Dai-Sik Kim

The scientific community is sincerely mourning the loss of Dai-Sik Kim, a pioneer in the field of terahertz and nanophotonics research. He was a passionate explorer and a true scientist who set a great milestone in the development and direction of science and technology in this area. Through pioneering research for over 30 years, Kim deeply reshaped our understanding of light–matter interactions at the nanoscale and made critical advances in science and technology in a wide range of topics, from laser-based ultrafast optics to quantum optics.

Kim served as distinguished professor and the founding director of the Quantum Photonics Institute at the Ulsan Institute of Science and Technology (UNIST) in South Korea, not only proving excellence in nanoscience but also making great contributions to mentoring students and reconsidering the international status of the Korean scientific community.

Kim began his scientific journey at the University of California, Berkeley, earning a doctorate under the supervision of Peter Y. Yu. His early work on femtosecond Raman scattering in III/V semiconductors was groundbreaking. He used advanced laser technology to provide unprecedented insights into hot electron cooling and intervalley scattering processes in semiconductors, adding depth to existing understanding of hot electron effects. This paved the way for postdoctoral research at Oklahoma State University and Bell Labs and broadened the boundaries of quantum well research and semiconductor nonlinearity. His meticulous studies of coherent dynamics of excitons in GaAs/AlGaAs quantum wells (together with Jagdeep Shah) were instrumental in developing ultrafast coherent spectroscopy of semiconductors and have provided fundamental insight in many-body effects governing their nonlinear optical response, demonstrating his remarkable experimental skills.

Returning to Korea, Kim joined Seoul National University and started by studying the physical properties of various materials using ultrafast lasers, and he expanded his research focus to surface plasmon polariton (SPP) nanostructures. Inspired by Ebbesen’s work on plasmonic arrays, Kim made essential contributions to the foundations of SPP research by using advanced nanofabrication methods for creating novel plasmonic devices. He initiated a highly successful partnership with researchers from the Max-Born-Institute in Germany and successfully investigated plasmonic near-fields in nano-hole and nano-slit arrays. This led to the observation and control of the extraordinary transmission of light through such arrays. His studies on the transmission of few-cycle optical pulses through nano-slit arrays, performed in the framework of this collaboration, are a pioneering contribution to the field of ultrafast nano-optics. These achievements facilitated collaborative partnerships with researchers in Germany and around the world, marking the beginning of continuous and impactful knowledge expansion and innovation. He went on to develop a groundbreaking way to control light transmission and field enhancement at the nanoscale through cooperation with the Max-Born-Institute in Berlin and the University of Oldenburg, supported by the Korean government’s Global Research Lab program.

Using nanoscale hole structures and near-field optics, Kim succeeded in separately mapping the vector components of electric fields near the nano-structures that could not be seen by conventional far-field measurements. He always challenged the fundamental limits of nature and did not hesitate to create new questions: What is the smallest hole size that light can pass through? To overcome the dimension mismatch between nano-sized holes and a long wavelength of light, he took on a new challenge. In 2008, at Seoul National University, he succeeded in interacting with terahertz waves and nano-slits for the first time and achieved a strong field enhancement and confinement near the slit. Since its first success, this concept has been widely used to enhance light to induce nonlinearity or to promote related research, and it led to the keyword “Tera-Nano.”

Through his relocation from Seoul National University to UNIST, Kim led major interdisciplinary efforts directed toward the practical use of the terahertz technology as well as toward increasing the scientific depth of the research even further. His research team at the Quantum Photonics Institute has made remarkable advances in nano technology and achieved atomic-scale dimensional control that can lead to breakthroughs in terahertz spectroscopy, nonlinear metamaterials, and ultrasensitive detectors. Kim’s invention, which uses flexible substrates to realize adjustable nanogap resonators, was particularly influential to both scientific and industrial applications by providing a new level of control over strong electromagnetic fields. His recent work on the angstrom-scale terahertz nanogap technology, which can create a zero-dimensional gap (zerogap), demonstrates his relentless efforts to break scientific boundaries, inspiring many current researchers in Korea and beyond.

In addition to his contributions to our scientific understanding, Kim also served as a dedicated mentor in guiding more than 30 PhD students who currently hold prominent positions in academia and industry. Unafraid of new challenges, his frontier spirit, passion, and his unique kindness aroused the students’ curiosity and gave them the courage to move into a new world. He always encouraged students to challenge conventions and not to hesitate to make innovative discoveries. His influence has expanded to the wider scientific community, contributing greatly to the development of the new field of nano-optics and nanotechnology, by organizing international conferences where world-class scholars gather. He was recognized for his efforts and achievements by receiving numerous prestigious awards, including the Korea Science Award and the 2024 Humboldt Research Award for invigorating Korean–German collaborations in nano-optics.

The core driving force of his constant strive for excellence and nonstop research over decades undoubtedly relied on his unique courage: Dai-Sik was never afraid of entering uncharted paths and surpassing barriers toward new learning. His passing leaves a profound void in the scientific community around the world, but his legacy will continue to inspire the next generation of researchers in the fields of nanophotonics and terahertz science.

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