Synthesis,Characterization And Second-Order Nonlinear Optical Property Of Dual Structural-Unit Compounds Containing Chalcogen Element

Nonlinear optical(NLO)materials are important functional materials,which can convert the frequencies of lasers,and they have been widely applied in the fields of laser communications,laser weapons,laser processing,and laser storage.Second-order nonlinear optical crystal is a kind of materials that can double the frequencies of lasers.The existed benchmarked second-order NLO crystals cannot meet the market demands for their several disadvantages such as weak second-order nonlinear effect,low laser damage threshold,and narrow transparent window.However,those NLO crystals contains chalcogen elements usually have large NLO coefficients and wide transparent windows.Besides,among those compounds contains two structural units are more possible to show second-order nonlinear optical property.Therefore,it is quite necessary to investigate and search for novel second-order NLO crystals to replace available commercialized crystals.To solve these problems,this thesis includes the following three work:1.This work has obtained a novel chalcogenide borate YSeBO2 via high temperature solid-state method,and it is the second selenide borate that has been reported so far.The transparent rod-like YSeBO2 crystals crystallize in noncentrosymmetric space group Cmc21(No.36),and have novel structural type.The crystal structure of YSeBO2 is consist of two structural units,which are[BO3]3-planar triangle and[YO3Se4]11-pentagonal bipyramid,and features the[YSeBO2]n planar belt.Second-order nonlinear optical measurement shows that the SHG intensity of YSeBO2 powder sample is around 1/6 that of KDP,and it also depicts phase-matchable ability under the irradiation of 1064 nm laser.The UV-Vis-NIR diffuse reflectant spectrum shows this compound has an optical energy gap of 3.45 eV.DFT calculations is also performed addressing the electronic structure and nonlinear optical property.2.This work has synthesized two isostructural chalcogenide adducts CHI3·(S8)3 and ASI3·(S8)3 successfully by a solution evaporation method.These two compounds are both crystallized in noncentrosymmetric space group R3m,featuring van der Waals interaction linked CHI3 tetrahedra or SbI3 trigonal pyramids with crown-like S8 molecules.Second-order nonlinear optical measurement shows that SHG intensities of CHI3·(S8)3 and ASI3·(S8)3 are 5.1 and 2.0 times that of KDP under the irradiation of 1064 um laser,respectively,and 0.7 and 0.8 times that of AGS under irradiation of 2100 um laser,respectively.Both two adducts show phase-matchable behavior under laser irradiations with two kinds of wavelengths.LIDT measurement shows that the LIDT values of CHI3·(S8)3 and AsI3·(S8)3 are 15 and 51 times that of AGS crystals.The theoretical calculation depicts that CHI3 tetrahedra and AsI3 pyramid trigonal structural units make mainly contributions to their SHG intensities respectively in two compounds.3.This work has synthesized a pentanary chloride sulfate KBiCl2SO4 via solution evaporation method,and it is crystallized in noncentrosymmetric space group P212121(No.19)The crystal structure of KBiCl2SO4 features a {[BiCl2(SO4)]-}? chain along the polar axis,which is consist of[BiCl2O3]5-polyhedral and[SO4]2-tetrahedral structural units.Second-order nonlinear optical measurement show that SHG intensity of KBiCl2SO4 crystals is 1.7 times that of KDP under the irradiation of 1064 nm laser,and it is phase-matchable.UV diffuse reflectant spectrum measurement depicts that the optical energy gap of KBiclSO4 is 3.95 eV,and theoretical calculation results demonstrate that both two structural units make contributions to its SHG effect.