Figure 2.
A representative lateral, r, and axial, z, ISPF2 from a 100-nm fluorescent bead (a), indicating average lateral and axial FWHMs of 460 and 1760 nm, respectively. The inset shows the two-photon image of a typical bead in the rz-plane. Autocorrelation measurements with a 1 in. singlet lens (b) and with a 20x∕0.95 objective lens (c) indicated duration FWHMs of 185 ± 10 and 270 ± 10 fs, respectively. Double-headed arrows in each plot indicate where the FWHM was measured. Fluorescent signal (Fl) is normalized to 1 at the center of the bead in (a), and at 1.5 ps in (b) and (c).