Abstract
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
σ
2p maximum values of 3
×
10
−20 cm
4 GW
−1 at 735 nm) and large excited-state cross-sections (with typical maximum
σ
e values of 5
×
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
×
10
−2 J cm
−2 for 0.55 ns pulses).