Rational design of birefringent materials

Birefringence (Δn) is the dependence of the refractive index on the polarization of light travelling through a material. Birefringent materials are used as polarizers, waveplates and for other novel light-matter coupling. While many birefringent materials have been reported from visible (e.g., Δn = 0.17 in calcite) to mid-infrared (e.g., Δn ~2.1 in Sr_9/8TiS₃), the origins of large birefringence across the different classes of  materials, are poorly understood, which in turn precludes rational design of materials with desired combination of birefringence and wavelength. We will present design rules for identifying materials with large birefringence, and in conjunction with screening of materials databases and first-principles electronic structure calculations, we will list promising birefringent materials. We then use the identified design rules to explore candidates in a vast compositional space, including oxides, sulfides, nitrides, chlorides, fluorides, and phosphates with different polyhedral connectivity. We will end with a discussion of representative birefringent compounds for each wavelength region from UV to IR.

This work was supported by NSF through DMR-2122070, DMR-2122071 and DMR-2145797 and an ARO MURI grant # W911NF-21-1-0327.