Synthesis And Characterization Of Infrared Nonlinear Optical Crystals Of Oxychalcogenides

3?5?m and 8?12?m mid-infrared laser have important application value in industrial and civil fields such as molecular spectroscopy,remote sensing,free communication and environmental monitoring.Using the frequency conversion technology of nonlinear optical crystals,such as optical parametric oscillation and optical parametric amplification,is an effective way for solid-state lasers to produce medium and far-infrared coherent light.In this paper,four new oxychalcogenides crystals with non-centrosymmetric structure and nonlinear optical effect are designed and synthesized by combining oxides and chalcogenides.Their small size single crystals were obtained,and their crystal structures were determined by single crystal diffraction.Further,their optical properties,nonlinear optical properties and thermal properties are systematically studied.Specifically include:1.Sr₂Zn Sn₂OS₆and Ba₂Zn Sn₂OS₆:two new oxychalcogenides with melilite-type structure;Using the classical structure A₂BC₂O₇(A=Ba,Sr;B=Zn,Cd,Hg;C=Ga,Si,Ge)of melilite-type family as template,two new oxychalcogenides,Sr₂Zn Sn₂OS₆and Ba₂Zn Sn₂OS₆,were successfully synthesized by partially replacing the oxygen element in the structure with sulfur element and introducing heavier Sn element.They all crystallize in a non-centrosymmetric P42₁m space group.UV diffuse reflectance spectra show that Sr₂Zn Sn₂OS₆and Ba₂Zn Sn₂OS₆have large optical band gaps of3.52 and 3.50 e V,respectively;The infrared spectrum shows that they have a wide transmission range(3.5?15.5?m);And their SHG responses are 0.6 and 0.7 times Ag Ga S₂respectively.Type I phase matching can be realized under the laser with wavelength of 2090 nm.These performances show that Sr₂Zn Sn₂OS₆and Ba₂Zn Sn₂OS₆are two potential medium and far infrared nonlinear optical crystal materials.2.Sr₃Sn(CO₃)OSe₃:the first polyanion complex oxychalcogenides containing planar CO₃;By further introducing CO₃groups with planar configuration into the oxygen-sulfur system,the first oxychalcogenide—Sr₃Sn(CO₃)OSe₃with tetrahedral and planar configuration was successfully designed and synthesized.The compound crystallizes in the non-centrosymmetric Pmn2₁space group.Property measurement shows that it exhibits a wide optical band gap(3.46 e V)and an appropriate birefringence index(0.13@2090 nm).The synthesis of Sr₃Sn(CO₃)OSe₃provides a new material system for the structural design of new infrared nonlinear optical crystals.3.Synthesis,structure and properties of other compounds.In the above research work,we also obtained some other new crystals,including centrosymmetric oxychalcogenide Ba Ge₂O₃S₂and non-centrosymmetric sulfide Ba Zn Ge S₄.Among them,Ba Zn Ge S₄crystallizes in Fdd2 space group,which can show nonlinear optical properties.It is a potential mid-infrared nonlinear optical crystal.Although Ba Ge₂O₃S₂crystallizes in a centrosymmetric space group and cannot exhibit nonlinear optical properties,there are few studies on this kind of oxychalcogenides at present.The study on its synthesis,structure and structure-property relationship will help people to understand this kind of compound.