Theoretical Investigation of the Dependence of Attenuation of Pulsed Laser Radiation by Fullerene-Containing Solutions on the Pulse Duration

摘要

The dependence of attenuation of laser radiation by fullerene-containing solutions on the laser pulse duration is theoretically studied. The investigation is carried out for a wide range of variations in the pulse durations: from 250 * 10~(-15) to 10~(-8) s. The contribution of two mechanisms (reverse saturable absorption and induced scattering associated with thermal nonlinearity) to the attenuation of radiation is studied. It is shown that reverse saturable absorption makes a considerable contribution to the attenuation in the whole range of durations under consideration, whereas induced scattering exists only in the range of durations that are longer than some nanoseconds. It is shown that the law of similarity with respect to the product of the intensity and the pulse duration for attenuation of laser radiation is approximately fulfilled in the whole range of durations, i.e., the attenuation depends on the energy density. Additionally, the elementary theory of reverse saturable absorption is developed and the limiting values of the absorption coefficient and the maximum attenuation are obtained.