Fig. 2: Optical anisotropy of MoS₂.

a Real (n) and imaginary (k) parts of the dielectric function along the ab-plane and c-axis. b Comparison of the MoS₂ refractive index along the ab-plane with other high-refractive-index materials commonly used in nanophotonics^31,32,33. The inset compares the ratio of the crystal parameters (c and a in Fig. 1a) versus the distance between the neighboring chalcogens (S, Se, and Te) for various TMDCs. The highest anisotropy is expected for TMDCs denoted by red circles. The crystallographic data were adopted from the review article⁴⁸. c Comparison of the absolute birefringence values of MoS₂ with different birefringent materials, including h-BN and BaTiS₃, reported showing the highest anisotropy so far. The birefringence values for other materials in c were adopted from several reports^{5,6,7,8,9,10,11}.