Simultaneous generation of ultrabroadband noise-like pulses and intracavity third harmonic at 2 µm.

We demonstrated that ultrabroadband noise-like pulses (NLPs) spanning from below 1600 nm to beyond 2300 nm can be generated in Tm-doped fiber lasers enabled by an optical microfiber. Meanwhile, pronounced red light around 660 nm was also observed, which was attributed to the intracavity third harmonic generation (THG) of ultrashort pulses by harnessing the intermodal phase matching in the optical microfiber. As far as we know, it is the first time to simultaneously observe the ultrabroadband NLPs and the intracavity THG in ultrafast fiber lasers, and it is anticipated that these ultrabroadband NLPs can be adopted as a compact broadband source for optical spectroscopy around 2 µm and a wonderful potential seed for supercontinuum generation in the mid-infrared. Moreover, the THG of the intracavity high peak power NLPs in ultrafast fiber lasers provides a new kind of fiber-format visible light source.