The centrosymmetric to non-centrosymmetric transformation induced by alkaline-earth cations producing infrared nonlinear optical AeMn6Ga6S16(Ae = Ca, Sr)

Non-centrosymmetric (NCS) structure is an indispensable prerequisite for second-order nonlinear optical (NLO) material. Currently, the mainstream approach for designing new NCS structures still relies on chemical substitution, necessitating an urgent infusion of fresh ideas. In this work, two isomorphic sulfides AeMn6Ga6S16(Ae = Ca, 1; Sr, 2) are afforded by modifying the skeleton of centrosymmetric (CS) Mn2Ga2S5viaintroducing strong electropositive alkaline-earth cations. Concretely, the incorporation of Ca2+/Sr2+cations allows the elementary [MnGaS9]∞chains to reconfigure into bumpy [MnS6]-[GaS4] layers in a new engagement manner, thus enabling the conversion from CS to NCS structure. Such modifications cause not only strong second-harmonic generation (SHG) responses (∼1.5 × benchmark AgGaS2@1,700 nm), but also significantly feasible bandgaps (2.60–2.64 eV) compared to the sulfide Mn2Ga2S5(1.36 eV), which ultimately facilitate ultrahigh laser-induced damage thresholds (4.4–6.6 × AgGaS2@1,064 nm for compounds 1and 2). The present study offers an ingenious approach for the transformation of CS to NCS structure.