ON-CHIP NANOSCALE DIFFRACTIVE OPTICAL ELEMENT

A diffractive optical element (DOE) includes a substrate layer; and a nanostructure layer comprising nanostructures having a predetermined periodicity ranging from 0.75λ to 3λ of a target wavelength λ. The nanostructures are pillar-shaped nanostructures formed on a surface of the substrate layer, holes formed in the substrate layer, or a combination thereof. At least one nanostructure has a plan-view cross-sectional shape of a circle, an oval, a square, or a rectangle. The plan-view cross-sectional shape of at least one nanostructure includes a rounded corner having a corner radius selected based on a desired light dot nonuniformity of a diffraction pattern generated by the DOE. When the nanostructures are pillar-shaped, a refractive index of the nanostructures is greater than a refractive index of the substrate layer. When the nanostructures are holes, a refractive index of the nanostructures is less than a refractive index of the substrate layer.