Low Noise, Self-Phase-Modulation-Enabled Femtosecond Fiber Sources Tunable In 740-1236 Nm For Wide Two-Photon Fluorescence Microscopy Applications

We have demonstrated widely tunable Yb:fiber-based laser sources, aiming to replace Ti:sapphire lasers for the nJ-level ultrafast applications, especially for the uses of nonlinear light microscopy. We investigated the influence of different input parameters to obtain an expansive spectral broadening, enabled by self-phase modulation and further reshaped by self-steepening, in the normal dispersion regime before the fiber damage. We also discussed the compressibility and intensity fluctuations of the demonstrated pulses, to reach the transform-limited duration with a very low intensity noise. Most importantly, we have demonstrated clear two-photon fluorescence images from UV-absorbing fluorophores to deep red dye stains.(c) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement