Ultrashort pulse duration and broadband dual-comb laser system based on a free-running passively mode-locked Er-fiber oscillator

We have demonstrated pulse duration compression and wavelength extension to a dual-comb free-running passively mode-locked Er-fiber oscillator. At first, the pulse duration of the dual-comb ultrashort pulses from the oscillator is nonlinearly compressed to similar to 50 fs by fiber amplifiers. Then, a dual-comb supercontinuum laser source with broadband wavelength band from 1.0 to more than 1.75 mu m is achieved when the compressed pulses are used to pump highly nonlinear fibers. At last, utilizing the dual-comb supercontinuum source as the seed for spectral-selected Yb-fiber amplifiers, sub-100 fs ultrashort pulses are obtained at 1.0 mu m. This free-running dual-comb fiber laser system can provide ultrashort pulses with sub-100 fs pulse duration at 1.0 mu m, 1.5 mu m and broadband supercontinuum covering 1.0 to more than 1.75 mu m, so it can be potentially deployed in dual-comb applications such as absolute distance measurement, coherent anti-stokes Raman spectroscopy, and mid-infrared differential frequency generation.