Rational Design of a Strong Nonlinear Optical Crystal With Ultrawide Bandgap via Fine‐Tuning of Channel Structures
Zi‐Long Geng, Zuju Ma, Rui‐Biao Fu, Xin‐Tao WuABSTRACT
The sustained exploration of non‐centrosymmetric (NCS) structures has unlocked key functionality directly governed by symmetry breaking, including nonlinear optics, ferroelectricity, thermoelectricity and piezoelectricity. Nevertheless, rational and efficient strategies for designing and synthesizing materials with targeted NCS structures remain scarce. Herein, leveraging the structural feature of sulfates in the hexagonal crystal system, we have proposed a flexible channel‐regulation strategy to successfully obtain a new strong hydroxyl‐sulfate nonlinear optical (NLO) crystal with broad deep‐ultraviolet (DUV) transparency window, Li 3 Na 3 Rb(SO 4 ) 3 (OH). Remarkably, it achieves an excellent balance between strong second‐harmonic generation (SHG) response and ultrawide bandgap, such as a strong phase‐matching SHG response of 3.1 × KH 2 PO 4 , an ultrawide bandgap over 6.52 eV corresponding to a DUV cutoff edge below 190 nm and a broad transparency window spanning over 0.19 to 9.20 µm. This result demonstrates that the channel‐regulation strategy offers considerable design flexibility and a wide parameter space.