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|1. (WO2018220271) METHOD OF MANUFACTURING A HEIGHT-MODULATED OPTICAL DIFFRACTIVE GRATING|
|Title:||METHOD OF MANUFACTURING A HEIGHT-MODULATED OPTICAL DIFFRACTIVE GRATING|
The invention concerns a method of manufacturing a height-modulated optically diffractive grating. The method comprises providing a substrate and manufacturing a plurality of temporary elements of first material onto the substrate, the elements being separated by gaps and arranged as a periodic structure comprising at least two periods having different element heights. A coating layer of second material is deposited on the plurality of temporary elements such that the coating layer fills said gaps and covers said temporary elements. Then, a uniform layer of the second material is removed in order to expose said temporary elements and the first material is removed in order to form a height -modulated pattern of the second material onto the substrate as the optically diffractive grating. The invention relaxes manufacturing constraints when manufacturing gratings with locally varying diffraction efficiency.