Non-π-Conjugated Deep-Ultraviolet Nonlinear Optical Crystal K<sub>2</sub>Zn<sub>3</sub>(SO<sub>4</sub>)(HSO<sub>4</sub>)<sub>2</sub>F<sub>4</sub>
Zhou Yang, Xingyu Zhang, Zheyao Xiong, Xifa Long, Yanqiang Li, Yangxin Chen, Xin Chen, Sangen Zhao, Zheshuai Lin, Junhua Luo
Abstract
Deep-ultraviolet (deep-UV) (wavelengths of <200 nm) nonlinear optical (NLO) materials are playing an increasingly important role because of their significant technological applications in advanced scientific instruments. In recent years, the non-π-conjugated systems have received extensive attention as new emerging sources of deep-UV NLO materials. Here, a new non-π-conjugated deep-UV NLO material, K2Zn3(SO4)(HSO4)2F4, has been successfully obtained by the hydrothermal method. It has a layered structure formed by [Zn3(SO4)(HSO4)2F3]∞ layers bridged via K–O and K–F bonds. Powder second-harmonic generation shows that K2Zn3(SO4)(HSO4)2F4 can achieve phase matching, and the response is ∼0.3 times that of KH2PO4. Remarkably, the single-crystal transmittance spectrum confirms that the absorption edge of K2Zn3(SO4)(HSO4)2F4 is below 200 nm, and the experimentally measured birefringence is 0.0126 at λ = 546 nm. In-depth first-principles calculations illustrate well the microscopic origin of the optical properties. This work enriches the structrual diversity of non-π-conjugated deep-UV NLO materials.