Ultraviolet Crystal with Strong Optical Nonlinearity by Creating Halogen-Centered Secondary Building Blocks

Designing new ultraviolet nonlinear optical (NLO) crystalswithstrong second-harmonic generation (SHG) response and a deep ultravioletcutoff edge is an unremitting pursuit of scientific researchers, accompaniedby the key issues of how to realize a noncentrosymmetric structurewith the ideal arrangement of ultraviolet NLO-active genes. Herein,a strategy that creates halogen-centered secondary building blockswith rare-earth atoms was used for further design, and we synthesizedrationally an unprecedented NLO crystal Cs2La2B10O17Cl4 exhibiting the largestSHG response (2.1 x KDP) among borates with [B5O11] as the fundamental building blocks. The unique role ofCl-centered secondary building blocks in regulating the arrangementof the B-O framework and enhancing nonlinearity was discussedin detail, which will bring the researcher a perspective in designingnew NLO crystals.