Two-photon absorption standards in the 550-1600 nm excitation range: establishing a correction curve for accurate cross section calibration

We present a modified fluorescence excitation technique for the measurement of absolute two-photon absorption cross section and spectra. We take into account the variations of pulse duration and beam intensity profile as functions of excitation wavelength, which allows determining the 2PA cross section values with the absolute fidelity ±10% in a broad range of wavelengths. On the example of Rhodamine 610 in methanol we discuss various factors that can influence the accuracy of 2PA spectra. Ways how to further increase the accuracy of 2PA measurement are discussed.