A3Sc(SO4)3 (A = K, Rb, Cs): Three Deep‐Ultraviolet Transparent Alkali‐Scandium Sulfates with Strong Second‐Harmonic Generation Response and High Thermal Stability

Abstract Nonlinear optical (NLO) crystals that have the capability of achieving tunable lasers through frequency conversion are of great importance in solid‐state lasers. Herein, three new deep‐UV transparent alkali‐scandium sulfates with strong second‐harmonic generation (SHG) response and high thermal stability, A 3 Sc(SO 4 ) 3 (A = K, Rb, Cs), are successfully obtained. It is interesting that the slightly distorted [ScO 6 ] octahedrons are in an ordered/oriented arrangement, which is in favor of the generation of SHG response. Especially, K 3 Sc(SO 4 ) 3 not only exhibits a strong phase‐matching SHG response of 1.6 × KDP, a short deep‐ultraviolet (deep‐UV) cutoff edge of 190 nm, a wide transparent window covering from the deep‐UV region to mid IR, a high laser‐induced damage threshold of 165 MW cm −2 and easy growth of large single crystal, but also behaves thermal stable up to 900 °C under an air atmosphere. Crystal structures and theoretical calculations reveal that their strong SHG responses mainly stem from the slightly distorted [ScO 6 ] octahedron. This study highlights A 3 Sc(SO 4 ) 3 (A = K, Rb, Cs) as promising deep‐UV transparent NLO crystals and offers a new approach for the pursuit of high‐performance NLO crystals.