New Color-Bearers of Keio's Faculty
of Science and Technology New Color-Bearers of Keio's Faculty
of Science and Technology

Developing Optical Microresonators to pave the way to realize Photonic Circuits

Perhaps you have been surprised by the heat when touching your notebook PC power adapter or the rear of a TV set. The fact is, electrical appliances, regardless of their functions, are releasing wasted heat as part of the electricity they consume.For example, even gold, which has excellent electrical conductivity, exhibits some resistance, not zero, and generates Joule heat responding to the resistance when electricity is passed. In other words,by simply passing a current the electric circuit loses heat energy proportional to its electrical resistance.
“Electronic circuits are bound to generate heat. But photonic circuits are totally different. Light, when passed through glass, causes no loss like Joule heat. Theoretically, photonic circuits work without loss,” explains Assistant Professor Takasumi Tanabe.
Capable of significantly reducing energy consumption compared with ordinary electronic circuits,expectations are high for photonic circuits as a solution to major issues facing our modern society,such as conservation of energy and reduction of CO₂ emissions.
With all advantages and no apparent shortcomings, but optical circuits actually come with their problems as well. One of them is the development of a device that can confine light in one place.Negatively charged electrons can be kept in place by taking advantage of the force of plus and minus attracting each other. But light does not have electric charges as electrons do. So we need to contrive an alternative method for stopping light in one place.
“An optical microresonator is known as a device to keep light in one place. The development of this particular device is essential for putting photonic circuits to practical use.If we can confine light in one place, then it will become possible to use this optical device as a memory. We can also use the same device as a switch or a transistor by manipulating the confined light. Among several approaches attempted in this study, I used photonic crystal technology to confine light and succeeded in running an logic circuit concerning computer memory.”

Having obtained positive results from a series of his studies, Dr. Tanabe took up the challenge of practical application of photonic circuits from this spring. His research theme is the development of an optical microresonator using silica,the main constituent of glass, as the raw material.
“There are several reasons for choosing silica as the raw material for my optical microresonator. First occurring to my mind was silica's high compatibility with existing optical devices. Silica is an attractive material from the application viewpoint.”
Devices required for a photonic circuit include the optical fiber cable and the planar lightwave circuit. Of these,passive devices such as those used for transmission of light signals and those for information branching are approaching the level of practical use. And many of these devices are silica-based. In short, if we succeed in developing an optical microresonator with silica, we can integrate into one chip such active devices as the optical memory, optical switch and optical transistor as well as existing passive devices, thus enabling an photonic integrated circuit to be created with ease.
Furthermore, silica, when compared with silicon which is the raw material often used for photonic crystals, has different characteristics such as smaller optical nonlinear coefficients and faster nonlinear transition speeds.By using silica, it is also possible to ascertain the influence that a difference in materials exercises on device functions.
Dr. Tanabe expressed his hopes saying, “The use of silica as the raw material enables us to re-examine,across the board, issues peculiar to the whole photonic integrated circuit including p eripheral equipment, rather than the optical microresonator as a single device.I think the results and issues identified in this process will go a long way to further photonic crystal and other photonic circuit studies.”

Shedding Light on Various “Whys”in Our Daily Lives

The Russula subnigricans, popularly known in Japan as “Nise Kurohatsu” (see photo below), looks truly tasty but is actually a poisonous mushroom. It was first announced as a mushroom of fatal toxicity during the 1950s. But it has almost been forgotten because no accidental deaths were reported during the ensuing 50 years and also because there are several other similar-looking mushrooms.
In July 2009 the British scientific magazine Nature Chemical Biology carried an article announcing that the poison in Russula subnigricans mushroom is cycloprop-2-ene carboxylic acid.
This achievement was the result of joint research with Dr. Kimiko Hashimoto (now Associate Professor at Kyoto Pharmaceutical University) as well as with Professor Masaya Nakata and Dr. Masanori Matsuura (then student) of the laboratory, to which Dr. Saikawa belongs. In the world of natural products investigation where almost all natural substances have been thoroughly investigated, this achievement has become a significant topic of conversation.

Cycloprop-2-ene carboxylic acid is a small substance – a ring consisting of three carbon atoms, to which carboxylic acid is attached. “Such a simple, small substance has long been left unidentified!” Dr. Saikawa talks about the surprise that struck her after years of investigation.
Although its molecular structure is simple, its extraction was far from easy. The investigative study began with identification of the Russula subnigricans mushroom. To evaluate the toxicity, the team adopted the method of injecting the toxic substance into the peritoneal cavity of mice. But before long it became known that mice would die even when non-toxic substance was injected. So the experiment had to be done anew by changing the policy to feed mice with the toxic substance.
The hardest problem encountered was that the toxic substance would disappear when an ordinary separation process was employed. Looking back over those days, Dr. Saikawa says, “We tried this way, and if it didn't work we didn't hesitate to take that way. In that sense, research scientists like us are quick-tempered.” The readiness to review and change research approaches as necessary and the toughness for devising and carrying out new solutions in rapid succession seem to be required. Finally, she found that the toxic substance disappeared due to concentration, which led to the improvement of the extraction process. Cycloprop-2-ene carboxylic acid was thus identified as the culprit for the Russula subnigricans mushroom after eight long years.

