Two-photon absorbing chromophores were designed and investigated for optical power limitation based on multiphoton absorption processes. These molecules combine very large two-photon absorption cross-sections (with typical sigma(2p) maximum values of 3 x 10(-20) cm(4) GW(-1) at 735 nm) and large excited-state cross-sections (with typical maximum sigma(e) values of 5 x 10(-16) cm(2)) in the red-NIR region, as shown by two-photon-excited fluorescence and pump-probe Kerr ellipsometry experiments. Numerical simulations demonstrate that these chromophores show a strongly nonlinear absorption behavior suitable for optical limiting of ns pulses (with threshold values down to 1.5 x 10(-2) J cm(-2) for 0.55 ns pulses). (C) 2003 Elsevier B.V. All rights reserved.