Clamping effect driven design and fabrication of new infrared birefringent materials with large optical anisotropy

Infrared (IR) birefringent materials with large optical anisotropy and wide transparency range are important for efficient light manipulation in various IR optical devices. Herein, two new IR birefringent materials AMgGeSe 3 (A = Li, Na) with large optical anisotropy were rationally designed by a rigid octahedron and flexible dimer combined strategy and fabricated in experiment. The introduction of rigid [LiSe 6 ]/[NaSe 6 ] and [MgSe 6 ] octahedra effectively regulates the geometry and arrangement of the flexible [Ge 2 Se 6 ] dimers, resulting in the birefringence as large as 0.334@1,064 nm in LiMgGeSe 3 and 0.445@1,064 nm (the largest one in the reported [Ge 2 Se 6 ] dimer-contained selenides) in NaMgGeSe 3 . Density functional theory (DFT) calculations and statistical analyses highlight the influence of polarizability anisotropy, density, arrangement of units, as well as layer distance on birefringence. The results indicate that AMgGeSe 3 (A = Li, Na) crystals are the promising IR birefringent materials and it gives an insight into the exploration of new IR birefringent materials with large birefringence based on the clamping effect from rigid groups.