K<sub>5</sub>Mg<sub>2</sub>La<sub>3</sub>(BO<sub>3</sub>)<sub>6</sub>: An Efficient, Deep-Ultraviolet Nonlinear Optical Material
Runqing Liu, Hongping Wu, Hongwei Yu, Zhanggui Hu, Jiyang Wang, Yicheng Wu
Abstract
KBe2BO3F2 (KBBF) is the sole nonlinear optical (NLO) crystal that can practically generate deep-ultraviolet (UV) coherent light by a direct second-harmonic generation (SHG) process. However, the toxic BeO and crystal layer habit limit its application. With this background, a new beryllium-free borate, K5Mg2La3(BO3)6 (KMLBO), has been designed and synthesized through a high-temperature solution method. KMLBO crystallizes into the noncentrosymmetric space group P31m (No. 157) and features a three-dimensional framework structure consisting of alveolate [LaBO3]∞ layers further tightly bound via interlayer [BO3]3– groups. KMLBO not only exhibits desirable performances including deep-UV transparency, large SHG (∼3.1 × KH2PO4), and phase-matchability but also overcomes the crystal layer habit of KBBF, demonstrating that it is a potential deep-UV NLO crystal.