Low-threshold supercontinuum generation and optimization of PCF-intracavity-excited Q-switched fiber lasers

We experimentally demonstrate a low-pump-threshold all-fiber supercontinuum (SC) source based on PCF-intracavity-excited Q-switched laser. By inserting a silica PCF into 1.06μm actively Q-switched double-clad Yb-doped fiber lasers, a flat SC in the wavelength range of 500-1950 nm can be efficiently initiated with a low SC pump-threshold and the SC output power of >420mW. By optimizing the parameters of active Q-switching, we find that the Q-switched repetition rate and modulation duty significantly influence on the SC pump threshold. With the repetition rate of 100 Hz and the modulation duty of <5%, the SC pump threshold is as low as 0.3 W, which is, to the best of our knowledge, the lowest one reported previously. Moreover, by observing the temporal and spectral evolution, we experimentally reveal and understand the physical mechanisms of the SC generation in such long-pulse intracavity-pumping PCF scheme.