No abstract

As a member of the 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, extraordinary metal‐like ductility, high plastic deformation strain, unique layered structure, and very low solubility has offered a platform for achieving tremendous success in various fields. Great achievements have been made in exploring the linear optical, mechanical, and photoelectric properties of 2D Ag2S nanosheets. However, the nonlinear optical properties of 2D Ag2S nanosheets and their applications in ultrafast photonics have not been studied. The saturable absorption property of 2D Ag2S nanosheets is experimentally illustrated at the telecommunication band with a large optical modulation depth of 15.5% and a low saturable intensity of 250.4 MW cm−2. Moreover, the 229th harmonic soliton molecule with repetition rate of 1.1 GHz based on 2D Ag2S saturable absorber is realized at the telecommunication band for the first time to the authors' knowledge. Thankfully, 2D Ag2S nanosheets display excellent nonlinear optical properties suggesting that this may open a new door for advanced photonic devices based on 2D Ag2S nanosheets.

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/cm 2 ) 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.

The effects of the hyperbranched polyester with hydroxyl end groups (HBPE-OH) on the curing behavior and toughening performance of a commercial epoxy resin (diglycidyl ether of bisphenol A, DGEBA) were presented. The addition of HBPE-OH into DGEBA strongly increased its curing rate and conversion of epoxide group due to the catalytic effect of hydroxyl groups in HBPE-OH and the low viscosity of the blend at curing temperature. The improvements on impact strength and critical stress intensity factor (or fracture toughness, K 1c ) were observed with adding HBPE-OH. The impact strength was 8.04 kJ m À1 when HBPE-OH reached 15 wt% and the K 1c value was approximately two times the value of pure epoxy resin when HBPE-OH content was 20 wt%. The morphology of the blends was also investigated, which indicated that HBPE-OH particles, as a second phase in the epoxy matrix, combined with each other as the concentration of HBPE-OH increased. HBPE-OH has on average eight -OH end groups per molecule. DGEBA was supplied by Wuxi Resin Factory, China, with an epoxide value of 0.51-0.53 mmol g À1 . mPDA, as a curing agent, was supplied by Shanghai First Reagent Co., China. These materials were used as received without further purification. The chemical structures of the epoxy resin, hardener, and HBPE-OH are shown in Fig. 1.