Small Atomic Displacements Recorded in Bismuth by the Optical Reflectivity of Femtosecond Laser-Pulse Excitations

Davide Boschetto (1) , E.G. Gamaly (2) , A.V. Rode (2) , B. Luther-Davies (2) , D. Glijer (1) , T. Garl (1) , O. Albert (1) , Antoine Rousse (1) , Jean Etchepare (1)

1 LOA - Laboratoire d'optique appliquée
2 LPC - Laser Physics Centre

Subtle atomic motion in a Bi crystal excited by a 35 fs-laser pulse has been recovered from the transient reflectivity of an optical probe measured with an accuracy of 10^-5. Analysis shows that a novel effect reported here—an initial negative drop in reflectivity—relates to a delicate coherent displacement of atoms by the polarization force during the pulse. We also show that reflectivity oscillations with a frequency coinciding with that of cold Bi are related to optical phonons excited by the electron temperature gradient through electron-phonon coupling.

Domains: Optics [physics.optics]

Davide Boschetto, E.G. Gamaly, A.V. Rode, B. Luther-Davies, D. Glijer, et al.. Small Atomic Displacements Recorded in Bismuth by the Optical Reflectivity of Femtosecond Laser-Pulse Excitations. Physical Review Letters, 2008, 100 (2), pp.027404. ⟨10.1103/PhysRevLett.100.027404⟩. ⟨hal-00515651⟩