Fig. 3. Temporal characterization of the oscillatory modes’ propagation.

(A) CWT of the oscillatory component of the ΔT/T signal at three different distances (333, 555, and 777 nm) from the center of the pump region and measured at a fluence of ≃1.6 mJ/cm². The color map represents the magnitude of the CWT. The white dotted lines approximately mark the location of the strongest phonon oscillations. The periodic oscillations in the CWT are clearly resolved, and their possible origins are discussed in the main text. (B) Time delay of the region of strong oscillations as a function of the ring distance. The orange dashed line represents the linear fit of the data in the region outside the pump area and has an inverse slope of 1.51 × 10⁵ m/s.