Enhanced two-photon absorption with dimers of π-conjugated molecules

International audienceThe two-photon absorption (TPA) of three organic monomers and dimers with different conjugated systems (biphenyl, fluorene and stilbene) is investigated. Quantum chemistry calculations show an order of magnitude enhancement of the dimer TPA in comparison to the monomer TPA, and an increase of TPA with the strength of the conjugated system. The measured TPA spectra of dimers are in good agreement with calculations. At resonance, the TPA cross-sections of biphenyl, fluorene and stilbene dimers are 1.5, 6 and 13×10−49 cm4 s/photon-molecule, respectively