Showcase on Researchfrom the Laboratory

Breakthroughs in Photonics ICT
The forefront of Nano ICT research−Utilizing the world s most advanced ultra-microfabrication andnanophotonic device technologies to create ultrafast,high-sensitivity, low-power consuming, innovative optical ICT coretechnology that surpasses the limitations of current silicon devices−

Left / Shin-ichiro Inoue, Ph.D. (Engineering) Senior Researcher, Nano ICT Laboratory, Advanced ICT Research Institute
Right / Shigehito Miki, Ph.D. (Engineering) Senior Researcher, Nano ICT Laboratory, Advanced ICT Research Institute

Here at the Nano ICT Laboratory, Advanced ICT
Research Institute, we are conducting research thataims to establish innovative optical control technology that enhances optical modulation speed, optical detection eﬃciency, and power consumption
performance to levels diﬃcult to reach with existing
technology by taking advantage of superior organic
material with optical-electronic capabilities, superconducting materials, and nanostructured unique
optical-electronic device capabilities in order tocontrol environmental load and, at the same time,realize high eﬃciency and speed of informationcommunications.
Now let s take a look at leading-edge researchin Organic Nano ICT and Single-Photon Detection Technology.

＊1 Silicon Photonics
Technology that integrates diﬀering functions in various optical devices on a single
silicon chip. It has superior integration and can realize mass production and low-costof components by diverting from existing CMOS processes.

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Holding the Key toOvercoming Limitations
Nanophotonic Devices
Researcher: Shin-ichiro Inoue■ Integration of ultrafast nanophotonic devices througha hybrid of organic material and silicon photonics＊1
In the midst of huge expansion and diversification of
information-communications networks exemplified in recent years
by cloud computing and smartphones, information-communication
volume is expected to rapidly increase, leading to an explosive risein network device power consumption. Conventional electronic
router systems and silicon CMOS technology＊2 are already reaching
their physical limits in order to meet the conflicting performance
demands of both accelerating information-communications speedvolume and energy-conservation requests from society. To addressthese problems, it is essential that we make a fundamental shift
away from traditional electrical signal processing towards
optical signal processing.
＊2 CMOS (Complementary Metal Oxide Semiconductor) Technology
A silicon LSI chip fabrication technology that uses CMOS, a standard semiconductor
structure.

As information processing becomes more optical, not only
thermal and processing-speed issues will be resolved, but also
power consumption can be drastically reduced. However,
optics has properties such as diﬀraction limits and little interaction between materials, and with existing technology, sizes
in electronic components will become much larger. In orderto realize genuine integrated optical circuits such as on-chip
ultrafast optical communications, a critical challenge is how
to realize optical devices on an extremely small scale similar
to electronic devices. For this, the key to further rapid progress in future information-communications is research in
nanophotonic devices that enable optical conﬁnement andcontrol in micro-sized spaces. At the Nano ICT Laboratory,
we believe that the integration of organic materials andsilicon photonics will lead to revolutionary breakthroughs in
optical integration and optical signal processing, and we areundertaking research on unique nanophotonic devices. To
advance optical information processing, development of technology that integrates electronic integrated circuits withsuperior complex signal processing performance and optical
integrated circuits with exceptional high-speeds and energyconservation is indispensible, particularly important being
the integration of an electrooptic (EO) modulator that converts electronic signals to optical signals. In conventional
optical modulators that use lithium niobate (LN) and silicon,
optical modulation speeds are limited to approximately
40GHz, but with the use of organic EO polymer, ultrafast
optical modulation speeds above 100GHz are possible. Moreover, it has a much larger EO coeﬃcient than those of LN,
which enables low-voltage devices. Conversely, we once
thought that organic material was not suitable for integration
due to its small refraction index. However, light can be conﬁned in the nanoregion by realizing a silicon-hybrid structure
because organic material can combine with various types ofother materials. Therefore, by integrating the advantages ofboth silicon photonics and organic material technologies, we
believe that the integration of ultrafast optical control devices
can be realized for the ﬁrst time.

Organic-silicon
hybrid nanophotonic
devicemakes signiﬁcant low-power consumption feasible. Combining
these technologies is expected to minimize the size of electronic and optical devices and enable the development of ultimately ultrafast integrated optical/electronic circuits that
replace bottlenecked parts of electronic integrated circuits ona single chip with optics.

