  We present an entirely fiber based laser source for non-linear imaging with a
novel approach for multi-color excitation. The high power output of an actively
modulated and amplified picosecond fiber laser at 1064 nm is shifted to longer
wavelengths by a combination of four-wave mixing and stimulated Raman
scattering. By combining different fiber types and lengths, we control the
non-linear wavelength conversion in the delivery fiber itself and can switch
between 1064 nm, 1122 nm, and 1186 nm on-the-fly by tuning the pump power of
the fiber amplifier and modulate the seed diodes. This is a promising way to
enhance the applicability of short pulsed laser diodes for bio-molecular
non-linear imaging by reducing the spectral limitations of such sources. In
comparison to our previous work [1, 2], we show for the first time two-photon
imaging with the shifted wavelengths and we demonstrate pulse-to-pulse
switching between the different wavelengths without changing the configuration.
