Development Of Z-scan Measurement System And Measurement Of Nonlinear Optical Properties Of Two-dimensional Materials

With the advancement of science and technology,driven by the demand for ultrafast lasers and optical communication technology,it is especially important to find out a new two-dimensional materials.In order to find two-dimensional materials with greater nonlinear absorption coefficient,nonlinear refractive index and higher modulation depth,nonlinear optical measurement system Z-scan is widely used.As an important member of two-dimensional material,black phosphorus is a popular object.The black phosphorus has the band structure which changes with the layer number and maintains the direct band-gap structure from single-layer to multilayer.It also has the broadband saturable absorption characteristic and is the excellent lock-mode or Q-switched device.In order to find the material that is different from the black phosphorus in some aspects,and to study these materials and to satisfy the testing conditions of different morphological materials,the traditional Z-scan measurement system can not meet our diverse requirements.So it is very important to design a novel functional and diverse measuring system.In this paper,a functional diversity measurement system is designed based on two-dimensional material testing,and the stability and accuracy of the system are verified by different morphological materials such as black phosphorus and bisulfide.Using this system,the nonlinear optical properties of selenium-doped black phosphorus and antimony nanosheets are revealed.The specific research results are summarized as follows:1.Construction of nonlinear optical measuring platform and design of software system.Z-scan technology is a nonlinear optical measurement method based on single beam.In order to get the nonlinear properties of the samples faster and more accurately,we have designed an improved Z-scan measurement light path,and have programmed three sets of control software for the optical path system.Three sets of software are written based on LabVIEW,used for dual-channel Z-scan measurements,three-channel Z-scan measurements and P-scan(power scan)measurements.The three-channel Z-scan measurement software can simultaneously measure the third-order nonlinear real part and imaginary part of the material,and reduce the error caused by the separate measurement.P-scan measurement software for different forms of materials,the results are more reliable,and in turn,the accuracy of the Z-scan measurement system should be verified.2.Ultrafast nonlinear response of selenium-doped black phosphorus and antimony nanosheets.Using liquid phase exfoliation technology,we successfully prepared nanosheets containing a large amount of selenium-doped black phosphorus and studied the ultrafast nonlinear response of the dispersed solution by using the dual-channel Z-scan measurement system and the P-scan measurement system.Third-order nonlinear imaginary part characteristics and saturation strength of the samples were tested under the irradiation of 800 nm femtosecond laser.The results showed that selenium-doped black phosphorus was more saturated than black phosphorus,but the modulation depth was not decreased.Antimony nanosheets were prepared by solvent thermal method,the microstructure characterization and spectral analysis of the dispersed solution show that antimony has achieved high quality dispersion in ethanol solution,and we have used the three-channel Z-scan system to measure the third-order nonlinear real and imaginary parts of antimony nanosheets at the same time under the irradiation of 800 nm femtosecond laser,The P-scan system gets its saturation strength.Third-order nonlinear coefficients and saturation strength of antimony nanosheets irradiated by 1500 nm laser were obtained by using OPA.The results show that the antimony-butadiene is also a very excellent wideband saturable absorbing material,which provides an experimental basis for the mode-locked laser based on antimony.