Large nonlinear optical effect in tungsten bronze structures via Li/Na cross-substitutions

By a simple cross-substitution of A-site Li/Na in tetragonal tungsten bronze (TTB) structures, we successfully synthesized a new niobate compound, Pb-2.15(Li0.25Na0.75)(0.7)Nb5O15, with a (2 root 2a(TTB), root 2b(TTB), 2c(TTB)) superstructure. This compound exhibits a strong second harmonic generation (SHG) up to similar to 47 x KDP. The large SHG response is related to strengthened local distortion, manifesting cross-substitution as a possibly general route to improve the NLO effect in stiff and low symmetric structures.