Heavy atom effect on nonlinear absorption and optical limiting characteristics of 5,10,15,20-(tetratolyl) porphyrinato phosphorus (V) dichloride

Optical limiting performance and third-order nonlinearity chi((3)) are investigated in 5,10,15,20-(tetratolyl) porphyrinato phosphorus (V) dichloride ([(TTP)(PCl2)-Cl-V](+)). Heavy atom effect exerted by the two axial chlorides is found to result in low fluorescence yield (empty set(n)), shorter lifetimes of S-1, T-1 and faster intersystem crossing (ISC), leading to larger excited state absorption (ESA) from T-1 --> T-n This phenomenon is found to lower the limiting threshold by 30 times and increase the second hyperpolarizability by one and three orders in ps and ns time regimes, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.