2019年第80回応用物理学会秋季学術講演会

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合同セッションM 「フォノンエンジニアリング」 » 22.1 合同セッションM 「フォノンエンジニアリング」

[18a-E214-1~5] 22.1 合同セッションM 「フォノンエンジニアリング」

2019年9月18日(水) 10:00 〜 11:45 E214 (E214)

野村 政宏(東大)

10:00 〜 10:30

[18a-E214-1] Two-dimensional Imaging of Zero-Group-Velocity Lamb Waves

Oliver B. Wright1、Qingnan Xie2、Sylvain Mezil1、Paul H. Otsuka1、Motonobu Tomoda1、Jerome Laurent3、Zhonghua Chen2、Osamu Matsuda1 (1.Hokkaido Univ.、2.Nanjing Univ. S&T、3.Institut Langevin)

キーワード:acoustics, photonics, ultrafast

Waveguides channel propagating waves with reduced losses thanks to the confined dimensions, and are widely used in optics and acoustics. They are dispersive, i.e., the phase and the group velocities differ. Zero-group-velocity (ZGV) modes are particular points in a dispersion relation where the group velocity vanishes whereas the phase velocity remains finite. These modes can be found in most waveguide geometries (e.g., fibres and cylinders) and have the advantages of combining reduced losses and high Q factor. Here we present the imaging of gigahertz zero-group velocity acoustic waves in a microscopic plate. Lamb waves in a bilayer consisting of a ~2 micron thickness silicon nitride plate coated with polycrystalline titanium are imaged by means of a time-resolved two-dimensional imaging technique using an ultrashort-pulse laser. We identify and isolate the first ZGV mode, its associated Q factor and its lifetime. Applications include nanoscale non-destructive testing and extension to imaging photonic ZGV in two dimensions.