Figure 1: Schematic of a Veselago lens in the x-z plane.
From: Veselago lensing with ultracold atoms in an optical lattice
A diverging pencil of rays is focused upon entry into a medium with refractive index n=−1 by negative refraction. The negative refraction can be described by Snell’s law when noting that the refractive index at the surface changes sign from positive to negative.
