Mg₃B₇O₁₃Cl: A New Quasi‐Phase Matching Crystal in the Deep‐Ultraviolet Region

Abstract Deep‐ultraviolet lasers play an important role in many scientific and technical fields, the generation of which by means of the nonlinear optical frequency conversion technology attracted immense research interest over the past few decades. Up to now, there are few nonlinear optical crystals, except KBe₂BO₃F₂, which could produce deep‐ultraviolet coherent light by a harmonic generation process. However, industrialization of KBe₂BO₃F₂ is hampered by its layering growth habit and weak interlayer force. Here, a new deep‐ultraviolet nonlinear optical crystal, Mg₃B₇O₁₃Cl, is found, which will be a good candidate for deep‐ultraviolet coherent generation. It crystallizes an acentric space group of Pca2₁ at room temperature with both 3D borate frameworks and distorted octahedrons, which makes it a unity of optical nonlinearity and ferroelectricity. Furthermore, a short absorption cutoff of 155 nm, a second harmonic generation coefficient of 0.38 pm V⁻¹, a coercive field of 21.2 kV cm⁻¹, and a remanent polarization of 0.36 µC cm⁻² for Mg₃B₇O₁₃Cl crystal are identified. These features indicate that Mg₃B₇O₁₃Cl crystal can generate deep‐ultraviolet coherent light by a quasi‐phase matching technique with a periodically poling method. This pioneering and profound work points out a new research area in the development of deep‐ultraviolet lasers.