ABSTRACT Picosecond acoustic (PA) pulses emitted by emerging ultrafast photoacoustic transducers of 2D layered semiconductors process unique advantages in noninvasive detection and imaging applications due to strong penetration ability and nanometer‐scale spatial resolution. Here, we realize bidirectional emission of PA pulses in a sandwiched 2D semiconductor heterostructures, PMMA//, using femtosecond pump‐probe. By constructing an interference model and performing quantitative spectral analysis, we spatiotemporally decouple emitted PA pulses signals. This allows us to simultaneously observe modulus inhomogeneity and obtain attenuation coefficients of emitted PA pulses in both PMMA and BaF 2 . Mechanical coupling quality difference of both van der Waals heterointerfaces surrounding the layers has been observed and further elucidated through theoretical calculation of 1D elastic equation. Our results open up a new avenue to ultrafast photoacousic study in complicated heterostructures containing 2D layered semiconductors.
Wang et al. (2026) studied this question.