On-off resonance femtosecond non-linear absorption of chalcogenide glassy films

Non-linear absorption of chalcogenide thin films has been investigated with femtosecond pump-probe experiments. Different peculiarities of femtosecond pulse absorption have been found in the case of on- and off-resonance pumping and probing, due to either intraband or interband transitions. The physical mechanisms which can explain such different behaviours are discussed.