The intensity of two-photon-excited fluorescence measured relative to the intensity of hyper-Rayleigh scattering in the same apparatus was used to determine the two-photon-excited fluorescence cross sections of the xanthene dyes Rhodamine B, Rhodamine 6G, and Fluorescein. The measured cross sections at λ<sub>0</sub>= 1064 nm are σ<sub>2PF</sub><sup>(2)</sup>=1.5±0.3×10<sup>−50</sup> cm<sup>4</sup> s, 2.0±0.4×10<sup>−50</sup> cm<sup>4</sup> s, and 1.4±0.3×10<sup>−52</sup> cm<sup>4</sup> s, for the three dyes, respectively. The two-photon-excited fluorescence cross section of Rhodamine B was also calibrated with one-photon-excited fluorescence in this apparatus. The result, σ<sub>2PF</sub><sup>(2)</sup>=2.3±0.7×10<sup>−50</sup> cm<sup>4</sup> s, is in reasonable agreement with the result calibrated by hyper-Rayleigh scattering. The results for Rhodamine B are 1.5–6 times smaller than previous results calibrated by one-photon-excited fluorescence.
© 1999 Optical Society of America
(190.4180) Nonlinear optics : Multiphoton processes
(190.4710) Nonlinear optics : Optical nonlinearities in organic materials
(300.2530) Spectroscopy : Fluorescence, laser-induced
(300.6410) Spectroscopy : Spectroscopy, multiphoton
Philip Kaatz and David P. Shelton, "Two-photon fluorescence cross-section measurements calibrated with hyper-Rayleigh scattering," J. Opt. Soc. Am. B 16, 998-1006 (1999)