title: Measurements of multiphoton action cross sections for multiphoton microscopy.
abstract: We report quantitative measurements of two-, three-, and four-photon excitation action cross sections of several commonly used fluorophores and fluorescent proteins at three different excitation wavelengths of 800 nm, 1300 nm, and 1680 nm. The measured cross section values are consistent with simple quantum mechanic estimations. These values indicate that the optimum repetition rate for deep tissue 3-photon microscopy is approximately 1 to 2 MHz. We further demonstrate that it is feasible to perform 4-photon fluorescence microscopy of GFP labeled microglia in mouse brain in vivo at 1700 nm. 4-photon excitation increases the accessibility of fluorophores at the long wavelength spectral window of 1700 nm.
authors.affiliation: Department of Photonics, National Cheng Kung University, Tainan 701, Taiwan ; School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Li-Chung
authors.initials: LC
authors.lastname: Cheng
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Horton
authors.affiliation: Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 China.
authors.forename: Ke
authors.initials: K
authors.lastname: Wang
authors.affiliation: Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan ; Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Shean-Jen
authors.initials: SJ
authors.lastname: Chen
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Xu
keywords: (190.0190) Nonlinear optics; (190.4180) Multiphoton processes