Realtime correction of probe pulse in subpicosecond time-resolved transient absorption spectroscopy

Abstract

Due to its breakthrough the electro-optical time response limitation for picosecond dynamics of processes, many research groups around the world operating in different fields from physics and chemistry to biology, medicine and material science, utilize laser setups capable of providing subpicosecond pulses and femtosecond-level time delay lines. However the signal amount of Femto-picosecond Dynamics is about at an altitude of 1%, but the fluctuation of femtosecond probe pulse at its best can only reach about 5%. Real-time correct the probe pulse is the only effective way to realize subpicosecond time-resolved detection precision of transient absorption spectroscopy. So in this paper, reference pulse was drawn into the measurement equipment through different methods to dispel the fluctuation of probe pulse. Firstly, in the case of Subpicosecond time-resolved transient absorption spectroscopy, probe and reference beams have the same spectral distribution and derived from the same source to measure the variation of transmittance in the excited volume. Secondly probe pulse is spatially and temporally overlapped to the excitation pulse, reference pulse spatially overlapped but temporally anticipated in respect to the excitation pulse. Finally reference pulse passes through the sample in a different position. The detector can be a CCD camera or a double photodiode. The results shown that when reference pulse passes through the sample in a different position and detected by CCD, the correction results can reach to 1%. Which meet the femto-picosecond dynamics precise requirement.