Published online by Cambridge University Press: 03 September 2012
The fullerene materials are well known for their non-linear behaviour arising from excited state absorption processes. In solution, the processes can set in at low irradiance levels, although evidence is building that the magnitude of the effects is dependent on the solvent used in the experiments and the role of charge transfer processes. In evaporated films of C60, the solvent is absent and reduced non-linearities are seen as irradiances approach the laser damage threshold of the films. When the chromophor is incorporated into polymer films, non-linear processes are found at the same levels as the solution case provided that some residual solvent remains in the composite. Excited state absorption spectra suggest that some ionisation of the C60 may be occuring.