Comparison of the penetration depth in mouse brain through 3PF imaging using AIE nanoparticle labeling and THG imaging within the 1700 nm window.

3-Photon microscopy (3PM) excited at the 1700 nm window features a smaller tissue attenuation and hence a larger penetration depth in brain imaging compared with other excitation wavelengths . While the comparison of the penetration depth quantified by effective attenuation length with other excitation wavelengths have been extensively investigated, comparison within the 1700 nm window has never been demonstrated. This is mainly due to the lack of a proper excitation laser source and characterization of the emission properties of fluorescent labels within this window. Herein, we demonstrate detailed measurements and comparison of through the 3-photon imaging of the mouse brain , at different excitation wavelengths (1600 nm, 1700 nm, and 1800 nm). 3PF imaging and spectrum measurements were performed using AIE nanoparticle labeling. Our results show that derived from both 3PF imaging and THG imaging is the largest at 1700 nm, indicating that it enables the deepest penetration in brain imaging .