Nonlinear imaging using a 35 fs 3.5 nJ all-PM fiber laser frequency doubled at 800 nm

We demonstrate the use of an all-PM fiber laser, delivering 35 fs pulses at 800 nm and a 40-MHz repetition rate, for two-photon excited fluorescence (2PEF) and Second Harmonic Generation (SHG) nonlinear microscopy. The laser has been combined to a compact group delay dispersion pre-compensation set-up to ensure the shortest pulse and so the highest peak power on the sample, minimizing the risk to damage it. We carried out measurements on vegetal samples like vine shoot or cleaning paper as well as on the forefinger of a volunteer, for current biocompatible powers under 10 mW. To the best of our knowledge, the use of an all-PM fiber laser delivering 35 fs pulses for microscopy applications has never been reported. Due to its compactness and cost-efficiency, this laser is a very attractive alternative to Ti:Sapphire mode-locked lasers.