The chemical-electronic structures of functional modules and their spatial arrangement mainly determine the functional performance of materials.Tetrahedral structural units in borates can be used to widen the band gap...The chemical-electronic structures of functional modules and their spatial arrangement mainly determine the functional performance of materials.Tetrahedral structural units in borates can be used to widen the band gap for designing deep-ultraviolet/ultraviolet(UV)nonlinear optical(NLO)materials,but they are rarely favored due to their weak optical nonlinearity.In this study,we investigate the second-harmonic generation(SHG)response of LiGeBO_(4) with a combined experimental and computational approach.LiGeBO_(4) achieves a balance between a large band gap(6.2 eV)and a strong SHG coefficient(double that of KH_(2)PO_(4)(KDP)),which rarely exists in tetrahedral-based crystals.The origin of the SHG effect in LiGeBO_(4) is analyzed in detail using density functional theory(DFT)calculations.The calculated frequency dependent SHG efficiency of LiGeBO_(4) is 1.1 pm V^(−1),which is in accordance with the experimental value.Based on the modern polarization theory,the nonlinear electronic polarization induced by an external electric field along the[001]direction is about 4 pm V^(−1),which indicates the SHG susceptibility is 2 pm V^(−1) along the z-direction.Moreover,the SHG-density result shows that the SHG effect of LiGeBO_(4) mostly comes from the Ge–B–O tetrahedral units.展开更多
基金supported by the Western Light Foundation of CAS(Grant No.2017-XBQNXZ-B-006)the Shanghai Cooperation Organization Science and Technology Partnership Program(Grant No.2017E01013)+2 种基金the National Natural Science Foundation of China(Grant No.11774414,11474353)the Tianshan Innovation Team Program(Grant No.2018D14001)support from the“Fujian Institute of Innovation,Chinese Academy of Sciences”(Grant No.FJCXY18010202).
文摘The chemical-electronic structures of functional modules and their spatial arrangement mainly determine the functional performance of materials.Tetrahedral structural units in borates can be used to widen the band gap for designing deep-ultraviolet/ultraviolet(UV)nonlinear optical(NLO)materials,but they are rarely favored due to their weak optical nonlinearity.In this study,we investigate the second-harmonic generation(SHG)response of LiGeBO_(4) with a combined experimental and computational approach.LiGeBO_(4) achieves a balance between a large band gap(6.2 eV)and a strong SHG coefficient(double that of KH_(2)PO_(4)(KDP)),which rarely exists in tetrahedral-based crystals.The origin of the SHG effect in LiGeBO_(4) is analyzed in detail using density functional theory(DFT)calculations.The calculated frequency dependent SHG efficiency of LiGeBO_(4) is 1.1 pm V^(−1),which is in accordance with the experimental value.Based on the modern polarization theory,the nonlinear electronic polarization induced by an external electric field along the[001]direction is about 4 pm V^(−1),which indicates the SHG susceptibility is 2 pm V^(−1) along the z-direction.Moreover,the SHG-density result shows that the SHG effect of LiGeBO_(4) mostly comes from the Ge–B–O tetrahedral units.
