Dual-grating single-shot pump-probe technique

A simple and effective single-shot pump-probe technique is reported for studying ultrafast dynamic processes in various materials. Using only two commercial gratings, a large time window of ∼95.58 ps is spatially encoded in a single probe pulse, and single-shot time-resolved measurements are implemented. The time window in this single-shot pump-probe technique exceeds the maximum values in those reported works using the echelon or angle beam encoding strategy. The phase difference difficulty in the echelon encoding strategies is also overcome in our method, where a customized echelon is not necessary. The ultrafast dynamic processes of ZnSe and indolium squaraine (ISQ) at a wavelength of 650 nm were investigated using this technique for validation. The single-shot dynamics of ZnSe show an ultrafast two-photon absorption process followed by a weaker slow-recovery carrier absorption process. In the ISQ, a strong ground-state bleaching process is also observed. The transmittance of ISQ increases significantly after impulsive light excitation and maintains a slow increase until a time delay of ∼80 ps, which can be attributed to the transition from the S_n state to the S₁ state. In addition, a comparison with the previously reported single-shot pump-probe technique highlights the advantages of our technique.