A new effect of nonlinear absorption and description using semiclassical theory

Summary form only given. In this paper we reported a new effect that the nonlinear absorption is changed from reverse saturable absorption (RSA) into saturable absorption (SA) at higher fluences of ps laser. SA in this case is due to the singlet second exited-state absorption which is stronger than that of the ground-state or/and the singlet first exited-state.<
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