Apparatus for broadband, time-resolved measurements of laser-induced reflectivity transients with sub-10 fs resolution

• Broadband pump-probe setup with sub-10 fs time resolution for reflectivity studies. • Cascaded hollow-core fiber post compression for generating few-cycle probe pulses. • Spectrally resolved transient reflectivity studies under variable laser excitation. • Precise zero-delay calibration via sum-frequency cross-correlation implemented. • Reflectivity dynamics of gold above ablation threshold measured and modeled. The interaction of ultrashort laser pulses with materials enables precise surface processing and has been in the focus of research due to its scientific and technological significance. While the fundamental processes of energy deposition, internal energy transfer, and material response are not yet fully understood, advances in experimental techniques have provided valuable insights into these phenomena. Here, we introduce an advanced optical broadband pump-probe setup for transient reflectivity measurements with sub–10 fs time resolution. The excitation takes place at 780 nm with a pulse length of 80 fs and variable fluence. We use broadband, few-cycle pulses for probing the material response which is crucial for gaining deeper insights into the early-time dynamics of light matter interaction and thus contribute to further understanding of the involved physical processes. We present measurements on bulk gold above the modification threshold benchmarking the performance of the setup. The behavior of gold under femtosecond irradiation is theoretically modelled and compared with the measurement results.