Nonlinear absorption behaviors of filled and unfilled d shell metal complexes of 5, 10, 15, 20-tetrakis(4-hydroxyphenyl)porphyrin

We study nonlinear absorption behaviors of 5, 10, 15, 20-tetrakis(4-hydroxyphenyl)porphyrins with the central metal ions: Zn2+, Ni2+, Co2+, and Fe3+ by open aperture Z-scan technique with 65 ps or 4 ns pulse duration. For 65 ps pulse duration the filled d shell compounds exhibit nonlinear absorption while the unfilled d shell compounds exhibit saturable absorption. For 4 ns pulse duration Ni, Co and Fe compounds exhibit nonlinear absorption at high fluence while Ni compound exhibits saturable absorption at low fluence. The observed nonlinear absorption behaviors depending on the central metal ion and pulse duration are discussed using excited-state lifetimes found from pump–probe spectroscopy.