ABSTRACT
A simple approach to multi-color two-photon microscopy of the red, green, and blue fluorescent indicators was reported based on an ultra-compact 1.03-µm femtosecond laser and a nonlinear fiber. Inside the nonlinear fiber, the 1.03-µm laser pulses were simultaneously blue-shifted to 0.6~0.8 µm and red-shifted to 1.2~1.4 µm region by the Cherenkov radiation and fiber Raman gain effects. The wavelength-shifted 0.6~0.8 µm and 1.2~1.4 µm radiations were co-propagated with the residual non-converted 1.03-µm pulses inside the same nonlinear fiber to form a fiber-output three-color femtosecond source. The application of the multi-wavelength sources on multi-color two-photon fluorescence microscopy were also demonstrated. Overall, due to simple system configuration, convenient wavelength conversion, easy wavelength tunability within the entire 0.7~1.35 µm bio-penetration window and less requirement for high power and bulky light sources, the simple approach to multi-color two-photon microscopy could be widely applicable as an easily implemented and excellent research tool for future biomedical and possibly even clinical applications.
