Balancing the key performance metrics,such as a large second harmonic generation(SHG)response and a wide band gap,is an extremely important but intractable challenge for the development of infrared(IR)nonlinear optica...Balancing the key performance metrics,such as a large second harmonic generation(SHG)response and a wide band gap,is an extremely important but intractable challenge for the development of infrared(IR)nonlinear optical(NLO)materials.Herein,we report two new polymorphs of BaGa_(4)S_(7),β-andγ-BaGa_(4)S_(7),both of which crystallize in the noncentrosymmetric and polar space groups,Pmc2_(1)(No.26)forβ-BaGa_(4)S_(7)and Cm(No.8)forγ-BaGa_(4)S_(7).They show an interesting structural evolution from AA’[Ga_(6)S_(16)]_(∞)chains to AA’A’A[Ga_(6)S_(16)]_(∞)chains to AAA’AAA’[Ga_(6)S_(16)]_(∞)chains as their structures show a tran-sition from the high-temperature phase to the low-temperature phase.More importantly,they both exhibit excellent NLO properties.In particular,β-BaGa_(4)S_(7)exhibits the best balance along with a large phase-matching SHG response(1.2×AgGaS_(2))and a wide band gap(3.94 eV).These indicate thatβ-BaGa_(4)S_(7)will be a promising IR NLO crystal for high-power laser application.The research also provides an insight into exploring new IR NLO crystals based on structural rearrangement.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52172006,22071179,51972230,51890864 and 51890865)the Natural Science Foundation of Tianjin(Grant No.20JCJQJC00060 and 21JCJQJC00090).
文摘Balancing the key performance metrics,such as a large second harmonic generation(SHG)response and a wide band gap,is an extremely important but intractable challenge for the development of infrared(IR)nonlinear optical(NLO)materials.Herein,we report two new polymorphs of BaGa_(4)S_(7),β-andγ-BaGa_(4)S_(7),both of which crystallize in the noncentrosymmetric and polar space groups,Pmc2_(1)(No.26)forβ-BaGa_(4)S_(7)and Cm(No.8)forγ-BaGa_(4)S_(7).They show an interesting structural evolution from AA’[Ga_(6)S_(16)]_(∞)chains to AA’A’A[Ga_(6)S_(16)]_(∞)chains to AAA’AAA’[Ga_(6)S_(16)]_(∞)chains as their structures show a tran-sition from the high-temperature phase to the low-temperature phase.More importantly,they both exhibit excellent NLO properties.In particular,β-BaGa_(4)S_(7)exhibits the best balance along with a large phase-matching SHG response(1.2×AgGaS_(2))and a wide band gap(3.94 eV).These indicate thatβ-BaGa_(4)S_(7)will be a promising IR NLO crystal for high-power laser application.The research also provides an insight into exploring new IR NLO crystals based on structural rearrangement.
