Broad bandwidth near-IR two-photon absorption in conjugated porphyrin-core dendrimers

Aleks Rebane; Nikolay Makarov; Mikhail Drobizhev; Charles W. Spangler; Aijun Gong; Fanqing Meng

doi:10.1117/12.734475

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28 September 2007 Broad bandwidth near-IR two-photon absorption in conjugated porphyrin-core dendrimers

Aleks Rebane, Nikolay Makarov, Mikhail Drobizhev, Charles W. Spangler, Aijun Gong, Fanqing Meng

Author Affiliations +

Proceedings Volume 6653, Linear and Nonlinear Optics of Organic Materials VII; 665307 (2007) https://doi.org/10.1117/12.734475
Event: Photonic Devices + Applications, 2007, San Diego, California, United States

Abstract

We study two-photon absorption (2PA) spectra and absolute 2PA cross sections, as well as fluorescence emission- and excitation spectra along with time resolved fluorescence in a series of new dendrimers, where a single porphyrin/phthalocyanine core is decorated with electron-donating/two-photon absorbing groups. We show that if the combined system has strong π-conjugation/multipolar charge transfer between the core and the attached group(s), then the observed 2PA undergoes cooperative enhancement, where the peak 2PA cross section reaches σ₂=600-2000 GM in a broad transition wavelength region 375-500 nm (laser wavelengths 750-1000 nm). In the systems with less conjugation, the 2PA is less enhanced, and in the limit of very weak conjugation maximum σ₂ remains essentially the sum of the cross sections of the constituents. We show that the conjugation strength correlates with the fluorescence emission properties. In particular, in the strongly linked systems the fluorescence originates mostly from the core porphyrin, whereas in the weakly linked systems the attached chromophores emit independently from the porphyrin. In intermediate conjugation strength case we observe non-exponential fluorescence decays and fluorescence rise times, which indicated Forster resonant energy transfer from the side groups to the core.

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Aleks Rebane, Nikolay Makarov, Mikhail Drobizhev, Charles W. Spangler, Aijun Gong, and Fanqing Meng "Broad bandwidth near-IR two-photon absorption in conjugated porphyrin-core dendrimers", Proc. SPIE 6653, Linear and Nonlinear Optics of Organic Materials VII, 665307 (28 September 2007); https://doi.org/10.1117/12.734475

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