3 November 2003 Cooperative enhancement of two- and three-photon absorption in dendrimers and their underlying coherent domain structure
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At present a special attention is concentrated on increasing of the efficiency of multi-photon absorption of organic systems because of new emerging applications based on this effect. In our experiments we use strong two-photon absorbing chromophore, 4,4’-bis(diphenylamino)stilbene (BDPAS), to design new dendrimer molecules, in such a way that the branching center allows for pi-electronic conjugation between branches. Here we present, for the first time, unambiguous spectroscopic evidence of strong cooperative enhancement of two-photon and three-photon absorption in a series of these dendritic macromolecules. Maximum two-photon cross section increases in proportion to N2, where N = 2, 4, 6 is the number of constituent identical chromophore units in the parent BDPAS and lowest, G-0 dendrimer generation. Almost the same scaling law is observed for three-photon absorption. For higher generations, G-1 and G-2, comprising N = 14 and 30 chromophores, respectively, the cooperativity in multiphoton response starts to saturate. We show that three-photon absorption provides important complementary information, which we use for evaluation of the size of domains where chromophores are coherently coupled.
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Mikhail Drobizhev, Mikhail Drobizhev, Aliaksandr Karotki, Aliaksandr Karotki, Yuliya Dzenis, Yuliya Dzenis, Mikalai Kruk, Mikalai Kruk, Aleksander Rebane, Aleksander Rebane, Zhiyong Suo, Zhiyong Suo, Charles W. Spangler, Charles W. Spangler, "Cooperative enhancement of two- and three-photon absorption in dendrimers and their underlying coherent domain structure", Proc. SPIE 5211, Nonlinear Optical Transmission and Multiphoton Processes in Organics, (3 November 2003); doi: 10.1117/12.505761; https://doi.org/10.1117/12.505761

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