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

Abstract

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.