Emerging High-Performance SnS/CdS Nanoflower Heterojunction for Ultrafast Photonics.

Metal sulfide nanomaterials show many unique photoelectric properties when they are constructed as heterojunction materials, which have made them attractive in recent years. Among various applications of these heterojunction materials, nonlinear optical properties and related applications are promising research fields. Herein, a novel high performance SnS/CdS nanoflower heterostructure is successfully prepared by a water bath method. Scanning electron microscopy (SEM) images suggest the formation of a nanoheterojunction between SnS and CdS. In addition, a large modulation depth (13.6%) and a low saturation intensity (230.6 MW/cm2) of the SnS/CdS heterostructure are demonstrated, which indicates the outstanding potential of the SnS/CdS heterostructure in photonics among the other emerging novel nonlinear optical (NLO) materials. Meanwhile, the surface morphology, structures, and optical characteristics of the as-prepared SnS/CdS nanoflower sample are systemically analyzed. Furthermore, an ultrashort pulse laser with a fundamental repetition rate of 34.3 MHz, a pulse width of 558 fs, and a spectral width of 8.6 nm is realized at a central wavelength of 1560.8 nm. More importantly, we have successfully realized a soliton molecule with controllable pulse-pulse separation from 2.8 to 10.2 ps by controlling the phase difference of the cavity. This work reveals the excellent nonlinear optical properties of the SnS/CdS heterostructure and lays a foundation for its development in advanced optical modulators, saturable absorbers, and optical switching devices.