Laser damage threshold (LDT) has been considered as a key index, apart from the nonlinear optical (NLO) effect, to characterize the performance of a mid-infrared NLO material. This paper reports and compares the properties of RbIO3 and RbIO2F2 as potential nonlinear optical (NLO) materials to be used in the mid-IR region. RbIO3 is a known compound, and its powder SHG (second harmonic generation) effect is carefully measured in this work for the first time to be as strong as 20 times that of KDP, and its powders show a high damage threshold (LDT) of 125 MW/cm2. In order to investigate the influence on the properties by partially replacing oxygen with fluorine atoms, the new compound RbIO2F2 is synthesized and characterized. Although it also shows relatively strong powder SHG responses 4 times that of KDP, the LDT value of the powders is improved to 156 MW/cm2. The transparent region and the thermal stability of two compounds are also measured with satisfactory results. The electronic structure and the properties of the materials are also investigated by the theoretical approach. All these indicate that RbIO3 and RbIO2F2 are both promising candidates for NLO materials to be used in the mid-IR region and that partially replacing oxygen with fluorine in the molecule can improve the laser damage threshold of the material.

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