Optical tracking of picosecond coherent phonon pulse focusing inside a sub-micron object

Thomas Dehoux, Kenichi Ishikawa, Paul H. Otsuka, Motonobu Tomoda, Osamu Matsuda, Masazumi Fujiwara, Shigeki Takeuchi, Istvan A. Veres, Vitalyi E. Gusev, Oliver B. Wright

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


By means of an ultrafast optical technique, we track focused gigahertz coherent phonon pulses in objects down to sub-micron in size. Infrared light pulses illuminating the surface of a single metal-coated silica fibre generate longitudinal-phonon wave packets. Reflection of visible probe light pulses from the fibre surface allows the vibrational modes of the fibre to be detected, and Brillouin optical scattering of partially transmitted light pulses allows the acoustic wavefronts inside the transparent fibre to be continuously monitored. We thereby probe acoustic focusing in the time domain resulting from generation at the curved fibre surface. An analytical model, supported by three-dimensional simulations, suggests that we have followed the focusing of the acoustic beam down to a ~ 150-nm diameter waist inside the fibre. This work significantly narrows the lateral resolution for focusing of picosecond acoustic pulses, normally limited by the diffraction limit of focused optical pulses to ~ 1 μm, and thereby opens up a new range of possibilities including nanoscale acoustic microscopy and nanoscale computed tomography.

Original languageEnglish
Article numbere16082
JournalLight: Science and Applications
Issue number5
Publication statusPublished - May 2016
Externally publishedYes


  • Acoustic-optic
  • Fibre
  • Optical scattering
  • Picosecond
  • Ultrasonics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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