Faculty of Engineering


Find a field you like and study it “step by step”

In this issue of “Tell Us Teacher,” we talked to Dr. Tadayuki Imai, who specializes in the development of light-controlling components and materials for use in printers, projectors, and various other applications.

Q:Please tell me what your field of research is.

At the Department of Mechanical and Electrical System Engineering in the KUAS Faculty of Engineering, I am researching optical control devices, optical crystals, dielectrics and holography.

Q:First of all, what made you go to into engineering?

I have been interested in making things since I was a child, showing interest in Sunday carpentry programs on TV and reading an electronics book that I bought when I was in the third grade of elementary school over and over. I used to go to the electric street in Teramachi-dori, Kyoto, to buy parts and had fun building various electronic devices, but I could never understand how electronic circuits worked. I am a step-by-step sort of person, and it was a pity that I could not find a book with a satisfactory explanation at that time. Because of this, I decided in elementary school that I would go on to study engineering at university in order to solve this mystery. I wanted to be an engineer and design electronic circuitry in the future. When I entered university, my longstanding mystery was solved, but in the end, I did not become a circuit engineer.

Q:You started full-fledged research in graduate school?

I started my research when I was in graduate school, which was 30 years ago. In graduate school, I was doing research on making thin films of ferroelectric crystals with the aim of applying them to electronic components such as sensors. Many of you may not have heard of ferroelectrics, but they are similar to magnets. Magnets create a magnetic field around them, attracting iron and other materials, but ferroelectrics are an electric version of this, creating an electric field around them. I’m sure everyone knows that static electricity attracts hair to a plastic sheet, but that is also because an electric field is created around the plastic sheet. Ferroelectrics are similar to this, but a little stronger. Ferroelectrics are most commonly used as a material for electrical components called capacitors. They are used in almost all appliances that use electricity, and they say there are several hundred of them in a single smartphone.

Developing components and devices that control light.

Q:After completing the first half of graduate school, you entered a corporate research institute, right?

After completing the first two years of my graduate studies, I was assigned to a corporate research institute. To tell the truth, the ferroelectric thin films that I had been working on in graduate school did not suit me very well, so I wanted to shift my specialty a little. The research theme given to me by the company was the optical application of ferroelectrics. Since the materials were the same, I thought it would be a similar field, but it turned out to be quite different. Thin films, as the name implies, are films so thin that they are less than 1/100th the thickness of a hair and can only be seen with an electron microscope, etc. The research I started at the company was on the same line of materials, but dealt with masses that were thousands or tens of thousands of times larger than the films and were normally visible to the eye. These are called bulk single crystals, as distinguished from thin films. This single crystal has an unusual property in that its refractive index changes with electricity. This is called the electrooptic (EO) effect. The term “refractive index” may not be used very often, but I think it is a word that comes up at least once in high school science classes. When you dip a straight stick in a glass of water, the stick will look bent. This is because the refractive index of air and water is different, and light is bent (refracted) at the boundary between the two. The EO effect is usually used in optical communications, and I applied it to the development of devices that use light to record information on single crystals, and to research and develop components that control the direction in which light travels. Although I was involved in slightly different research during some periods of my career, I have continued my research and development in the field of optical applications of these single crystals.

Q:What is your current research?

Currently, I am focusing on single crystal materials in which the EO effect occurs. I mentioned that the EO effect can change the refractive index with electricity. This means that the angle of refraction of light can be electrically changed. In other words, the direction of light rays can be controlled. In reality, however, the amount of change in the refractive index due to the phenomenon is very small, and the direction of the light rays cannot be visibly changed. However, a crystalline material called KTN single crystal (*) has a large amount of refractive index change and the light direction can be visibly changed. This has led to the development of a topographical surveying system and is used for tunnel construction. The material is also applied to lenses that can change their focus. In addition, we are aiming to find materials that can change the refractive index by more than orders of magnitude, so that they can be used in light-based shows such as projection mapping.

*An oxide crystal composed of potassium (K), tantalum (Ta), and niobium (Nb).


Creating crystals that look like gemstones is also fun.

Q:Is there anything in particular that you would like to emphasize in your research?

Bulk single crystals, which are used to manipulate light, are often clear and glittery. In fact, many gems, such as diamonds, emeralds, and sapphires, are single crystals too. I also do research on making single crystals, and when a good single crystal is produced, I am fascinated by how beautiful it looks. When I was young, I often dreamed of producing such amazingly beautiful single crystals. In reality, it is very difficult to produce such a single crystal, which is another reason why researchers are fascinated by them. It seems that research on light is not very interesting to many people, and I was the same way when I was a student. However, the objects that deal with light are sparkling and beautiful. I hope that many students will take an interest in this field, as there is such a benefit.

Q:In the future, how would you like contribute to society through your research?

Devices (components) that change the direction of light rays are used in many areas. Shows that use laser beams are an easy-to-understand example, but devices like those are also used as a component for projectors used in projection mapping. There is also a type of printer called a laser printer, in which these components are also used. There are also various types of 3D printers, some of which use light for modeling. We are currently working on materials that can change their refractive index, and we hope to increase their capabilities by an order of magnitude and bring about innovations in these fields. Refractive index is also a factor that determines the “visibility” of an object. Why can we see a glass cup even though it is transparent? It is because the refractive index of glass is different from that of air. Why does a diamond sparkle? Partly because of the way it is cut, but also because of its high refractive index. I believe that if we can create materials that can freely change their refractive index, we will be able to create visual expressions that are unimaginable using today’s computer displays.

Q:The KUAS Graduate School of Engineering welcomed its first class of students in 2020. What is your message to those students?

There are many students with unique characteristics in our inaugural class, and the teachers are greatly inspired by this. The personalities of the students vary, but I hope that all of them will quickly find something they like. If you like something, you can devote yourself to it and become good at it.

Q:Tell us about your hobbies and interests, and what you were into when you were a student.

Currently, I don’t have any very “hobby-like” hobbies. When I was a university student, I wanted to do something a little different from engineering, so I joined a club called the Archaeology Society, where we investigated history through science. During summer and spring vacations, I stayed in the Tango region (the northern part of Kyoto) to investigate archaeological sites. I also had a part-time job excavating ruins. My engineering knowledge came in handy when I was surveying ancient tombs and ruins in a village, and drawing from the data. Even now, I sometimes go to see the ruins. I sometimes wonder if I could contribute to archaeology by providing new methods for measuring ruins and relics with light, even if it would be quite a challenge to do so.

Learn more about Dr. Tadayuki Imai