title: Visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals.
abstract: Further development of multiphoton microscopic imaging is confronted with a number of limitations, including high-cost, high complexity and relatively low spatial resolution due to the long excitation wavelength. To overcome these problems, for the first time, we propose visible-to-visible four-photon ultrahigh resolution microscopic imaging by using a common cost-effective 730-nm laser diode to excite the prepared Nd(3+)-sensitized upconversion nanoparticles (Nd(3+)-UCNPs). An ordinary multiphoton scanning microscope system was built using a visible CW diode laser and the lateral imaging resolution as high as 161-nm was achieved via the four-photon upconversion process. The demonstrated large saturation excitation power for Nd(3+)-UCNPs would be more practical and facilitate the four-photon imaging in the application. A sample with fine structure was imaged to demonstrate the advantages of visible-to-visible four-photon ultrahigh resolution microscopic imaging with 730-nm diode laser excited nanocrystals. Combining the uniqueness of UCNPs, the proposed visible-to-visible four-photon imaging would be highly promising and attractive in the field of multiphoton imaging.
authors.forename: Baoju
authors.initials: B
authors.lastname: Wang
authors.forename: Qiuqiang
authors.initials: Q
authors.lastname: Zhan
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Ruitao
authors.initials: R
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Sailing
authors.initials: S
authors.lastname: He