An optical element includes a surface including a tilted profile having height differences, thereby providing cavities and elevations having a predetermined maximum height difference, and a transmissive layer that covers the cavities and the elevations of the optical element. A first height of the transmissive layer in the cavities is substantially equal or larger than the predetermined maximum height difference and the transmissive layer has a second height on the elevations and the second height is about 10-500 nm. The transmissive layer is enabled to optically filter incident radiation, and the optical element is a grating.