K 0.9 Rb 2.1 B 8 PO 16 : Design and Synthesis of a Deep-Ultraviolet Nonlinear Optical Crystal with Balanced Performance Derived from π-Conjugated and Non-π-Conjugated Groups

作者：Wenyu He, Xianchao Zhu, Zhanggui Hu, Jiyang Wang, Yicheng Wu · 发表于：Inorganic Chemistry · 年份：2024 · DOI：10.1021/acs.inorgchem.4c03422 · 被引用次数：10 · 研究领域：Crystal Structures and Properties、Solid-state spectroscopy and crystallography、Photorefractive and Nonlinear Optics

A new deep-ultraviolet (DUV) nonlinear optical (NLO) material K 0.9 Rb 2.1 B 8 PO 16 (KRBPO) has been designed and synthesized by adjusting the B/P molar ratio to 8:1. The KRBPO crystals were synthesized by a flux method and crystallized in noncentrosymmetric (NCS) and polar space group Cc. This compound exhibits a double-layer structure in which the A layer is composed of [B 2 O 5 ] and [BO 4 ] units and the B layer is formed by interconnected [B 3 O 7 ] and [BO 3 ] groups, and the two layers are connected by [PO 4 ] tetrahedron. The theoretical calculations and experiments show that the synergistic interaction of π-conjugated and non-π-conjugated units leads to relatively well-balanced NLO properties of the title compound, including moderated SHG (0.7 × KDP), short UV cutoff edge (λ cutoff < 190 nm), and a large band gap of 6.16 eV. Specifically, the coplanar arrangement of B–O groups in double-layer makes the KRBPO display a large birefringence (0.075@532 nm) and enables the shortest phase-matched wavelength to reach an important laser output wavelength of 266 nm.