Waseda University · Engineering
Professor Akihiko Hirata's research lab specializes in the atomic-scale characterization of amorphous and metallic glass materials, with a focus on understanding local atomic structures such as icosahedral order and geometric frustration. The lab employs advanced electron microscopy techniques—particularly angstrom-beam electron diffraction—combined with synchrotron X-ray scattering and computer simulations to probe the disordered structures of functional amorphous materials like silicon monoxide. In parallel, the lab explores photonic wireless communication systems using millimeter-wave technologies, emphasizing high-power, photonic-based mmWave signal generation and transmission. Their work bridges fundamental materials science with applied photonics, aiming to resolve long-standing structural mysteries in non-crystalline materials and develop next-generation communication technologies.
Figures are computed from collected data and may differ slightly.
Icosahedral order has been suggested as the prevalent atomic motif of supercooled liquids and metallic glasses for more than half a century, because the icosahedron is highly close-packed but is difficult to grow, owing to structure frustration and the lack of translational periodicity. By means of angstrom-beam electron diffraction of single icosahedra, we report experimental observation of local icosahedral order in metallic glasses. All the detected icosahedra were found to be distorted with
We present a wireless link system that uses millimeter-wave (MMW) photonic techniques. The photonic transmitter in the wireless link consists of an optical 120-GHz MMW generator, an optical modulator, and a high-power photonic MMW emitter. A uni-traveling carrier photodiode (UTC-PD) was used as the photonic emitter in order to eliminate electronic MMW amplifiers. We evaluated the dependence of UTC-PD output power on its transit-time limited bandwidth and its CR-time constant limited bandwidth, a
Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous s
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