Study On The Third-order Nonlinear Optical Properties Of Two-dimensional Layered Germanium Selenide And Germanium Sulfide Materials

The all-optical signal processing device is the basic optical device in the all-optical communication network,which is crucial in the construction of all-optical networks in the future.The physical basis of the all-optical signal processing device is the nonlinear optics of the material.Among them,two typical"light-controlled"all-optical processing devices,all-optical thresholders and all-optical wavelength converters,are based on three materials.First-order nonlinear optical absorption characteristics and four-wave mixing of materials(ie,third-order nonlinear optical refractive index).In recent years,the discovery of various new two-dimensional materials and the exploration and application of their remarkable nonlinear optical properties have provided the possibility for the development of all-optical devices and the realization of micro-integration.In particular,two-dimensional materials with excellent third-order nonlinear absorptivity or nonlinear refractive index have very high applications and requirements in all-optical signal processing.Therefore,the search and preparation of third-order nonlinear materials has always been a focus of nonlinear optics research.In this paper systematically studies the third-order nonlinear optics of two-dimensional layered germanium selenide and germanium sulfide materials.We prepared a few layers of germanium selenide(GeSe)nanoplates by liquid phase exfoliation,and characterized their basic properties such as absorption and morphology.The open-aperture Z-scan technology was used to measure its absorption characteristics in the femtosecond 400nm,800nm,and 1064nm bands.The results show that the GeSe nanoplates have obvious broadband saturated absorption characteristics in the visible and near infrared bands.In order to further determine the influence of the pulse width of the incident beam on its saturation absorption characteristics,three different pulse width(7ns,10ps,56fs)lasers were used as the excitation light source for the measurement in the 1064nm band.The results show that under the excitation of light sources with different pulse widths,the measured nonlinear absorption coefficients of the samples have a significant pulse width dependence.The ultrafast carrier dynamics of GeSe nanoplates was experimentally studied.By fitting the experimental data,we know that the fast and slow relaxation times at different wavelengths of 800,871,1064,and 1100 nm are about 0.54-1.08 ps and 52.4-167.2 ps,respectively.The significant ultrafast NLO properties of GeSe nanoplates imply their potential in the development of nanophotonic devices.Here,we designed and fabricated the all-optical diode by means of the GeSe/C₆₀ tandem structure and demonstrated that the saturable absorption behavior of GeSe NPs can be used to fabricate a photonic diode,which exhibits nonreciprocal transmission of light similar to that of an electron diode.In this paper,GeS nanoplates dispersions were prepared by dissolving bulk GeS crystals in ethanol solvent and using liquid-phase exfoliation method,and the nonlinear absorption characteristics of GeS in the femtosecond 400nm and 800nm bands were studied by the aperture Z-scan technique.Characterized its broadband saturation absorption characteristics in the visible to near infrared band.SSPM technique was used to measure the nonlinear refractive index(n₂?10^-6 cm²/W)of GeS.nanoplates.