For many years much research interest has been focused on borates for the exploration of nonlinear optical materials. The success of these materials can be attributed to the unique structural characteristics of boron-oxygen groups with planar BO3 and tetrahedral BO4 groups as the basic structures which can form NLO-active anionic groups. In borates, the B-O covalent bonds have no absorption in UV region owing to their large covalent bond energy. The borates generally have high damage thresholds since they are wide band-gap materials. In addition, the alkali metal-oxygen bond is ideal for the transmission of UV light because there are no d-d electron transitions in this range.

　　Prof. Shilie Pan and his Ph.D. students from Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, recently made great progress in the prediction and design of new nonlinear optical materials, a novel UV NLO material Li3Cs2B5O10 is developed for the first time.Optical characterization of the Li3Cs2B5O10 crystal indicates that it possesses a UV cut off edge at 175 nm and is phase-matchable. Of particular merit, Li3Cs2B5O10 grows from its stoichiometric ratio and melts at exceptionally fast rates. The combined features of phase matching, congruently melting and a short wavelength UV cut off edge are important for advanced laser applications.The article “A congruently melting and deep UV nonlinear optical material: Li₃Cs₂B₅O₁₀” (Journal of Material Chemistry，2011, 21 (9), 2890–2894) has been identified as a ‘hot article’ for Journal of Materials Chemistry. It has been highlighted on the blog (http://blogs.rsc.org/jm/).

　　The work has been supported by Chinese Academy of Sciences, the National Natural Science Foundation of China.