Dimensionality reduction made high-performance mid-infrared nonlinear halide crystal

Abstract Structural dimensionality makes a crucial role in determining electron distribution and corresponding macroscopic optical properties of crystals. Here, we present a new quasi-one-dimensional (1D) halide polymorph NH4HgBr3·H2O (NHB), containing parallel 1D (HgBr3)- chain built from condensed and aligned (HgBr4)2- tetrahedron. The decreased dimensionality reduces the extent of orbital overlap in various directions and leads to band-gap widening. In addition, the quasi-1D structure of NHB results in the high density of states at top valence band and yield a large second harmonic generation (SHG) response (28 × KDP), high laser induced damage threshold (LIDT) (52.7×AGS), and large birefringence value ( 0.183@1064nm ), concurrently. Combining its scalable preparation in solution, NHB is a potential infrared nonlinear optical (NLO) candidate for practical applications. This work demonstrates a successful material design case in halide crystals and highlights dimensionality control as a good strategy in designing better NLO materials.