Najmeh Tabe Bordbar

Bio: Najmeh Tabe Bordbar is an academic researcher from University of the Witwatersrand. The author has contributed to research in topics: Polarization (waves) & Circular polarization. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

All-digital Stokes polarimetry with a digital micromirror device.

Abstract: Stokes polarimetry is widely used to extract the polarization structure of optical fields, typically from six measurements, although it can be extracted from only four. To measure the required intensities, most approaches are based on optical polarization components. In this work, we present an all-digital approach that enables a rapid measure of all four intensities without any moving components. Our method employs a polarization grating (PG) to simultaneously project the incoming mode into left- and right-circular polarized states, followed by a polarization-insensitive digital micromirror device (DMD), which digitally introduces a phase retardance for the acquisition of the remaining two polarization states. We demonstrate how this technique can be applied to measuring the SoP, vectorness, and intramodal phase of optical fields, without any moving components, and shows excellent agreement with theory, illustrating fast, real-time polarimetry.

Phase Singularities to Polarization Singularities

Abstract: Polarization singularities are superpositions of orbital angular momentum (OAM) states in orthogonal circular polarization basis. The intrinsic OAM of light beams arises due to the helical wavefronts of phase singularities. In phase singularities, circulating phase gradients and, in polarization singularities, circulating Stokes phase gradients are present. At the phase and polarization singularities, undefined quantities are the phase and Stokes phase, respectively. Conversion of circulating phase gradient into circulating Stokes phase gradient reveals the connection between phase (scalar) and polarization (vector) singularities. We demonstrate this by theoretically and experimentally generating polarization singularities using phase singularities. Furthermore, the relation between scalar fields and Stokes fields and the singularities in each of them is discussed. This paper is written as a tutorial-cum-review-type article keeping in mind the beginners and researchers in other areas, yet many of the concepts are given novel explanations by adopting different approaches from the available literature on this subject.

Vectorial light-matter interaction -- exploring spatially structured complex light fields

Abstract: Research on spatially-structured light has seen an explosion in activity over the past decades, powered by technological advances for generating such light, and driven by questions of fundamental science as well as engineering applications. In this review we highlight work on the interaction of vector light fields with atoms, and matter in general. This vibrant research area explores the full potential of light, with clear benefits for classical as well as quantum applications.

Classically entangled Ince-Gaussian modes

Abstract: Complex vector light modes, classically entangled in their spatial and polarization degrees of freedom (DoF), have become ubiquitous in a vast diversity of research fields. Crucially, while polarization is limited to a bi-dimensional space, the spatial mode is unbounded, and it can be specified by any of the sets of solutions the wave equation can support in different coordinate systems. Here, we report on a class of vector beams with elliptical symmetry where the spatial DoF is encoded in the Ince–Gaussian modes of the cylindrical elliptical coordinates. We outline their geometric representation on the higher-order Poincare sphere, demonstrate their experimental generation, and analyze the quality of the generated modes via Stokes polarimetry. We anticipate that such vector modes will be of great relevance in applications, such as optical manipulations, laser material processing, and optical communications among others.

Digital Stokes polarimetry and its application to structured light: tutorial.

Abstract: Stokes polarimetry is a mature topic in optics, most commonly performed to extract the polarization structure of optical fields for a range of diverse applications. For historical reasons, most Stokes polarimetry approaches are based on static optical polarization components that must be manually adjusted, prohibiting automated, real-time analysis of fast changing fields. Here we provide a tutorial on performing Stokes polarimetry in an all-digital approach, exploiting a modern optical toolkit based on liquid-crystal-on-silicon spatial light modulators and digital micromirror devices. We explain in a tutorial fashion how to implement two digital approaches, based on these two devices, for extracting Stokes parameters in a fast, cheap, and dynamic manner. After outlining the core concepts, we demonstrate their applicability to the modern topic of structured light, and highlight some common experimental issues. In particular, we illustrate how digital Stokes polarimetry can be used to measure key optical parameters such as the state of polarization, degree of vectorness, and intra-modal phase of complex light fields.