  We demonstrate a significant resolution enhancement beyond the conventional
limit in multiphoton microscopy (MPM) using saturated excitation of
fluorescence. Our technique achieves super-resolved imaging by temporally
modulating the excitation laser-intensity and demodulating the higher harmonics
from the saturated fluorescence signal. The improvement of the lateral and
axial resolutions is measured on a sample of fluorescent microspheres. While
the third harmonic already provides an enhanced resolution, we show that a
further improvement can be obtained with an appropriate linear combination of
the demodulated harmonics. Finally, we present in vitro imaging of fluorescent
microspheres incorporated in HeLa cells to show that this technique performs
well in biological samples.
