Three‐photon microscopy excited at the 1700‐nm window enables deep‐tissue penetration. However, the refractive indices of commonly used immersion oils, and the resultant pulse broadening are not known, preventing imaging optimization. Here, we demonstrate detailed characterization of the refractive index, pulse broadening and distortion for excitation pulses at this window for commonly used immersion oils. On the physical side, we uncover that absorption, rather than material dispersion, is the main cause of pulse broadening and distortion. On the application side, comparative three‐photon imaging results indicate that 1600‐nm excitation yields 5 times higher three‐photon signal than 1690‐nm excitation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.