Nine structurally related porphyrins are studied and it is shown how the ma
terial parameters that control the optical limiting depend on the molecular
structure. Optical limiting measurements at 532 nm on the metal-free, zinc
and lead analogues of tetraphenyl porphyrin (TPP), tetra(trimethylsilyethy
nyl) porphyrin (TTMSAP) and tetra(4-n-butylphenylethynyl) porphyrin (TNBBAP
) reveal a strong dependence on the metal atom and peripheral substitution.
A double pump/cw probe technique is used to measure the material parameter
s that control the optical limiting and the results give a strong insight i
nto how the molecular structure influences the individual parameters. These
measurements revealed that one of the materials TTMSAP(Pb) has sigma (ex)/
sigma (gr) ratio of similar to 45 at 532 nm, which is one of the largest va
lues ever reported. Finally, broadband measurements with a picosecond white
-light source show that the position and strength of the excited state abso
rption features also depend strongly on the porphyrin design.