A nonlinear optical crystal with deep-ultraviolet transparency and appropriate birefringence achieved using π-conjugated confined [BOF(OH)]

• Published in: New journal of chemistry 2024-09, Vol.48 (35), p.15281-15286
• Main Authors: Ouyang, Tao, Chen, Xu, Chen, Shanshan, Li, Yanqiang, Shang, Xiaoying, Bai, Zhiyong, Jiang, Ningtao, Yan, Zhishuo, Luo, Junhua, Zhao, Sangen
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d4nj02834a

Finding a deep-ultraviolet (deep-UV, λ < 200 nm) nonlinear optical (NLO) crystal is vital to a number of advanced optical technologies, yet it remains a great challenge. Herein, we report a deep-UV NLO crystal, K 2 B 3 O 3 F 4 (OH) (KBOFH), composed of π-conjugated confined groups. It exhibits a relatively large birefringence of 0.054@550 nm and a wide transparency window with an absorption edge below 200 nm. Theoretical calculations reveal that the observed optical properties of KBOFH originate from the confined π-conjugated [B 3 O 3 F 4 (OH)] unit, in which the π-conjugated interactions are decoupled by the tetrahedral non-π-conjugated [BO 2 F 2 ] unit. This work provides an opportunity to design deep-UV NLO crystals containing π-conjugated confined groups. Based on a π-conjugated confinement strategy, we designed and synthesized a deep-UV NLO crystal, K 2 B 3 O 3 F 4 (OH), exhibiting a moderate birefringence (0.054@550 nm) and deep-UV transparency (