Si Chen

Abstract Black phosphorus (BP), a burgeoning elemental 2D semiconductor, has aroused increasing scientific and technological interest, especially as a channel material in field‐effect transistors (FETs). However, the intrinsic instability of BP causes practical concern and the transistor performance must also be improved. Here, the use of metal‐ion modification to enhance both the stability and transistor performance of BP sheets is described. Ag + spontaneously adsorbed on the BP surface via cation–π interactions passivates the lone‐pair electrons of P thereby rendering BP more stable in air. Consequently, the Ag + ‐modified BP FET shows greatly enhanced hole mobility from 796 to 1666 cm 2 V −1 s −1 and ON/OFF ratio from 5.9 × 10 4 to 2.6 × 10 6 . The mechanisms pertaining to the enhanced stability and transistor performance are discussed and the strategy can be extended to other metal ions such as Fe 3+ , Mg 2+ , and Hg 2+ . Such stable and high‐performance BP transistors are crucial to electronic and optoelectronic devices. The stability and semiconducting properties of BP sheets can be enhanced tremendously by this novel strategy.

Abstract 2D titanium disulfide (TiS 2 ) is recently found to have strong light absorption properties from visible to infrared (IR) region. This feature is highly attractive for applications in nonlinear photonics; however, the mechanism of broadband light–matter interaction is yet to be determined and nonlinear photonic devices are not developed. Here, for the first time, the experimental evidence supporting the mechanism of the broadband nonlinear photoresponse in ultrathin TiS 2 nanosheets ranging from 400 nm to 1390 nm is reported through laser Z ‐scan measurements. High‐performance nonlinear photonic devices operating in the telecommunication band are also demonstrated. A novel saturable absorber (SA) device is successfully fabricated based on a 2D TiS 2 ‐decorated fiber, which exhibits outstanding ultrashort pulse generation performance with pulse duration of ≈1.04 ps centered at 1569.5 nm. Furthermore, as a stable all‐optical thresholding component, the device can effectively attenuate noise and boost the signal‐to‐noise ratio of the pulse from 1.90 to 10.68 dB. The findings indicate that TiS 2 ‐based SA devices can be developed into excellent highly nonlinear photonic devices, which may advance the development of TiS 2 ‐based optical communication technologies in the future.

We report on the optical saturable absorption of few-layer black phosphorus nanoflakes and demonstrate its application for the generation of vector solitons in an erbium-doped fiber laser. By incorporating the black phosphorus nanoflakes-based saturable absorber (SA) into an all-fiber erbium-doped fiber laser cavity, we are able to obtain passive mode-locking operation with soliton pulses down to ~670 fs. The properties and dynamics of the as-generated vector solitons are experimentally investigated. Our results show that BP nanoflakes could be developed as an effective SA for ultrashort pulse fiber lasers, particularly for the generation of vector soliton pulses in fiber lasers.

Two-dimensional (2D) black phosphorus (BP) shows thickness dependent direct energy band-gaps in association with strong light-matter interaction and broadband optical response, rendering it with promising optoelectronic advantages particularly at the telecommunication band. However, intrinsic BP suffers from irreversible oxidization, restricting its competences toward real device applications. As one potential of 2D materials, all-optical signal processing sensitively depends on the strength of light–matter interaction. BP can be utilized as a novel optical medium. Herein, few-layer BP is synthesized with metal-ion-modification against oxidation and degradation, and then the feasibility of BP-coated microfiber as an optical Kerr switcher and a four-wave-mixing-based wavelength converter is demonstrated. The wavelength-tuning, long-term stability, wide-band RF frequency, and time-repeating measurements confirm that this optical device can operate as a broadband all-optical processor. It is further anticipated that metal-ion-modified BP might provide a new effective option for photonic applications toward high performances and enhanced stability.

A facile and scalable step-wise approach has been developed to fabricate graphene-based TiO2/SnO2 hybrid nanosheets (TiO2@SnO2@GN). With uniform staggered distribution of rutile SnO2 and TiO2 nanocrystals in a 2D mesoporous manner, TiO2@SnO2@GN with low content of graphene (∼5 wt%) manifests superior reversible capacity and excellent rate capability as an anode material in lithium-ion batteries.