Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystal, Tianjin University of Technology, Tianjin 300384, China.
J Am Chem Soc. 2023 Jun 14;145(23):12691-12700. doi: 10.1021/jacs.3c02400. Epub 2023 May 26.
Deep-ultraviolet nonlinear optical (DUV NLO) crystals are indispensable for solid-state lasers to produce coherent light with wavelengths shorter than 200 nm, yet their structure design still faces great challenges because two groups of conflicting properties must be satisfied simultaneously, i.e., "" and "". Clearly, hitherto, no crystal can perfectly satisfy these properties, including KBeBOF. Herein, we design a new mixed-coordinated borophosphate Cs[(BOP)(BO)] (CBPO) by optimizing the matching of cation and anion groups, which unprecedentedly achieves a balance for two groups of contradictions concurrently for the first time. In the structure of CBPO, it has the coplanar and π-conjugated BO groups, which can make it possess a large SHG response (3 × KDP) and large birefringence (0.075@532 nm). Then, terminal O atoms of these BO groups are connected by BO and PO tetrahedra, which eliminates all dangling bonds and blue shifts the UV absorption edge to the DUV region (165 nm). More importantly, owing to the judicious selection of cations, the size of cations and void of anion groups is a perfect match, which makes CBPO possess a very stable three-dimensional anion framework and thus reduces the crystal growth anisotropy A CBPO single crystal with a size of up to 20 × 17 × 8 mm has been successfully grown, through which a DUV coherent light has also been achieved in Be-free DUV NLO crystals for the first time. These indicate CBPO will be the next generation of DUV NLO crystals.
深紫外非线性光学（DUV NLO）晶体对于产生波长小于 200nm 的相干光的固态激光器来说是不可或缺的，但它们的结构设计仍然面临着巨大的挑战，因为必须同时满足两组相互冲突的性质，即“”和“”。显然，迄今为止，没有任何一种晶体能够完美地满足这些性质，包括 KBeBOF。在此，我们通过优化阳离子和阴离子基团的匹配，设计了一种新的混合配位硼磷酸盐 Cs[(BOP)(BO)]（CBPO），它首次前所未有地同时实现了两组矛盾的平衡。在 CBPO 的结构中，它具有共面和π共轭的 BO 基团，这使其具有较大的二次谐波响应（3×KDP）和较大的双折射（0.075@532nm）。然后，这些 BO 基团的末端 O 原子通过 BO 和 PO 四面体连接，消除了所有悬空键，并将 UV 吸收边缘蓝移到深紫外区（165nm）。更重要的是，由于阳离子的合理选择，阳离子的大小和阴离子基团的空隙是完美匹配的，这使得 CBPO 具有非常稳定的三维阴离子骨架，从而降低了晶体生长各向异性。我们已经成功地生长出尺寸高达 20×17×8mm 的 CBPO 单晶，首次在无 Be 的深紫外 NLO 晶体中实现了深紫外相干光。这些表明 CBPO 将成为下一代深紫外 NLO 晶体。
