Abstract
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.
Highlights
Advanced optical manipulation of matter at the microscopic scale implies the development of optical elements enabling on-demand structuring of electromagnetic fields [1,2,3]
In addition to the aforementioned refractive modifications, the proposed hybrid polymerisation and focused ion beam (FIB) milling design is useful for applications in microscopy and microfluidics where only an optical vortex beam should be generated with blocked light which does not pass through the binary transmission mask
We have reported on the realization and analysis of hybrid 3D micro-optical elements enabling optical phase engineering by combining 3D dielectric structures obtained from laser polymerization to subwavelength-thick metallic film patterned by focus ion beam milling
Summary
Advanced optical manipulation of matter at the microscopic scale implies the development of optical elements enabling on-demand structuring of electromagnetic fields [1,2,3]. Photoresist reflow method is employed to create micro-lenses with a subsequent laser writing step used to inscribe a di↵ractive phase correction element [4] Such hybridization is pursued either to circumvent limitations in fabrication method, as in the aforementioned example, or when additional flexibility is required for specific fields. The fact that the orbital degree of freedom has an unbound set of eigenstates formally has demonstrated great promise in optical communications [12, 13] This provides with enhanced optomechanical capabilities since a vortex beam with topological chargecarries~ angular momentum per photon [14] whereas the spin contribution is limited to ±~ angular momentum per photon. We propose to combine the additive 3D structuring capability of laser photopolymerization and the subtractive subwavelength resolution patterning of focused ion beam lithography to produce hybrid (dielectric/metallic) micro-optical elements for the purpose of topological shaping of light. Our results suggest that additive manufacturing methods such as 3D direct laser writing, once combined with state-of-the-art nanofabrication technologies, pave the way towards the realization of 3D hybrid metasurfaces of arbitrary complexity
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