Ultra-Stabilization Detection in Femtosecond Time Resolution Transient Absorption System from a Tight-Focusing Filamentation

Abstract

Femtosecond time resolution transient absorption spectroscopy (FTRTAS) is one of the most powerful tools to obtain ultrafast photoexcitation dynamics of matter. The rapid development of photosensitive materials such as bioprotein and advanced photoelectric thin films put forward higher stability requirements for the technique of FTRTAS. In this paper, we proposed a strategy to establish a tight-focusing stable femtosecond laser filamentation system to optimize the stability of probe pulses, and finally achieve highly sensitive detection of weak signals. It is demonstrated that tight focusing lens can effectively reduce the self-focusing effect and plasma defocusing effect in the process of filamentation and promote the stable filament formation of femtosecond pulses in the crystal. The FTRTAS system optimized by 50 mm tight focusing lens generates ultra-stable and widen supercontinuum white light (WL) detection spectrum, with the detection sensitivity increased from 0.75 mOD to 0.3 mOD, which present a great performance in detecting weak signals and tracking carrier evolution of perovskite and carotenoid after photoexcitation. These results indicated that the optimization of the femtosecond laser filamentation system can effectively improve the signal-to-noise ratio, and provide a valuable strategy for optimizing the FTRTAS system.

Keywords: Transient absorption spectroscopyFemtosecond laser filamentationHighly sensitive detectionFocusing elements