 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585© 2015 The University of Electro-Communications.