Cu2S nanosheets for ultrashort pulse generation in the near-infrared region

Abstract

2D metal chalcogenide materials have received enormous attention due to their extraordinary bio-chemical, electronic, magnetic, thermal and optical properties. Compared with the typical two-dimensional transition metal dichalcogenides (TMDs) and topological insulators, cuprous sulfide (Cu₂S) has very different two-dimensional lattice structures, along with excellent electro-catalysis and high conductivity. However, the nonlinear optical properties of Cu₂S have never been studied until now. Here, the nonlinear photonics characteristics of Cu₂S and its application in ultrafast lasers have been systematically studied for the first time. Through optical deposition of Cu₂S nanosheets on a tapered fiber, the nonlinear optical properties of Cu₂S nanosheets are measured through the interaction with the evanescent field. The results indicate that superior nonlinear saturable absorption properties with a modulation depth of 0.51% are achieved. An erbium-doped fiber (EDF) laser is constructed to verify the performance of the Cu₂S saturable absorber (SA). The results show that an output pulse with 8.06 MHz repetition rate, 1.04 ps pulse duration, 1530.4 nm central wavelength and 3.1 nm spectral width without an obvious Kelly sideband is obtained. Considering the diversity of the metal chalcogenide family, various engineering applications may be developed from the nonlinear saturable absorption characteristics of Cu₂S, including optical fiber communication/sensing, precision optical metrology, material processing and nonlinear optics.