Rational design via dual-site aliovalent substitution leads to an outstanding IR nonlinear optical material with well-balanced comprehensive properties†

Abstract

The acquisition of a non-centrosymmetric (NCS) structure and achieving a nice trade-off between a large energy gap ( E _g > 3.5 eV) and a strong second-harmonic generation (SHG) response ( d _eff > 1.0 × benchmark AgGaS ₂) are two formidable challenges in the design and development of infrared nonlinear optical (IR-NLO) candidates. In this work, a new quaternary NCS sulfide, SrCdSiS ₄, has been rationally designed using the centrosymmetric SrGa ₂S ₄ as the template via a dual-site aliovalent substitution strategy. SrCdSiS ₄ crystallizes in the orthorhombic space group Ama2 (no. 40) and features a unique two-dimensional [CdSiS ₄] ²⁻ layer constructed from corner- and edge-sharing [CdS ₄] and [SiS ₄] basic building units (BBUs). Remarkably, SrCdSiS ₄ displays superior IR-NLO comprehensive performances, and this is the first report on an alkaline-earth metal-based IR-NLO material that breaks through the incompatibility between a large E _g (>3.5 eV) and a strong phase-matching d _eff (>1.0 × AgGaS ₂). In-depth mechanism explorations strongly demonstrate that the synergistic effect of distorted tetrahedral [CdS ₄] and [SiS ₄] BBUs is the main origin of the strong SHG effect and large birefringence. This work not only provides a high-performance IR-NLO candidate, but also offers a feasible chemical design strategy for constructing NCS structures.

Abstract

A new promising IR-NLO material SrCdSiS ₄ with a 2D layered structure has been designed via a dual-site isovalent substitution strategy. Remarkably, it is the first report on an alkaline-earth metal-based IR-NLO material that breaks through the wall of E _g > 3.5 eV and d _eff > 1 × AgGaS ₂.