Two types saturable absorbers based few-layer CoTe2 nanosheets for generation of bright-dark soliton pairs in erbium-doped fiber lasers

We have achieved stable bright-dark soliton pairs in an erbium-doped fiber laser (EDFL) with two types CoTe2 based saturable absorbers. In this experiment, we used two types of saturable absorbers (SAs), sandwiched structure and tapered fiber, fabricated based on CoTe2. By carefully tuning the polarization controller and the pump power, we achieved bright-dark soliton pairs by the SA with the sandwiched structure at a pump power of 400 mW in a fiber laser. At a pump power of 655 mW, bright-dark soliton pairs obtained in the fiber laser using SA with tapered fiber. The spectra of the bright-dark soliton pairs both possess symmetrically distributed Kelly sidebands. To the best of our knowledge, this is the first time that bright-dark soliton pairs have been realized in two CoTe2 SAs based fiber laser. This work not only demonstrate the excellent optical properties of CoTe2, but also have important impacts for the study of dark solitons.