Foundation of Nanophotonics

    Motoichi Ohtsu’s contributions in nanophotonics have gained him an international reputation. He is the pioneer of nanophotonics. He and his collaborators invented a selective chemical-etching method of fabricating high-resolution fiber probes for optical near-field generation. Soon after this work, he founded “nanophotonics” in 1993. Nanophotonics utilizes the local electromagnetic interaction between nanometric matter via an optical near-field in a macroscopic heat bath. To analyze this interaction, he and his collaborators pioneered a quantum optical theory based on the concept of dressed photon exchange. Based on this theory, he has invented a variety of innovative devices, fabrications, and systems.

    He and his collaborators developed a near-field photoemission spectrometer using a fiber probe in the ultraviolet-infrared region for diagnosing single semiconductor quantum dots, etc. Applying this methodology, they developed a sliding head for high-density/high-speed write/read in an optical disc memory system. Based on this, he directed a Japanese national project and succeeded in realizing storage density of 1 Tb/inch2. Using the virtual exciton-polariton theory, he invented a variety of innovative nanophotonic devices that are operated by near field-optical energy transfer and subsequent relaxation between optically forbidden exciton states in quantum dots, including a switch, logic gates, and an optical nanofountain. In addition, the group developed chemical vapor deposition and lithography techniques and succeeded in depositing nanometric material and carving nanometric patterns. Essentially, they discovered a nonadiabatic process in a photochemical reaction. That is, by using an optical near-field with low photon energy (visible light), metal-organic vapor molecules are dissociated and organic photo-resist thin films are exposed. Theoretically, they analyzed this phenomenon as violating the Franck-Condon principle precisely. Based on these works, they claimed that large, expensive ultraviolet light sources are no longer required for optical nanofabrication. He also founded “atom-photonics”, which manipulates neutral atoms in a vacuum using an optical near-field. His pioneering works are based on the theoretical analysis of virtual exciton-polariton theory, the guidance of neutral atoms through a hollow optical fiber, atom-detecting devices, atom-detectors, and an atomic funnel. For these works, he utilized his academic background involving intensive research in the fields of laser frequency control and optical frequency comb generation. More recently, he and his collaborators have developed innovative architectures for optical signal transmission systems by assembling nanophotonic devices. They have also developed novel secure optical storage systems by utilizing the hierarchy of near-field optical interactions.

    In short, Motoichi Ohtsu founded nanophotonics and has devoted his work to establishing this novel theory and creating devices, fabrications, and systems that utilize the unique near-field optical interaction between nanometric materials. His essential contribution is not only breaking the diffraction limit of light but also that he has realized innovative optical science and technology that would be impossible using conventional propagating light.

    For his outstanding works, he won the outstanding achievement award from the Institute of Electronics, Information and Communication Engineers, Japan, in 2007.


[1] M. Ohtsu, T. Kawazoe, T. Yatsui, and M. Naruse、Nanophotonics: Application of Dressed Photons to Novel Photonic Devices and Systems、2008、IEEE J. Selected Topics in Quantum Electron., vol.14, no.6, pp.1404-1417
[2] M. Ohtsu and K. Kobayashi、Optical Near Fields、2003、Springer-Verag, Berlin
[3] M. Ohtsu, K. Kobayashi, T. Kawazoe, T. Yatsui, and M. Naruse、Principles of Nanophotonics、2008、CRC Press, Boca Raton

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