Synthesis And Third Order Nonlinear Optical Properties Of Nickel Molybdate/Carbon Nanotubes Composites

The rapid development of science and technology in current era has promoted the research progress of nonlinear optics.The exploration of new nonlinear optical materials has become a hot research topic.Molybdate（MMo O₄）materials possess excellent physical and chemical properties.The internal crystal structure of molybdate is relatively diverse,and molybdenum possesses more chemical valence states.Therefore,MMo O₄ has become the focual attention of researchers.Furthermore,the reserves of molybdate in my country are very rich,accounting for about 44%of the global molybdenum sources.The deep development of molybdate materials provideds certain strategic significance.This paper mainly focuses on nickel molybdate（Ni Mo O₄）and carbon nanotubes（CNTs）material as the research objects.Then the third-order nonlinear optical properties of Ni Mo O₄ and Ni Mo O₄/CNTs composite were explored.The main research contents are as follows:Herein,nickel chloride,ammonium molybdate and carbon nanotubes were used as raw materials.The Ni Mo O₄ material and Ni Mo O₄/CNTs composite were prepared by hydrothermal method and solution blending method,respectively.Next,the morphology of the material is characterized and analyzed by Scanning electron microscopy,Raman spectroscopy and X-ray diffraction.The morphology of the Ni Mo O₄ material is an irregular flake structure.The Ni Mo O₄/CNTs composite exists in the form of flakes and rods.The above two materials are both micron-sized particles.Next,the Ni Mo O_4/PMMA and（Ni Mo O₄/CNTs）/PMMA were prepared by constant temperature water bath method.The linear optical properties of the samples were analyzed by UV-vis spectrometer.The results show that the samples are uniformly dispersed and display good light transmittance.The nonlinear optical properties of the Ni Mo O_4/PMMA and（Ni Mo O₄/CNTs）/PMMA were measured by Z-scan technique.（1）The open-aperture（OA）Z-scan experimental results indicate that Ni Mo O_4/PMMA shows typical saturable absorption（SA）properties.The SA effect enhances with the increase of incident energy.It can be attributed to the unique flake structure and thermo-optical effect of Ni Mo O₄ material.The（Ni Mo O₄/CNTs）/PMMA organic glass shows typical reverse saturable absorption（RSA）properties.As the incident energy increases from 30μJ to 60μJ,the valley value of the curve becomes lower and lower,from 0.59 to 0.32.The RSA effect enhances with the increase of incident energy,which can be attributed to the competitive effect between Ni Mo O₄ and CNTs.（2）The closed-aperture（CA）Z-scan experimental results indicate that Ni Mo O_4/PMMA shows typical self-focusing effect.The nonlinear refraction coefficientγ=9.73×10^-4 cm² GW^-1.The（Ni Mo O₄/CNTs）/PMMA organic glass shows typical self-defocusing effect,andγ=-1.07×10^-3 cm² GW^-1.（3）Finally,the optical limiting（OL）properties of（Ni Mo O₄/CNTs）/PMMA is analyzed.The results show that the optical limiting threshold（Fth）and normalized transmittance clamp value（Tc）of（Ni Mo O₄/CNTs）/PMMA organic glass are 0.83 J cm^-2 and 0.48,respectively.In summary,Ni Mo O₄ material and Ni Mo O₄/CNTs composite possess excellent nonlinear optical properties and show potential application value in the fields of optical switches and laser protection.