OPTICAL LIMITING PROPERTIES AND DYNAMICS OF INDUCED ABSORPTION IN C-60-DOPED SOLID XEROGEL MATRICES

We present measurements of induced absorption and its dynamics in C-60 -doped solid xerogel matrices. The measurements are performed in a pum p-test geometry using picosecond pulses generated from a frequency dou bled mode locked Nd:YAG laser at 532 nm. We observe an induced absorpt ion leading to optical limiting. We find outstanding optical limiting qualities for single shot excitation but some degradation above a cert ain threshold intensity for repetitive pulses. Below this degradation threshold, the material is stable and its limiting dynamics is studied . A decrease of the initial laser-induced absorption with a time const ant of 150 ps is observed, down to a very long-lived constant level. W e attribute this dynamics of induced absorption to a transition from e xcited singlet to triplet electronic states in the C-60 molecule. (C) 1998 American Institute of Physics. [S0021-9606(98)51420-1].