▎ 摘　　要

Van der Waals (vdW) heterostructures offer a promising platform for optimizing and controlling physical properties of a variety of materials and devices, which has attracted extensive attentions in ultrafast photonic applications. Here, a hybrid vdW saturable absorber (SA) based on ZnO sphere heterostructures has been fabricated by transferring the low-temperature hydrothermal method ZnO spheres onto gold mirrors and covering with Au nanoparticles and the graphene layer. In comparison with the ZnO sphere SA, the vdW SA exhibits the stronger emission intensity in the ultraviolet-visible range and the higher optical absorption in the near-infrared range, respectively. Meanwhile, by using the balanced twin-detector technology, a modulation depth of 6.6% has been obtained from vdW SA, which is 2.8 times greater than that of the solo ZnO SA due to the harvest of photons and the transfer of photon-generated carriers in the vdW heterostructure. Based on the hybrid vdW SA, a quite stable Q-switched laser and a mode-locked laser operation with a tunable wavelength range from 1531.4 to 1560.4 nm have been achieved. These results demonstrate a effective strategy for enhancing nonlinear optical properties of SAs and pave a way for de-veloping novel types of SAs for the application of ultrafast lasers.(c) 2022 Elsevier B.V. All rights reserved.