■ Building Nano-Optical Devices Establishment ofprocessing technology and process development
In order to realize the ultimate nano-optical device, hybridization of technology and development of extremely highprecision, ultraﬁne processing technology on a nano-orderscale are essential. However, organic material diﬀers fromsemiconductor material in that microfabrication processes
have not been established and many issues such as processing damage and control of polar orientation of chromophores
in the nanoregion make it diﬃcult to be processed. Opticaldevice theoretical calculation processes are also very criticalfactors. We proceed with a layout of the optical device structure by 3-dimensionally designing various device structure
models and testing and analyzing the actual device characteristics in a computed simulation. The important point here isthat we have to replicate with high-accuracy the organic/Sihybrid optical device structure designed on a nano-orderscale within the actual microfabrication process.
To overcome these technical problems, a cleanroom environment is essential where the entire process can be done
consistently, including material development, nano-processing,and evaluation. NICT is the only research group worldwide
comprehensively advancing research from this type oforganic material development to nanophotonic device
production/evaluation, expanding highly characteristic
research as it strengthens both technologies and facilities.

●Cleanroom■ Future Prospects●Schematic diagram of an EO optical integrated chip and electron
micrograph of a silicon-integrated nanophotonic component

The nanophotonic structure also enables the creation ofterminable optical states called slow light where optical
speeds are artiﬁcially decelerated to approximately 1/100. This
uses a periodic structure of the order of light wavelength
called photonic crystal, and, by using the slow light eﬀect,
the Nonlinear Optical Eﬀects of materials are substantiallyenhanced. Thus, it further reduces optical device size andMore than 60 years have passed since the technology
changed from vacuum tubes to transistors. It is possible in
the next 10 years that, like the revolutionary development ofelectronic computers, a fundamental change in informationcommunications technology will occur due to a shift fromelectronic to optical chips along with the new silicon photonics trend. At the Nano ICT Laboratory, making the integrationof silicon photonics and organic materials our keyword, we are
realizing low-power consumption, integration, and ultra-highspeeds in optical modulation devices, and moreover, working
towards solving important issues focused on the application of
long-term durable, reliable organic nanophotonic devices,taking advantage of the strength of having a research lab environment where the entire process is consistent, from material
development to device production/evaluation.

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Hybrid devices of organic materials and silicon photonics use
the optical functionality of organic material and allow development towards unprecedented, new optics technologies such as
all-optical switches, optical buffers, and ultrasensitive biologicalsensors. Integrating the mutual advantages of both organic optical functionality and nanophotonic device technology is expected
to make great contributions in a wide range of optical ICT fields
such as next-generation ultrafast optical communications above
hundreds of Gbps, high-capacity green ICT, and advanced optical sensing networks.

Shin-ichiro Inoue

Senior Researcher, Nano ICT Laboratory,
Advanced ICT Research InstituteP r o fil e

A f te r c o m p l e t i n g a d o c to r a l c o u r s e a t To k yo I n s t i t u te ofTechnology and serving as RIKEN (The Institute of Physical andChemical Research), Special Postdoctoral Researcher andAssistant Professor, Institute for Materials Chemistr y andEngineering, Kyushu University, Inoue joined NICT in April 2010.
He is engaged in research and development in optical electronics,
nano-microfabrication, organic nonlinear optics, andnanophotonic devices. He holds a concurrent position as
Associate Professor, Graduate School of Engineering Faculty andEngineering, Kobe University. He has received many awards
i n c l u d i n g t h e Te j i m a D o c to r a l D i s s e r t a t i o n Awa rd, Fu n a i
Information Technology Promotion Award, Ando Incentive Prize for
the Study of Electronics, The 3rd RIKEN FRS Promotion Award,
and Research Award by Research Foundation for Opto-Scienceand Technology. When not immersing himself in work, he enjoys
spending time with his children.
R e m a r kfEstablishing Next-Generation Photon
Detection Technology inSuperconductive Device Research
Researcher: Shigehito Miki

■ Detecting single photons with superconducting
material exhibiting unique physical properties [SSPD]
Superconducting materials exhibit unique physical properties
not shown in other materials such as perfect conductivity, perfectdiamagnetism, and flux quantization. At the Nano ICT Laboratory, research and development is being conducted on various
sophisticated devices using these physical properties. The factthat superconducting devices must be cooled to ultra low temperatures is often seen as a drawback, but because ultra low temperature environments can minimize thermal noise to an
extremely small scale, it is the best for producing ultrasensitive“detectors” otherwise impossible with other materials. In particular, the superconducting nanowire single-photon detector system(SSPD) is currently gaining attention from various research
fields such as quantum information communications as a technology that provides much higher performance compared to the
traditionally used avalanche photodiode (APD).
The electrical resistance of superconductors becomes zero
below superconducting critical temperature (Tc), however whena single photon enters, the superconductive state is destroyed
locally. It is essential that the superconductor is processed into
the nanowire in order to generate electric resistance caused by
the breakdown of this local superconductive state and detect
single photons with high-sensitivity. Moreover, in order to cause
photon incidence efficiently onto the ultra nanowire, arranging
the nanowire in a meandering shape and enlarging the lightreceiving area are also necessary.