“It was hard and depressing when positive results were not in sight. But the moment its structure was known, everything became clear and I found all answers just before my eyes.” Once the structure of the toxic substance was identified, the question of the toxicity lost in the process of concentration was not a question at all. This excitingly fresh feeling derived from achievement seems to drive Dr. Saikawa into scientific pursuit. From this particular research project, she could also appreciate the joy of discovery of the natural world.
Discovery of new substances is also exciting as it allows her to pose new questions to other scientific fields. The greatest feature of this particular poison is that it causes “rhabdomyolysis” i n w h i ch mu s cl e s melt . Si nc e it s mechanism remains totally unknown, the achievement of her team is now a focus of attention within medical circles.

As a research scientist, Dr. Saikawa is about to launch a research theme on her own for the first time. In the past she frequented a zoo to sample hippopotamus sweat and climbed mountains many times in search of the targeted mushroom. From such experience she says, “Seeds of research themes are everywhere. But you can't find them if you're just sitting back watching TV or browsing through magazines. The only way is to use your own legs.” To find new research themes, she often goes out to sea as early as 4:00 in the morning with a fisherman with whom she recently befriended.

Creating Lossless Power Transmission Cables Using Iron-based High-Temperature Superconductive Material

In 1911 Heike Kamerlingh Onnes of the Netherlands discovered that electrical resistivity of mercury cooled to 4.2K (kelvin = the unit of absolute temperature, 0K being -273.15 °C) drops to zero. The temperature at which electrical resistivity becomes zero is known as the superconductivity transition temperature(Tc). Efforts in quest of materials that can become superconductive at higher temperatures have been made in the ensuing years.
“Just a century has passed since the discovery of superconductivity, during which time a number of superconductive materials have been identified. These materials are roughly divided into metalbased compounds and cuprate-based ones. In terms of transition temperature, 39K for MgB₂ discovered in 2001 is the highest of metal-based compounds while high-temperature superconductivity at 135K for a cuprate-based material was confirmed in 1993. After that no significant discoveries had been reported,” Dr. Kamihara outlines the development of superconductivity. Amid the stagnancy in the exploration of superconductive materials, Dr. Kamihara and co-workers (his bosses & a student) presented an original paper in 2008. The key point of the paper was the confirmation of superconductivity occurring in a compound containing iron, which overthrew the conventional view that iron, responsible for magnetism, is not suitable for superconductive materials. The paper was soon followed by a Chinese researcher reporting high-temperature superconductivity at 55 K, together leading to the discovery of the third type of high-Tc superconductive material.
“The superconductive material we found this time was an iron-based fourelement compound. This combination of elements has great potential for applicat ion to ot her mater ia ls in addition to iron. I heard of a positive evaluation that the number of candidate combinations has increased dramatically. It also came to be known that its single crystal is in the shape of a thin plate and that electric current flows in the longitudinal direction through the single crystal thin plate. The establishment of an electric cable processing technology taking advantage of the single crystal's structure is said to be the key to practical application of the superconductor.”
The paper surprised and intrigued numerous researchers and became No. 1 in the world in 2008 in the number of citations of theses written in English. In 2009, Dr. Kamihara was honored with the 13th Superconductivity Science and Technology Prize.

Much is expected of superconductivity for application to many fields such as linear motor, electric power transmission and strong magnetic field generation. Above all, you can safely say the field of application on which the greatest hope is placed is the electric cable made of a superconductive material with zero electrical resistance. Given zero electrical resistance, it is theoretically possible to create electric cables without transmission loss – the ultimate cable that does not waste energy at all during transmission.
“In reality, however, I must admit that there are many problems. Even if we successfully identified an excellent material with a high transition temperature and elucidated its structure, heaps of problems would have to be solved before using the material in electric cables. For example, since an iron-based superconductive material is ceramics made up of small single crystals ranging in size from 1 to 100 micrometers, you cannot process it by stretching or melting like a metal. In order to form a long electric cable, heretofore unknown technologies need to be developed, such as a processing technology capable of orderly arranging the small single crystals, and a technology to prevent the junction between crystals from becoming oxidized, for example. What's more, how should protective coating for the cable be, and how should the cable be connected to the electrode? All such problems must be cleared.”
While Dr. Kamihara began to address studies to put superconductivity into practical use, his inquisitive spirit is also directed to exploration into the fourth type of superconductive materials beyond iron-based ones. We'd like to see the fruition of his new challenge.

