Customization and analysis of structured singular light fields

Abstract

Within the last decades, laser light has advanced from the typical Gaussian beam to structured light fields, spatially varying in its amplitude, phase, and/or polarization beyond the Gaussian shape. In this case, continuously changing light field properties vary around its ‘skeleton’, formed by optical singularities—namely, points, lines, or surfaces in which specific properties of light are undefined. Although optical singularities even appear in natural sunlight, only recently all kinds of singularities, especially in polarization-structured light, have became experimentally accessible. This progress has decisively pushed research in this area, allowing for novel insights into the fundamental nature of singular light and establishing structured singular light as a key tool for advanced applications as high-dimensional quantum key distribution, to name only one. Though research has evolved rapidly from the study of scalar to vectorial, and paraxial to non-paraxial (tightly focused) structured fields, a concise overview on the implemented realizations and analysis approaches is still missing. In this tutorial, we introduce the fundamentals of structured light fields and optical singularities in the paraxial as well as non-paraxial regime, provide the tools for its analysis, and exemplify its customization by holographic approaches.