PARTIALLY ETCHED PHASE-TRANSFORMING OPTICAL ELEMENT

摘要

An optical element includes a substrate, an intermediate layer, a topmost layer, and a contiguous multitude of recessed and non-recessed areal regions. The intermediate layer is formed over a top surface of the substrate and has a refractive index n_I. The topmost layer is formed directly on the intermediate layer and has a refractive index n_T where n_T≠n_I. The intermediate and topmost layers are substantially transparent over an operational wavelength range that includes a design wavelength λ₀. A subset of areal regions has a largest transverse dimension less than about λ₀. Each non-recessed areal region includes corresponding portions of the intermediate and topmost layers. Each recessed areal region extends entirely through the topmost layer and at least partly through the intermediate layer. A fill medium fills the recessed areal regions. The areal regions are variously sized and distributed transversely across the optical element.