MC : Ms. Saikawa, you studied at Harvard Medical School. What idea or feelings did you have when attending Harvard? And how did Keio look like when seen from out there?
Saikawa : Ever since I first joined Keio as an undergraduate, I’d had no chance to study overseas – engaging for years in similar research themes at the same laboratory. Harvard Medical School is literally a “medical graduate school.” As a person with little experience in traveling abroad, studying abroad itself was a challenge. So were the medical and biomedical fields that would be involved. Getting out of my laboratory appeared like a rare experience. “I will see and experience as many new things as I can” . . . this was the feeling I had before flying to the United States.
I got this opportunity thanks to our department’s system that allows one young researcher to study abroad every year. Because of this system, I came to feel like studying overseas. It proved to be a truly precious opportunity for me since it would have been difficult to do so on my own.
Once settled there, I was greatly impressed with Harvard in some aspects. I generally found the students enjoying their own campus lives while studying hard at the same time – a major similarity with Keio. When people asked me where I was from, quite a few of them knew the name of Keio. I got the impression that Keio was well known globally.
If asked about my specialty, I am a person of chemistry rather than medicine. Not all researchers in the medical field are knowledgeable about chemistry, and vice versa. On occasion I saw chemistry still being held in high esteem in the world of medicine. Chemistry is a very old field of science whereas biology is gaining in popularity as of late. But I got the impression that chemistry is still a worthwhile pursuit.
MC : Importance of chemistry has been recognized again because you went to Harvard Medical School, you mean?
Saikawa : Maybe so. Discussions often become hot and mutually aggressive when talking with persons from medicine. It seems we talk at cross-purposes as the other party never sees problems from the perspective of chemical structure. But if we communicated thoroughly, both parties would come to understand and say, “Oh, I didn’t know about such a perspective.” In this way I could learn many new perspectives and approaches, which was a valuable experience.
Kamihara : Did you join any laboratory?
Saikawa : Yes, I did.
Kamihara : Does the medical school conduct clinical studies? Are there patients?
Saikawa : Some engage in clinical studies. But there are some Harvard hospitals in the adjacent area, so most of the clinically oriented engage in laboratory work there. Neurological studies are also conducted there. Patients never walk around in the area.
MC : And you came across some who knew the name of Keio, didn’t you?
Saikawa : Keio’s name was relatively well known at the medical school, which surprised me. When I was an undergraduate at Keio, I belonged to the Kendo Japanese Fencing Club, and this club had an alliance with Harvard. Presumably Keio is trying to approach Harvard. I could see similarities in school cultures as private colleges – the unrestricted atmosphere and so on. So I could feel at home at Harvard.
Tanabe : Keio’s Kendo Club in alliance with Harvard? Really?
Saikawa : Harvard students practicing kendo join Keio’s training camp.
Tanabe : You mean the Kendo Club . . . one of Keio’s sports clubs?
Saikawa : Right.
Tanabe : Great!

