Due to its ability to meet requirements such as e.g. telemetry, millimeter-wave transceiver technology has gained research interest for various sensor applications, including the automotive and consumer sector. This work presents a resonant metamaterial for millimeter-waves that enables telemetric position sensing. The concept is based on a resonant unit cell that can be tuned to enable position encoding. A 2D metamaterial design was developed to parametrize the resonance frequency via a geometric parameter of the structure. The tuneable range of the metamaterial was estimated using a finite element method (FEM) simulation. This allowed for a bijective mapping of resonance frequency and the geometric parameter, where a linear range for the sensor effect was selected. The resonance frequency shift encodes the absolute position via the geometry parameter of the metamaterial. A linear position encoded bar was fabricated using well-known PCB manufacturing techniques for position determination. The position encoded metamaterial was successfully tested with a vector network analyser under lab conditions. This telemetric position sensor concept offers a compact and contactless readout without mechanical interference with the moving object. The metamaterial is completely passive, resulting in low maintenance and failure issues. The overall sensor concept includes a state-of-the-art radar chip as millimeter-wave transceiver which is currently under development.
A distinguishing feature of high-index dielectric nanoparticles is their ability to support strong Mie resonances, thereby enhancing the interaction of light with matter and minimizing Ohmic losses, leading to unprecedented efficiency. An important advancement in this field is the investigation of the "transverse Kerker" effect, in which both forward and backward scattering are significantly reduced while lateral scattering is enhanced. We uncover that the realization of a perfect transverse Kerker effect is possible even in passive structures, by exploiting the physics of bound states in the continuum—electromagnetic states remaining localized in photonic structures, coexisting with outgoing waves. Such 'transverse Kerker BICs' are polarization independent, and in momentum space are pinned at the center of polarization vortices with high order topological charges.
The ability to precisely measure the displacement between two elements, e.g. a mask and a substrate or a beam and optical elements, is fundamental to many precision experiments and processes. Yet typical optical displacement sensors struggle to go significantly below the diffraction limit. Here we combine advances in our understanding of directional scattering from nanoparticles with silicon photonic waveguides to demonstrate a displacement sensor with deep subwavelength accuracy. Depending on the level of integration and waveguide geometry used we achieve a spatial resolution between 5 − 7 nm, equivalent to approximately λ/200 − λ/300.
Light is a vector field often displaying a complex structure. Parameters such as amplitude, phase and the polarization, i.e., the direction of the electric field vector may change drastically in space even over sub-wavelength dimensions, giving rise to exotic properties such as phase singularities, polarization vortices and exotic angular momenta. These properties of light can be measured by letting it interact with sub-wavelength particles and detecting the scattered light. In reverse, by illuminating a small particle with properly designed light one can steer the scattered light and sensitively measure the particle position. These and related effects will be reviewed.
A beam of light may exhibit a spatially varying polarization distribution. Furthermore, the polarization can also be locally singular or undefined, similar to the case of phase singularities found in scalar fields. In this context, Nye introduced a classification of such polarization singularities, which provides a very useful language for the study of polarized fields.
If electromagnetic fields get spatially confined, exotic polarization phenomena and topologies can be observed. For instance, Freund proposed the appearance of so-called optical polarization Möbius strips in tailored three-dimensional electromagnetic field distributions created by intersecting two differently shaped and polarized light beams. The existence of such exotic structures was recently also proven experimentally for tightly focused polarization tailored light beams.
In this presentation, we will briefly introduce our experimental scheme for measuring the electromagnetic field distribution of light at the nanoscale. Furthermore, we will review our recent and ongoing work on three-dimensional polarization topologies created by tight focusing of tailored or conventionally polarized light beams. We will also elaborate on the connection between points of transverse angular momentum and the existence of (Möbius-like) polarization structures in the propagation plane.
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