| 摘要 |
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.
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