
A career in researching light began with a 'Really?!' moment.
The Photonic Device Engineering Lab, the Department of Electronic Engineering at the Graduate School of Engineering, Tohoku University, is headed by Professor Kyoko Kitamura who first arrived at this university in September 2023. The word “photonic” in the lab’s name refers to “light.” Professor Kitamura mainly studies structures called photonic crystals, and she is engaged in the research and development of such structures from both the science and engineering perspectives. First successfully created in the world in 2000 by Japanese researchers, photonic crystals are artificial structures made of regularly arranged semiconductor nanostructures in a sequence of several hundred nanometers (one billionth of a meter) which is the same as the wavelength of light. A photonic crystal has a property of not permitting light of a certain frequency range to penetrate. By deftly designing a frequency range which does not permit light to penetrate (a photonic band gap) or by introducing an intentional disturbance (a structural defect) into the regular structure of a crystal, it is possible to control light at will, which leads to possible applications in optical circuit devices such as optical storage and optical switches, and in quantum information processing and communication such as quantum computers.
A graduate of Kyoto University’s Undergraduate School of Chemical Science and Technology, one of Professor Kitamura’s options for graduate school was to specialize in a field related to semiconductor fabrication. What led her to a career in optical device research was something she once heard during a lecture. She learned that if you periodically make holes in a semiconductor, you can manipulate light at will. She recalls, “I learned that you can freely control light just by making patterns on a semiconductor substrate using an electron beam and creating nano-level holes with plasma. I honestly thought, ‘How can that be?! There’s no way that’s possible!’ That was my first encounter with photonic crystals, and I thought if that was truly possible, then it would be fascinating, so I decided to study it.”
The lecturer at the time was Professor Susumu Noda of Kyoto University’s Department of Electronic Science and Engineering who later became her mentor. Professor Kitamura focused her research on photonic crystals at Professor Noda’s lab and after she received her doctorate degree, she moved her research base to the Faculty of Electrical Engineering and Electronics of the Kyoto Institute of Technology, developing technology for designing laser beams using photonic crystals, among other things.