Strong Nonlinearity Induced by Coaxial Alignment of Polar Chain and Dense [BO ] Units in CaZn (BO ).

Discovery of new efficient nonlinear optical (NLO) materials with large second-order nonlinearity for the short-wave ultraviolet spectral region (λ ≤266 nm, PM=phase-matching) is still very challenging. Herein, a new beryllium-free borate CaZn (BO ) with Sr Be B O (SBBO) double-layered like configuration was rationally designed, which not only preserves the structural merits but also eliminates the limitations of the SBBO crystal. CaZn (BO ) shows a large PM second harmonic generation (SHG) reponse of 3.8×KDP, which is 38 times higher than that of its barium analogue. This enhancement mainly originates from the [Zn O ] polar chains with a large net dipole moment and [BO ] units with a high NLO active density. Our findings show the great significance of the [ZnO ] tetrahedra introduced strategy to design beryllium-free SBBO-type NLO crystals and also verify the feasibility of using simple non-isomorphic substitution to induce giant second-order nonlinearity enhancement.