Hybrid curved nano-structured micro-optical elements.

Tailoring the spatial degree of freedom of light is an essential step towards the realization of advanced optical manipulation tools. A topical challenge consists of device miniaturization for improved performance and enhanced functionality at the micron scale. We demonstrate a novel approach that combines the additive three-dimensional (3D) structuring capability of laser polymerization and the subtractive subwavelength resolution patterning of focused ion beam lithography. As a case in point hybrid (dielectric/metallic) micro-optical elements that deliver a well-defined topological shaping of light are produced. Here we report on hybrid 3D binary spiral zone plates with unit and double topological charge. Their optical performances are compared to corresponding 2D counterparts both numerically and experimentally. Cooperative refractive capabilities without compromising topological beam shaping are shown. Realization of advanced designs where the dielectric architecture itself is endowed with singular properties is also discussed.