■ Creating Superconductive Nanowire
in a Cleanroom
As previously mentioned, in order to efficiently detect photons, you must produce narrow and long superconductive nanowire. At the Nano ICT Laboratory, we are developing superconducting devices in the Advanced ICT Research Institute’s cleanroom laboratories equipped with the world’ s most advanced
technology in terms of niobium nitride—single crystal thin film
deposition technology. With this film-formation technology,r o m R e s e a r c h e rNanophotonic device and optical/electronic fusion technology not
o n l y c o n t r i b u t e s to l o w - p o w e r c o n s u m p t i o n a n d f a s t e r
information-communications networks but also enables flexibility
and diversified applicability of optics, and by spreading to all
information equipment and advanced technology, from within LSI
c h i p s to b i o c h i p s, i t h o l d s th e p ote nti a l fo r revo l u ti o n a r y
break throughs in our ever-expanding advanced informationsociety. Pursuing a wide range of fundamental research from nanoand bio ICT to brain information, the Advanced ICT ResearchInstitute utilizes the characteristics unique to micro-sized,
high-per formance, flexible organic nanophotonic devices tocontinue contributing to new technological innovations in
information communications from ultrafast, extremely-low-power
consuming optical integrated devices to the realization of
bio-optical chip integration.

●Superconducting niobium nitride ﬁlm-generating instrument in acleanroom

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NICT NEWS NOV. 2012

we can produce NbN film that can demonstrate superconductivity
even in 4-nanometer-thick film compsed of several atomic layers.
Furthermore, using ultra-microfabrication technology that utilizes
electron beam lithography systems and etching equipment, wehave achieved fabricating nanowire of approximately 100 nanometers in width and realized SSPD devices. At this time, the total
distance of one nanowire within a SSPD component is almost
20,000 times that of the nanowire width, extending up to 2 millimeters. The entire SSPD component fabrication process can bedone inside a cleanroom using various tuned and constructed
instrumentation, and therefore, test production of devices withnew structures and optimized device designs can be rapidly performed.

Shigehito Miki

Senior Researcher, Nano ICT Laboratory,
Advanced ICT Research InstituteP r o f

●SSPD diagram■ Further Advancement of Photon Detector
Performance
Beginning in 2006, SSPD research and development at NICT
brought about a cooling system for SSPD in 2008 and succeededin capturing a value of approximately 1-2% in system detection
efficiency at a communication wavelength band (1550nm). At
this stage, it is still a low detection efficiency compared with therival component, APD, however, when we considered its characteristics such as the overwhelmingly low dark count and comprehensively evaluated it, we showed that SSPD has substantial
advantages. Moreover, thanks to later structural revisions, detection efficiency reached over 20% mid-2010 and showed just by
this efficiency rate that it exceeded APD values. Here at the Nano
ICT Laboratory, we aim to make large contributions to the development of future information-communications technology byrealizing single-photon detectors with ultimate performance thatcan respond to the needs of various fields including quantum
information-communication technology.

il eAfter completing a doctoral course at Graduate School, Kobe
University and serving as a researcher of Basic Research Program(CREST) at the Japan Science and Technology Agency, Miki joined
NICT in October 20 05. As a student, he belonged to acollaborative course between Kobe University and NICT and sincethen has been engaged in superconductivity at the Advanced ICT
Re se arch Institute, f irst as a traine e. He re ce ived the 146
Committee award, Japan Society for the Promotion of Science,
encouragement award for outstanding lecture, Japan Society ofApplied Physics, The Best Paper Award of Superconducting
Division, Japan Society of Applied Physics, as well as The Young
Scientists’ Prize of the Commendation for Science and Technology
by the Minister of Education, Culture, Spor ts, Science andTechnology. No matter how busy, he values spending time with hisfamily on days of f and enjoys visiting many dif ferent places
together.
R e m a r k

fr o m R e s e a r c h e rWith the aim to create new information-communication devicet e c h n o l o g y, w e a r e c o n d u c t i n g f u n d a m e n t a l
optical-electromagnetic-quantum devices that use superconductivity
circuit technology research, superconductive-optical interface
research-development, and applied research forquantum-information communications/ultrafast photonic networks.
High-speed, highly-sensitive photon detection technology is a
critical component in various research fields including quantum
information-communications technology, and photon detectors
u s i n g s u p e rc o n d u c t i v i t y h a v e a d v a n t a g e s i n w i d e b a n d ,high-sensitivity, and speed that outdo existing semiconductor
photon detectors. We are conducting research and development on
superconducting nanowire single-proton detectors system (SSPD) in
order to realize proton detectors whose ultimate performanceexceeds the limits of conventional photon detectors.

NICT NEWS NOV. 20126