Design of a new ultraviolet nonlinear optical material KNO3SO3NH3 exhibiting an unexpected strong second harmonic generation response

Based on the co-crystal engineering strategy, a new polar non-centrosymmetric compound, KNO3SO3NH3, was meticulously designed by introducing KNO3 into the centrosymmetric SO3NH3 crystal. It has an unexpected strong second-harmonic generation (SHG) response (10 x KDP), which is a new record among the inorganic nonlinear optical (NLO) materials without NLO-active cations. Theoretical calculations showed that the enhanced SHG response should be attributed to the effect of hydrogen bond. Meanwhile, it has the shortest absorption edge of 216 nm among the known materials with strong SHG responses (>8 x KDP). Besides, it possesses a large birefringence of 0.096@546 nm. Our results showed that KNO3SO3NH3 should be an excellent UV NLO crystal.