Fig. 5.

(a) 200 nm fluorescence beads (polystyrene, surface modification by carboxylate) image from TPEF signals, excited by a FOPG pulsed laser for multimodal nonlinear imaging (pump beam at 795 nm and Stokes beam at 1030 nm, 5 MHz repetition rate, 22 mW, and 110 mW average power at the sample, respectively for pump and Stokes). Filter: BP514/3. (b), (d), and (e) Lateral PSF of points framed by red, blue, green squares in panel (a), with pixel size of $0.13\mu \mathrm{m}$ in width, $4\mu \mathrm{s}$ in dwell time, and frame averaged by eight times. (c) Axial PSF of a point at the central field, i.e., point framed by the red square in panel (a). Stack step is $0.5\mu \mathrm{m}$ in $z$ direction. Images were acquired by the ScanImage (Vidrio Technologies).³³