| 研究実績の概要 |
Our group is specialized in acoustic metamaterials and ultrafast phononics from audio to GHz frequencies. In particular, we have experience in picosecond ultrasonics and plasmonics in nanostructures, plasphonics, acoustic metamaterials, surface acoustic wave visualization with ultrashort optical pulses, ultrafast electronic and thermal diffusion, and nanoscale phonon detection using atomic force microscopy.
Research highlights have been as follows. First demonstration of: 1) surface acoustic wave real time imaging on solids, 2) interferometic detection of ultrafast surface motion of solids, 3) surface wave real time imaging on phononic crystals, 4) picosecond echo detection on semicondutor quantum wells, 5) picosecond shear phonon pulse detection in solids, 6) picosecond tracking of phonon pulses in nanostructures, 7) giant extraordinary transmission of acoustic waves in zero-mass metamaterials, 8) realisation of efficient air-to-water acoustic transmission, and demonstration of extraordinary transmission bulk longitudinal waves in solids.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
1. Metamaterial-based acoustic microscopy: We have constructed scanning extraordinary-transmission-based acoustic microscopes for deep sub-wavelength imaging consisting of a loudspeaker placed in a tapered tube closed with a polyethylene tensioned membrane of diameter 1 cm. We have made test images for two types of object, a cm-sized wooden cross and a cm-sized rubber pad, at the resonance frequency of 1340 Hz.
2. Metasurface for air-water acoustic transmission: We have fabricated and measured an efficient metasurface from masses and springs over an area of 15 cm x15 cm, allowing enhanced transmission from water to air or from solid to air. So far we have tested the case of transmission from acrylic to air, and demonstrated that the principle works as expected
3. Metapillars and metaplates for broadband multimode vibration isolation: Simulations and experiments in single-material metabeam and metarods have been carried out and the principle of a perfect-bandgap metabeam (rectangular cross-section) and metarod demonstrated
4. Flexural metaplates: We have simulated metaplates with square- or triangular-lattice spirally-arranged slits and discovered both negative refraction and phonon focusing for both in-plane shear and symmetric plate (Lamb) waves with prism and block samples at GHz frequencies.
5. Phoxonic metamaterials for new physics and applications: As a first step we have designed a new two-dimensional GHz acoustic metasurface which should have single negative acoustic metamaterial properties and plasmonic/photonic crystal properties simultaneously.
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| 今後の研究の推進方策 |
1. Metamaterial-based acoustic microscopy: We will conduct deep sub-wavelength imaging at higher frequencies up to the ~MHz range, for application to fabrics at first. We will attempt to demonstrate in-solid extraordinary acoustic transmission with 3D-printed arrays of rods connecting larger-diameter rods.
2. Metasurface for air-water acoustic transmission: We shall experiment on the fabrication of a water-air acoustic metasurface, and explore sensor applications of our air-solid version.
3. Metapillars and metaplates for broadband multimode vibration isolation: We shall fabricate, model and optimize rubber-made versions with ~10 Hz low-frequency blocking abilities. Multiple-resonator-frequency wide-band versions will be designed.
4. Flexural metaplates: We will focus on metaplates that work with symmetric Lamb waves that show negative refraction. We will fabricate and model 10 kHz-1 GHz structures in the form of blocks and prisms, and image their single- or double-negative (DNG) metamaterial behaviour in the frequency or time domains with optical techniques, characterizing their acoustic dispersion.
5. Phoxonic metamaterials for new physics and applications: We will use of a plasmonic/photonic crystal together with a 2D GHz acoustic metamaterial at first and experiment with designs in the em microwave range.
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