All-optical in-depth detection of the acoustic wave emitted by a single gold nanorod

Feng Xu (1, 2) , Yannick Guillet (1) , Serge Ravaine (3) , Bertrand Audoin (1)

1 I2M - Institut de Mécanique et d'Ingénierie de Bordeaux
2 WHUT - Wuhan University of Technology
3 CRPP - Centre de Recherche Paul Pascal

Asingle gold nanorod dropped on the surface of a silica substrate is used as a transient optoacoustic source of gigahertz hypersounds.We demonstrate the all-optical detection of the as-generated acousticwave front propagating in the silica substrate. For this purpose, time-resolved femtosecond pump-probe experiments are performed in a reflection configuration. The fundamental breathing mode of the nanorod is detected at 23 GHz by interferometry, and the longitudinal acousticwave radiated in the silica substrate is detected by time-resolved Brillouin scattering. By tuning the optical probe wavelength from 750 to 900 nm, hypersounds with wavelengths of 260–315 nm are detected in the silica substrate, with corresponding acoustic frequencies in the range of 19–23 GHz. To confirm the origin of these hypersounds, we theoretically analyze the influence of the acoustic excitation spectrum on the temporal envelope of the transient reflectivity. This analysis proves that the acoustic wave detected in the silica substrate results from the excitation of the breathing mode of the nanorod. These results pave the way for performing local in-depth elastic nanoscopy.

Domaines: Matériaux; Optique [physics.optics]

Feng Xu, Yannick Guillet, Serge Ravaine, Bertrand Audoin. All-optical in-depth detection of the acoustic wave emitted by a single gold nanorod. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 97 (16), ⟨10.1103/PhysRevB.97.165412⟩. ⟨hal-01764556⟩