Tunable nonlinear optical responses and carrier dynamics of two-dimensional antimonene nanosheets

Optical quantification of the weak van der Waals coupling between multilayer antimonene and bilayer MoS2 using ultrafast coherent vibration spectroscopy

Antimonene, a promising conductor for next-generation 2D-based devices, has its contact resistance significantly influenced by the van der Waals (vdW) interaction within its heterostructure. In this study, we report the quantification of the vdW coupling between multilayer antimonene and bilayer MoS2 by ultrafast coherent vibration spectroscopy. By utilizing a femtosecond laser, we excited coherent acoustic vibrations in the multilayer-antimonene on substrate-supported bilayer MoS2, and the relative displacement at the vdW heterojunction was detected with the aid of bilayer MoS2. The photoexcited strain pulse generated in the multilayer-antimonene was observed as it transported to the bilayer MoS2, explaining the distortion at the beginning of the oscillation. By analyzing the thickness-dependent oscillation frequencies, we determine the effective vdW elastic constant between multilayer-antimonene and MoS2 to be (1.9 ± 0.2) × 1018 N/m3. This non-destructive optical technique offers a significant advance in the evaluation of vdW interactions at 2D metal-semiconductor interfaces.

Unveiling the dimension-dependence of femtosecond nonlinear optical properties of tellurium nanostructures

Low dimensional tellurium is currently of great interest for potential electronic applications due to the experimentally observed Weyl fermions and the excellent carrier mobility, on/off ratios and current-carrying capacity in devices. However, the optical properties of Te nanostructures are not well explored, especially in the field of nonlinear optics. Here, we prepared a series of Te nanostructures by electrochemical exfoliation and liquid phase exfoliation methods, including one-dimensional (1D) Te nanowires (NWs), quasi-1D Te nanorods (NRs), zero-dimensional (0D) Te nanodots (NDs) and two-dimensional (2D) Te nanosheets (NSs). Femtosecond Z-scan measurements reveal unique dimension-dependent nonlinear optical (NLO) properties. 1D Te NWs and quasi-1D Te NRs exhibited higher saturable absorption behavior than 0D Te nanostructures, while the 2D Te NSs are a high performance optical limiting material. Ultrafast transient absorption spectroscopy revealed the dimension-dependent exciton dynamics. The reverse saturable absorption of 2D Te NSs is derived from faster exciton relaxation and stronger excited state absorption. This work paves the way for the design of saturable absorbers with high performance and broadens the application of 2D Te in the field of laser protection and other novel ultrafast photonics.

2D materials towards ultrafast photonic applications

Two-dimensional materials are now excelling in yet another arena of ultrafast photonics, including optical modulation through optical limiting/mode-locking, photodetectors, optical communications, integrated miniaturized all-optical devices, etc.