薄膜および微細構造におけるGHz-THz 音響波伝播のイメージング

抄録

  Ultrashort light pulses absorbed in a medium generate both bulk and surface acoustic waves: we focus here on imaging the surface waves and on monitoring the bulk acoustic waves that propagate in the depth direction. This is done in the time domain by delayed probe light pulses. For the bulk acoustic waves, the generated frequency ranges up to 1 THz. Some studies concerning the ultrafast electron-phonon relaxation in metal films, high frequency generation in semiconductor quantum wells, and high frequency shear acoustic wave generation and detection are reviewed here. For the surface acoustic waves the generated frequency ranges up to 1 GHz, and time-resolved two-dimensional images of the propagation are obtained with micron lateral spatial resolution. This imaging method is applied to anisotropic crystals and phononic crystals to elucidate their acoustic properties.