| With the increasing development of high technology,high-energy laser technology is widely used in electronics,communications,medical treatment and other fields.The frequency conversion effect of nonlinear optical(NLO)materials is an important means of extending the tunable harmonic wavelength range of output laser to obtain deep ultraviolet and mid-far infrared lasers.However,the existing commercial nonlinear optical crystals have certain defects that cannot fully meet the actual demand,therefore developing novel nonlinear optical crystal materials is an increasingly urgent demand with the development of laser technology.In this paper,a series of iodate,selenite and telluride compounds were synthesized via hydrothermal methods,their structural analysis and property characterization were performed.The main research contents and results are as follows:1.The highly electronegative fluorine anion was introduced into the d0 transition metal(TM)oxide octahedron,and new types of NLO-active d0 TM oxide-fluoride polyhedra were obtained by incomplete substitution of fluorine for oxygen ligands.These d0 TM oxide-fluoride polyhedra and iodates were used to construct noncentrosymmetric compounds.Two NLO materials,K5(W3O4Fg)IO3(1)and CsZrF4(IO3)(2),were synthesized by hydrothermal method.These two compounds have good comprehensive optical properties,including the frequency doubling effects(11 and 4.5 times that of commercial KH2PO4)and optical band gaps(3.83 and 4.12 eV).In this chapter,the asymmetric oxyfluoride units formed by refractory d0 TM were proved to be beneficial to induce the constouction of noncentrosymmetric structure and obtain a wide optical band gap,which is a new approach for the design of new NLO materials and the optimization of comprehensive performance.2.An novel barium molybdate oxide-fluoride material Ba(MoO2F)2(SeO3)2(3)was obtained by incomplete fluorine substitution of noncentrosymmetric barium molybdate selenite system.Compared with the parent compound,the frequency doubling coefficient and optical band gap of 3 were significantly improved.On this basis,the isomorphic barium molybdate oxide-fluoride tellurite Ba(MoO2F)2(TeO3)2(4)was prepared by substituting Se with the same group of heavy Te,which further increased the frequency doubling coefficient without significantly reducing the band gap,and achieved the purpose of optimizing two key properties at the same time.This work demonstrates the feasibility of multiple substitution methods for optimizing the properties of nonlinear optical materials.3.Pb2(V2O4F)(VO2)(SeO3)3(5)was prepared under hydrothermal conditions.Compound 5 belongs to the chiral space group P212121.The crystal structure of 5 is a three-dimensional framework constructed by three types of vanadium-centered units[VO5F],[VO6]and[VO5]as well as Pb2+ and[SeO3].Studies have shown that the frequency doubling effect of 5 at 1064 nm laser is 0.3 times that of KH2PO4,and the band gap is 2.35 eV.This work provides a noncentrosymmetric preparation method of lead-vanadium oxyfluoride selenite,which has a positive effect on the study of TM oxyfluoride and selenite composite system.4.Three rare earth iodates,Y(IO3)3·H2O(6),Eu(IO3)3·H2O(7)and La2(IO3)6(H2O)(8)were synthesized by hydrothermal method using lanthanide cations with moderate electronegativity as counter ions.Compounds 6 and 7 are isomorphic belonging to the chiral space group P21,and compound 8 belongs to the noncentrosymmetric Pc space group.All three compounds have second-order NLO effects.The frequency doubling effects of compound 6-8 under 1064 nm laser were 3,4.5 and 1.5 times that of KH2PO4,respectively,with phase matching behaviors.The optical band gaps were 4.12,4.36 and 4.24 eV,respectively.The laser damage thresholds were 53,43 and 44 times that of AgGaS2.This work shows that cation regulation can be a new way to the design of second-order NLO materials.5.Two tetravalent ceric iodate phosphates Ce(IO3)3(H2PO4)(9)and Ce(IO3)2(H2PO4)2(10)were prepared by hydrothermal synthesis.Compound 9 is a centrosymmetric structure belonging to the P21/c space group;compound 10 is a noncentrosymmetric structure belonging to the orthorhombic chiral space group P212121.The phase-matched frequency doubling effect of compound 10 measured at 1064 nm laser was 4 times that of KH2PO4.The birefringence was 0.049 and the optical band gap was 2.97 eV.In this study,the differences in crystal structures and symmetry between compounds 9 and 10 induced by the different ratios of[IO3]and[H2PO4]anions,which indicated the feasibility of designing NLO materials via the anion proportion regulation.In the finality,the conclusions and the follow-up research are given. |
PDF Full Text Request