Design and synthesis of heterocyclic multi-branched dyes for two-photon absorption

We report the first example of a heterocycle-based multi-branched two-photon absorption (TPA) dye. We show that the new chromophore presents a very large TPA cross-section in the femtoseconds (fs) regime. Comparison of the TPA cross-sections between the branched system and the corresponding monomeric unit shows a strong cooperative enhancement. A value of 22.6:1, corresponding to a 750% enhancement, was observed. (C) 2003 Elsevier Science B.V. All rights reserved.