The 29-cm−1 ruby phonon detector as a probe for ultrashort strain solitons

We demonstrate the interaction between ultrashort acoustic strain solitons and the 29-cm−1 electronic two-level systems in photoexcited ruby. For propagation along the crystallographic c-axis we observe a strong soliton-induced electronic population only after reflection at the far end of the crystal. We attribute this to mode-conversion and diffuse scattering at the crystal surface, which breaks the inhibited coupling of the soliton travelling along the c-axis. Model calculations show good agreement assuming a hemispherical scattering source and dipolar form for the interaction strength.