Near and far field

About: Near and far field is a research topic. Over the lifetime, 15922 publications have been published within this topic receiving 220571 citations.

Near-field scanning microwave microscope using dielectric resonator

Abstract: Provided is a near-field microscope using a dielectric resonator, which makes it possible to minimize influences by external environments, and to enhance its sensitivity, resolution and function by adjusting the distance between a sample and an apex of a probe. The near-field microscope includes a wave source, a dielectric resonator, a probe, a distance adjusting unit, and a detector. The wave source generates a wave, and a frequency of the wave is adjustable by the wave source. The dielectric resonator propagates the wave from the wave source, and a resonance frequency, impedance, a Q factor and an electromagnetic wave mode of the wave is freely adjustable. The probe scans the wave output from the dielectric resonator on a sample. The distance adjusting unit measures a distance between the probe and the sample and maintains the distance to a predetermined value. The detector detects a wave that propagates through the probe, interacts with the sample and then propagates through the probe and the dielectric resonator.

Numerical simulations of interference effects in photon-assisted electron energy-loss spectroscopy

Abstract: Although the electromagnetic resonances of individual nanostructures can be studied by electron or photon interactions alone, exciting new possibilities open up through the simultaneous use of both. In photon-induced near-field electron microscopy (PINEM), for example, single nanostructures are optically excited by short, intense pulses and concurrently imaged with high spatial resolution by fast electrons, which act as negligible probes of electric fields. Controlling their relative arrival time provides access to the dynamics of the electromagnetic response in the near field by recording images of the electron energy loss (or gain) spectra. In this paper, we investigate the transition from optically dominated PINEM to conventional, electron-dominated electron energy-loss spectroscopy (EELS). During the systematic reduction of optical excitation intensity to zero, a novel electro-optical interference effect emerges. It reveals itself at those optical field strengths that lead to prominently visible constructive and destructive interference patterns of the optical and electron radiation fields which are scattered by a nanostructure. The interference patterns reported here allow one to achieve higher temporal, energy and spatial resolutions of the modal dynamics in electron microscopy.

Polarization singularities on high index nanoparticles

Abstract: In this article, we study the emergence of polarization singularities in the scattered fields of optical resonators excited by linearly polarized plane waves. First, we prove analytically that combinations of isotropic electric and magnetic dipoles can sustain L surfaces, and C lines that propagate from the near-field to the far field. Moreover, based on these analytical results, we derive anomalous scattering Kerker conditions trough singular optics arguments. Secondly, through exact full-field calculations, we demonstrate that high refractive index spherical resonators present such topologically protected features. Furthermore, we calculate the polarization structure of light around the generated C lines, unveiling a Mobius strip structure in the main axis of the polarization ellipse. These results prove that high-index nanoparticles are excellent candidates for the generation and control of polarization singularities and that they may lead to new platforms for the experimental study of the topology of light fields around optical antennas.