posted on 2022-12-16, 15:04authored byKejun Bu, Tonghuan Fu, Ziwan Du, Xin Feng, Dong Wang, Zhongyang Li, Songhao Guo, Zongdong Sun, Hui Luo, Gang Liu, Yang Ding, Tianyou Zhai, Qian Li, Xujie Lü
Design
and exploration of high-performance nonlinear optical (NLO)
materials have long been sought with the goal of tunable local structures
and NLO properties for advanced laser technology. Thus far, the design
strategies for second-order NLO materials have been mainly focused
on anionic groups that have made great progress in the development
of new NLO compounds. However, few studies have focused on the effects
of cationic components and their contributions to NLO properties have
long been underappreciated and remain unclear. Here, by introducing
pressure to continuously tune the Cu displacement, we demonstrate
the significant role of the cationic configuration in NLO properties,
and a remarkable enhancement by one order of magnitude in second-harmonic
generation (SHG) has been achieved at 3.4 GPa in thiophosphate CuInP2S6 (CIPS). In situ high-pressure
structural characterization indicates that Cu cations move from the
van der Waals edge to the cages of S6 octahedra during
compression and subsequently form highly distorted [CuS6] octahedra at 3.2 GPa. We quantitively demonstrate the contributions
of cationic displacement on the octahedral distortion and interband
dipole moments, which dominate optical nonlinearity and determine
the enhanced SHG. This work deepens the fundamental understanding
of the relationship between cationic displacement and SHG properties,
thus providing new paths to NLO material design by optimizing the
cationic configurations.