Determination of absolute two-photon excitation cross sections by in situ second-order autocorrelation

Chris Xu, Jeffrey Guild, Watt W. Webb, Winfried Denk

Research output: Contribution to journalArticle

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It is shown that one can obtain absolute two-photon fluorescence excitation (TPE) cross sections without prior knowledge of the temporal profile of the excitation pulse. It is sufficient to record the fluorescence generated by two spatially superimposed but temporally shifted halves of the excitation beam as a function of their relative delay. Measurements employed a Michelson interferometer with a mode-locked Ti:sapphire laser as the excitation source. The TPE cross section for fluorescein [(46 ± 10) × 10-58 m4 syphoton] obtained at 782 nm with this technique agrees with single-mode cw excitation data. We find no indication of a deviation from the power-squared dependence of TPE.

Original languageEnglish (US)
Pages (from-to)2372-2374
Number of pages3
JournalOptics Letters
Issue number23
Publication statusPublished - Dec 1 1995


ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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