ABi2(IO3)2F5 (A= K, Rb and Cs): Combination of Halide and Oxide Anionic Units to Create Large SHG Response with Wide Bandgap

A family of nonlinear optical materials that contain the halide, oxide and oxyhalide polar units simultaneously in a single structure, namely, ABi2(IO3)2F5 (A = K, 1;Rb,2 and Cs,3), have been designed and synthesized. They crystallize in the same polar space group of P21 with a two-dimensional double-layered framework constructed by [BiF5]2- and [BiO2F4]5- units connected to each other by four F atoms, in which two [IO3]- groups are linked to [BiO2F4]5- unit on the same side, and a hanging Bi-F bond of [BiF5]2- unit is located on the other side via ionic interaction with the layer-inserted alkali metal ions to form three-dimensional structure. The well-ordered alignments of these polar units lead to a very strong second harmonic generation response of 12 (1), 9.5 (2) and 7.5 (3) times larger than that of KDP under 1064 nm laser radiation. All of them exhibited wide bandgap over 3.75 eV, indicating that they will possess high laser damage threshold.