MC : From your viewpoints as teachers, what do Keio students look like?
Kamihara : I don’t know much about the students yet because I graduated from Keio five years ago and have just returned as an assistant professor. If Keio has not changed much from back then, I can say Keio students are good at helping each other. As Mr. Tanabe put it just a while ago, generally they are self-motivated, have a high ability for basic learning, and have latitude in seeing things. Students with mental latitude are helping each other in a friendly way. It may be safe to say this is the Keio culture. From my own experience as a dull student, I can say there is at least one bright student nearby. If you respect, target or copy that student, you can attain significant growth. In this respect, Keio offers an ideal environment.
MC : Do you see any drawbacks?
Kamihara : Given such latitude, no good results could be produced if they tune in with less motivated students. Once they have entered Keio, it depends on if the students can make the most of this university to their advantage.
MC : How do you think, Mr. Tanabe?
Tanabe : It may be repetitious but I’d like to emphasize the key word, good or bad, is latitude – or diversity in the routes of entry.
MC : Ms. Saikawa, what do you think?
Saikawa : Regarding “latitude,” a variety of paths are made available at Keio. I also have the impression that Keio is intent to foster latitude of students’ individuality. Though I know little about other universities, Keio appears tolerant to almost anything students do – instead of fostering specialists from the beginning. In the worst case this attitude may lead them nowhere, but there are actually those students who maintain an unexpected combination of totally different interests, some saying “I like computation and organic chemistry at the same time.” And such students advance and join laboratories without losing interest.
I know studying in laboratories inevitably requires specialized knowledge, but I’m doing my best so that they won’t lose their multi-faceted interests. It’s interesting to find gaps in them – unexpected gaps between their academic pursuits and their special abilities. It seems students who have been within Keio since childhood have been educated so as not to lose such individuality.
Tanabe : That’s very important. I agree. In the field of science, one needs to focus on one particular thing. But engineers bring in two seemingly unrelated things and combine them to create something new.
Saikawa : Yes, combining things ingeniously is a wonder.
Tanabe : Indeed. And the key to success is to think of a combination beyond everyone’s imagination. For example, back when the laser was first invented, nobody ever imagined it could be applied to medical treatment. But the new field of laser treatment was created by combining laser with medical treatment. The farther away fields are apart from each other conceptually, the more fantastic the result of combination.
Saikawa : In my observation, Keio students seem to be educated to be able to conceive things in an unrestricted manner.
MC : But their interests may possibly become too dispersed to go anywhere. What do you think?
Saikawa : Well, some of our students appear unmanageably voracious for interests. In the worst case, this can prevent them from focusing on what’s really important. This also holds true when it comes to circle activities. Many are accustomed to pursue circle activities and research work at the same time. They are prone to easily poke their nose into what looks interesting. If things go smoothly, you can say they know how to get on in life. But if things don’t go well, everything they do may fail. Generally speaking, however, they are good at doing that way. So accustomed to such a way of life during college days, they are generally good at making it in the world after graduation. Being not top-heavy but knowledgeable about many things seems to enable them to enjoy doing things throughout their lives.

MC : Now please tell us why you set your mind on science or chose your careers as researchers.
Tanabe: As a junior high student I saw an NHK Special TV program entitled “The Autobiography of Japan as an Electronics-based Nation.” It was an account of Japan having striven as an electronics-based nation, introducing the transistor and other developments. So impressed by the program, I wanted to do something like that in the future.
Kamihara : Since childhood, I haven’t been a type with special abilities. So, like most of the friends around me, I thought I would enter a university and find employment with a company. Looking at my school report card, I found myself rather weak at English . . . but math and science records were acceptable, which encouraged me to go on to a university. Because my father was a high school teacher, I wanted to follow suit. So, upon graduation, I took an entrance exam for Tokyo Gakugei University – the result was a total failure. During one year of preparing for the next chance, I frequented the home of my high school physics teacher when he recommended several physics-oriented introductory books like an introduction to the theory of relativity, which intrigued me. Then I was admitted into the present department of a university the following year. Since then to date I have simply focused on challenges just before my eyes, going along the stream of things. I’m not a type with great ambition.
Tanabe : So was my case. I was so weak at the Japanese language that I had to choose the science course in college.
Kamihara : Ancient Japanese literature was interesting as far as its content, but I never became inclined to memorize what was written. After having escaped from all my weaknesses, I now find myself working in this course.
MC : Both of you left strong fields after having eliminated weak fields, right?
Kamihara : Well, to be exact, it’s a field where I could be “competitive” with others, rather than a “strong” field.
Saikawa : To tell you the truth, I used to definitely be a liberal arts type student. I loved and was good at subjects like the Japanese language and music. I didn’t like math and science so much. At home we often ate mountain vegetables. They might have been roadside grass. My eyes gradually opened to plants and the world of nature as I referred to an illustrated book of flora as to their classification and to check whether they were edible or not. I liked doing so and it was a necessity of life.
In the autumn of high school sophomore year, I had to choose which course to take, liberal arts or science. By that time, I was not so good at the Japanese language. I particularly disliked the ambiguity associated with questions like “Describe the author’s thought or feelings.” The teacher would give me an NG (X) mark to my answer but I couldn’t understand why. Conversely, subjects such as chemistry and biology appealed to me as they used clear-cut approaches like “The constituents of this plant are so and so.” So I suddenly decided to change my course from liberal arts to science. It was the catalyst for shifting my career to this side.
I seem to be an inquisitive type by nature, asking myself “What is this plant?”, “What constituents is this made of?”, “Is this edible?”, “When does this plant grow?” and other questions. But basically I’m a liberal arts type person in the way of thinking. This sometimes makes me regret my course change when I talk with persons who have come straight through scientific pursuit.
MC : Well, each one of you has his or her own individuality. With these teachers credited with outstanding achievements, we’re sure your students can foster hopes for a bright future. Thank you very much for your time and precious remarks. Newly arriving at your posts or just returning from overseas study, you must be highly motivated. We sincerely hope your research activities will develop greatly and produce superb results.