Optical nonlinearities of alcoholic liquids under high-repetition-rate femtosecond lasers by single beam time-resolved eclipsed Z-scan

The experiments and applications of nonlinear optical liquids are often complicated by the presence and competition of the fast self-focusing and slow self-defocusing effects. As a result, the time-resolved measurements of liquids nonlinearities are very crucial. In this work, the temporal evolution of optical nonlinearities due to the accumulation of thermal effect for alcoholic liquids-frequently adpoted as the solvent of many organic nonlinear molecules and used in many nonlinear optical experiments-under high-repetition-rate femtosecond lasers is demonstrated using single beam time-resolved eclipsed Z-scan, that is, the combination of single beam time-resolved Z-scan and eclipsed Z-scan methods. The pure self-focusing nonlinearities arising from molecular reorientation of alcoholic liquids can be precisely extracted by a simple data processing. It can be concluded that the characteristic time of the accumulation of thermal nonlinear optical effects is 479.28 and 601.62 μs, and the fast self-focusing effects will be completely masked by the thermal nonlinear optical effects after t = 17.35 and 22.25 μs of laser irradiation for methanol and ethanol, respectively. The “combined” Z-scan technique can also have an extensive application for other advanced materials.