Abstract

The nonlinear absorption properties of organic materials in nanosecond (ns), picoseond (ps) and femtosecond (fs) regime were theoretically investigated by rate equations based on multilevel organic molecular system respectively. The results show that the reverse saturable absorption (RSA) phnomenon is mainly due to the absorption contribution of the triplet first excited state in the ns regime, and that of the singlet first excited state in the ps regime, both of which are a third-order nonlinear phenomena. The RSA phnomenon in fs regime is mainly due to the excited state absorption (ESA) induced by two-photon absorption (TPA), which is a fifth-order nonlinear phenomenon.

© 2012 Optical Society of America