Could you please let us know more about your research on nano-photonics?

The purpose of our research in nano-photonics is to realize high performance material that can be applied in the field of optics and photonics, utilizing the characteristics of nano-structures constructed using nanotechnology. For example, we are researching the technology that controls the process by which light is generated by LEDs (light emitting diodes) and LDs (laser diodes) with an accuracy rate of one photon, the minimum unit of light. Because it is very difficult to manipulate one photon due to the dimness of its light, we use the atom as the minimum unit of measurement. If we consider the phenomenon that the electron orbit of an atom allows only two electrons in the same state of energy, then the control of the photon becomes possible. Because the number of entering electrons is limited to only two, we are putting in only two electrons and putting out photons one by one. However, because the atom is also too small and controlling it is very difficult, the semiconductor quantum dot is used instead.

The semiconductor quantum dot has a similar function to the atom and is called an “artificial atom”, even though it includes tens of thousands of atoms. As forming only one semiconductor quantum dot is difficult, we take out a single quantum dot by the micro-fabrication that uses nanotechnology, and research the process of generation and absorption of photons.

 

 

How did you get involved in this research?

I have been researching the new possibilities of semiconductor-related optical applications such as LEDs and LDs. At first, the luminescence wavelengths of LEDs and LDs were limited to about 800 nm, that from the GaAs system, but they have subsequently extended to red, blue, and ultraviolet, as well as longer wavelengths. We have been researching for a long time, and we discovered shorter wavelengths with the materials having wide gaps, such as zinc oxides, and reduced longer wavelengths by adding nitrogen to compound semiconductors, such as GaAs. The new Nanotechnology Research Center was built at the Research Institute of Electronic Science, Hokkaido University, in 2003, and I was engaged in the establishment of a clean room, and then moved here.

Many microfabrication systems were installed in the new clean room, including SAMCO systems. I wanted to utilize this opportunity and broaden my research field into “Nano” a little more. I moved from the optical materials research field to the optical nano high-performance materials research field, and began my current research. I’m researching LED and the photon source of light that controls and emits one photon. The reason for my focus is that research in the field of quantum information processing and telecommunications has grown a great deal in the past five years.

It is necessary to take the photon out of the communications field; to see it work, we transmit information by putting the information on 1 photon, because the photon is the minimum unit, and is indivisible. It is said that communication using photons can be safe. Therefore, quantum code communication that uses the photon becomes considerably more prevalent, and various proof experiments are conducted. However, the source of light is still in its early stages. As I thought that the single photon source, like the LD in the current optic fiber communication field, might contribute greatly to the quantum code communication field, I started my current research.

 

Could you introduce to the strategic creation research creation of the superconducting photonics and the application of the science and technology promotion mechanism that started in 2005?

I think that the topic of superconducting photonics might be unfamiliar to many people. Recent research in the field of quantum information processing, such as quantum computers has become considerably more prevalent, as well as quantum telecommunications using the photon. Especially, quantum information processing that uses superconductivity seems promising, because it enables easy integration and extendibility. This field is actively researched worldwide. However, there has not been any connection of superconducting with the photonics field, though superconducting has been used by a power application and the current medical treatment application, etc.

I think that the interfacing technique that ties communication using the photon and quantum information processing by superconducting will be needed in the future, when the quantum information on superconducting is transported. To develop this field, I proposed the concept of superconducting photonics and am researching it. Currently, I’m trying to extract the photons from a superconducting state, while we have such technology only in microwave, which has a much larger wavelength.

In the superconducting state, electrons are forming pairs, and I’m trying to inject the pair of electrons into the semiconductor and get them to emit light, which is the interface between superconducting and photonics. It is confirmed that the pair of electrons can put out the photon three times as fast as an electron does, and that the luminescence can be one digit stronger.

 

 

What kind of processes are you doing using SAMCO systems?

The Nanotech Center was completed in 2003. We purchased a SAMCO CVD system, ICP etching system and RIE system from SAMCO. Here, a series of micro-fabrication processes, from micro patterns with electron beam through the insulation film deposition and etching, can be achieved. We use the SAMCO systems for making nano-scale structures, quantum dots and diode structure.

Moreover, as a feature of Hokkaido University, these systems are operated in an open facility and can be used not only by the university staff and faculty, but also by other researchers and scientists. Furthermore, some people travel from Tokyo and West Japan to use the SAMCO systems. They are widely and effectively used in an open-to-all research facility.

 

 

Do you have any comments or suggestions for SAMCO?

I think the progress of our research depends on micro-fabrication technology. I would like SAMCO to further pursue this technology and I expect SAMCO to develop and provide us with new systems in the future.