K2Na(IO3)2(I3O8) with Strong Second Harmonic Generation Response Activated by Two Types of Isolated Iodate Anions

A new alkali metal iodate, K2Na­(IO3)2(I3O8), has been synthesized using the mild hydrothermal method, which is the first example of noncentrosymmetric iodate containing isolated [IO3]− and [I3O8]− groups. To the best of our knowledge, it exhibits the largest second harmonic generation response among the iodates with two types of isolated I–O groups (7.6 × KH2PO4 (KDP) @1064 nm). It also possesses a moderate birefringence (Δn) of 0.055 at 1064 nm for achieving its phase matching and a wide band gap (3.83 eV) for obtaining a high laser damage threshold, which assures that it possesses a high laser-induced damage threshold (LDT, 13 × AgGaS2). These results indicate that it is a good candidate for nonlinear optical applications.