We optimized the spectral coverage of self-phase-modulation-enabled femtosecond fiber sources by careful investigations into the influence of input pulse width, fiber length, and fiber damage, and we have demonstrated a widely tunable source ranging from 740-1250 nm for two-photon microscopy applications. In addition, tens of milliwatt tunable near-UV/visible spectrum is easily obtained by a frequency-doubled conversion, and the gap between the fundamental and frequency-doubled spectra can be filled with the nonlinear wave breaking around 650 nm. A multi-modality microscopy incorporating two-photon microscopy and confocal fluorescence microscopy was also demonstrated to prove the versatility of our development for biomedical imaging.
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