A beryllium-free deep-UV nonlinear optical material CsNaMgP2O7 with honeycomb-like topological layers

Abstract

Few nonlinear optical (NLO) materials are available for deep-UV second-harmonic generation (SHG), limited by the fundamental requirements of the structure-directing optical properties. KBe₂BO₃F₂ is the sole exception, but it suffers from the high toxicity of the compositional beryllium element and a serious layering growth tendency. Here, we report a beryllium-free deep-UV NLO phosphate with honeycomb-like topological structural layers, namely, CsNaMgP₂O₇. The phosphate exhibits an enhanced SHG response of 1.1 times that of KH₂PO₄, which is comparable to that of KBe₂BO₃F₂. Based on theoretical analysis, the enhanced SHG response can be well rationalized. Meanwhile, CsNaMgP₂O₇ possesses a reinforced interlayer bonding of about 2.95 times that of KBe₂BO₃F₂, which is very favorable to mitigate the layering growth tendency. This work will be helpful to better understand the structure–property relationships in deep-UV NLO materials.