The Investigation Of Ultrafast Nonlinear Absorption Dynamics And Broadband Optical Limiting Properties On Pyrene-based Derivative

The invention of laser has greatly promoted the progress of the society, it has been widely used in scientific research, military, medical and other fields. While the laser is also a double-edged sword, which also brings much threat to human and optical equipment. As a result, much attention is attracted to design the optical limiting materials and devices for protecting optical detectors from high optical density damage.Here, the broadband nonlinear optical response of a new symmetric pyrene derivative is investigated by means of multi-wavelengths femtosecond(fs) Z-scan measurement. According experimental results, reverse saturation absorption are observed at all experimental wavelengths. The nonlinear absorption mechanism of the sample is analyzed by combination the time-resolved pump-probe measurement at 515 nm with the linear absorption spectrum. At this wavelength, the nonlinear absorption mechanism of the sample is originated from two-photon absorption and two-photon absorption induced excited state absorption induced. Based on five-energy-level model and the rate equation, the optical physical parameters such as energy level lifetimes and the excited state absorption cross section at 515 nm are extracted by numerical simulation..The nonlinear absorption characteristics of titled sample under different wavelength excitation is investigated by femtosecond transient absorption spectrum. The experimental results show that the sample experiences excited-state absorption properties in a wide spectral range from 470 nm to 780 nm after pumped at 350 nm. The internal energy relaxation process is determined by global fitting of optical kinetic curves. Based on simplified three-energy-level model at femtosecond condition, two nonlinear absorption parameters(two-photon absorption coefficient and the excited state absorption cross section) of the sample under different wavelengths are extracted from open-aperture Z-scan curves with different energies through numerical simulation. Finally, the broadband optical limiting experiments of titled sample are carried out. The experimental results show that the two-photon absorption coefficient and the excited state absorption cross section are proportional to the optical limiting capacity of the sample. By comparing with the known literature, the sample performs excellent broadband optical limiting behavior, indicating that it can be used as a potential ideal optical limiting material in the ultrafast field.