Abstract: The invention concerns a two-dimensional diffraction gratting for the dispersion of polychromatic or quasi-monochromatic luminous flux including a substrate (2) having a surface (3), a first (5) and a second (6) stacks of thin biperiodic layers of period d in the thickness direction, including at least ten periods, each period d being formed of layers of at least two different materials (7, 8), said stacks (5, 6) forming contiguous lines (11) of width p/2, parallel to one another, and repeated periodically along a direction parallel to the surface of the substrate (2) with a period p, the second stack (6) being alternate with the first stack (5) and offset in width by d/2, so that the stacks (5 and 6) form a thick gratting (9) carried by the substrate (2). According to the invention, said thick grafting (9) consists of the doubly periodical repetition of a same unit cell, topped with a thin surface gratting (10) having an amplitude at the most equal to d/2.