Effects of conjugation length and resonance enhancement on two-photon absorption in phenylene–vinylene oligomers

Mette Johnsen, M.J. Paterson, J. Arnbjerg, O. Christiansen, Christian Bech Nielsen, Mikkel Jørgensen, P.R. Ogilby

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Two-photon excitation spectra have been recorded over the large spectral range of 540-1000 nm for five phenylene-vinylene oligomers that differ in the length of the conjugated p system. The significant changes observed in the two-photon excitation spectra and absorption cross sections as a function of this systematic change in the chromophore are discussed in light of (1) the corresponding one-photon absorption spectra and (2) high-level density functional response theory calculations performed on analogues of these systems. The results obtained illustrate one way to exploit parameters that influence nonlinear optical properties in large organic molecules. Specifically, data are provided to indicate that when the frequency of the laser used in the two-photon experiment is nearly-resonant with an allowed one-photon transition, significant increases in the two-photon absorption cross section can be realized. This phenomenon of the so-called resonance enhancement allows for greater control in obtaining an optimal response when using existing two-photon chromophores, and provides a much-needed guide for the systematic development and efficient use of two-photon singlet oxygen sensitizers.
    Original languageEnglish
    JournalPhysical Chemistry Chemical Physics
    Volume10
    Issue number8
    Pages (from-to)1177-1191
    ISSN1463-9076
    DOIs
    Publication statusPublished - 2008

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