Active tuning of nonlinear absorption in a supramolecular zinc diphenylporphyrin-pyridine system

We report on an active tuning of nonlinear absorption from reverse saturable absorption to saturable absorption in supramolecular zinc diphenylporphyrins by the combination of molecular and supramolecular levels at 532, 542 and 552 nm. Firstly, the modifications of molecular structures with bromination result in a discrete but regular change in magnitude and sign of nonlinear absorption (NLA). Furthermore, a fine tuning of NLA was obtained by the intermolecular weak interaction of pyridine and zinc porphyrins. Using an association model, we theoretically simulate the change of NLA. Compared with modifying molecular structures of conventional organic materials, the weak intermolecular interaction of supramolecular porphyrins has another advantage that it can be realized more easily and flexibly to change NLA. (c) 2006 Optical Society of America