A Promising Deep Ultraviolet Nonlinear Optical Crystal Activated by the Ordered Structure Design

Deep-ultraviolet nonlinear optical (DUV NLO) crystals play a vitally important role in many scientific and technological fields, yet their rational design remains an ongoing challenge. Here, through utilizing the ordered structure design, a new KBe2BO3F2-like DUV transparent NLO crystal Cs2KY(B3O6)(2) has been successfully designed and synthesized, in which we first use the largest pi-conjugated B3O6 functional groups to substitute the BO3 to maximize the second-harmonic generation (SHG) response and utilize the K/YO6 connecting groups to replace two BeO3F groups to optimize the layer connections. Eventually, Cs2KY(B3O6)(2) exhibits not only the largest SHG responses in KBe2BO3F2-like DUV borates but also the best growth rate along c axis (the strong layer-habit along c axis has been being the greatest obstacle to prohibit the practical application of KBe2BO3F2 and its derivative). Clearly, the substitution from BO3 triangles to similar topological B3O6 groups and from (BeO3F)(2) groups to similar topological K/YO6 octahedra can better modulate the functional properties of materials in the larger scale. That results in the superior comprehensive properties of Cs2KY(B3O6)(2) and makes it a promising DUV NLO crystal. Therefore, the ordered structure design provides some new insights for assembling the functional and connecting groups to rationally design materials with high-performance.