Multi-photon microscopy is a widely deployed tool for rapid, in-vivo, volumetric imaging. For three-photon excitation fluorescence microscopy, the necessarily longer wavelength ultrafast pump pulse increases the image penetration depth. Of particular utility are ultrafast sources in the so-called biological imaging windows at 1300 nm and 1680 nm, where the combination of Mie scattering and water absorption create optimal windows of excitation wavelength for maximal image penetration [Horton2013]. As biological tissue is easily damaged with excessive micro-illumination average power, shorter pulse durations (<200 fs) at a set average power increases the output fluorescent signal light.
