Nanosecond and picosecond nonlinear absorption studies of a highly nonlinear organic liquid for optical limiting application

Nonlinear transmission and optical limiting of picosecond and nanosecond laser pulses in an organic fiber core liquid are investigated. The measured effective absorption coefficients and other limiting characteristics are analyzed using a model that accounts for linear, two-photon, intermediate, and excited-state absorptions. In the picosecond regime, two-photon absorption process is the dominant mechanism. On the other hand, in the nanosecond and longer time scale, other processes such as excited state absorption and nonlinear scattering contribute significantly, giving rise to an effective nonlinear absorption coefficient that can be two orders of magnitude larger than the picosecond counterpart.