High-energy polarized soliton synthesis and its application to deep-brain 3-photon microscopy in vivo

Here, we demonstrate a polarized high-energy soliton synthesis technique for deep-brain 3-photon microscopy (3PM) excited at the 1700-nm window. Through coherent combining, we generate linearly polarized high-energy solitons whose energy is twice as high than those of each linearly polarized solitons. Due to the nonlinear origin of signals, both measured 3-photon fluorescence signal and third-harmonic signals are thus boosted by ~8 times in a tissue phantom. Using this technique, we further demonstrate 3PM of sulforhodamine 101 labeled vasculature 1600 μm in the mouse brain in vivo, which cannot be achieved by single-polarized soliton excitation.