Glazing with light-concentrating zones by ion exchange

A flat mineral glass comprising a first free surface and a second free surface, wherein the glass comprises a plurality of high-index zones having a high refractive index (n2) and a plurality of low index zones having a low refractive index (n1), which are formed in the thickness of the flat glass between a first free surface and a second free surface, over a depth of between 1 and 1000 μm starting from the first free surface, said high-index zones and low-index zones alternating along a direction transverse to the thickness direction of the flat glass between the first free surface and second free surface, the high-index zones flaring out from the first free surface toward the second free surface, and the envelope surfaces of the high-index zones making an angle (θ) of at least 65°, with respect to the first free surface.