Seeing the Unseen: Experimental Observation of Magnetic Anapole State Inside a High-Index Dielectric Particle

The existence of non-radiating electromagnetic sources attracts much attention in photonic community and gives rise to extensive discussions of various applications in lasing, medical imaging, sensing, and nonlinear optics. In this article, the existence of magnetic anapole states (or magnetic-type non-radiating sources) characterized by a suppressed magnetic dipole radiation in a dielectric cylindrical particle is theoretically predicted and experimentally demonstrated. The specific features of the magnetic anapole state under ideal conditions are identified, followed by a demonstration of how their existence can be detected in practical structures. The concept is valid in various frequency bands from visible range for nanoparticles to microwave range for millimeter size objects. The experimental study is performed in microwave frequency range which allows not only to measure the far-field (scattered field) characteristics, but also to probe the peculiar field profile directly inside the dielectric particle. The experimental results agree well with the analytical ones and pave the way to detect and identify nontrivial different-type anapole states.     

Specifics of hydrothermal synthesis of oriented zinc oxide nanorods on metallic zinc substrates

Zinc oxide nanostructures are prepared hydrothermally in the presence of ethylenediamine (EDA). The morphology and photoluminescent properties of final products are studied as functions of synthesis temperature, synthesis time, and EDA concentration. A decrease in EDA concentration to 30% favors the formation of more perfect and more ordered structures. Blank experiments show that hydrothermal synthesis without organic reagents does not produce nanostructures. When samples are sheltered from convective flows in the cell, the rod growth direction is dictated by the grain orientation in the foil. When nanorods are formed under low supersaturations (in the absence of convective flows), oxygen nonstoichiometry arises in the nanorods and appears in photoluminescence spectra as increased peak intensities in the green spectral range.     

Preparation,chemical features,structure and applications of membrane materials based on graphene oxide

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Sulfoethylated polyethylenimine: synthesis in gel and sorption properties

Using the gel synthesis approach of polymer-analogous transformations, N-sulfoethylation of polyethylenimine was carried out by treating the polymer with sodium vinyl sulfonate. The compositions and structures of the products were characterized by elemental analysis, FT-IR spectroscopy, and ¹H NMR spectroscopy. At pH 3.0–4.5 sulfoethylated polyethylenimine can selectively extract Ag^I and Cu^II from an ammonia—acetate buffer solution in the presence of a series of transition and alkaline-earth metals. At pH > 6.5 the sorbent can be used for the group extraction of a number of transition metal ions. The structural feature of the obtained derivative eliminates the selectivity of sorption of Ag^I ions compared to Cu^II ions, which has previously been revealed for the sulfoethylated derivatives of chitosan and polyaminostyrene.

     

3D Uniform Manipulation of NV Centers in Diamond Using a Dielectric Resonator Antenna

Ensembles of nitrogen-vacancy color centers in diamond hold promise for ultra-precise magnetometry, competing with superconducting quantum interference device detectors. By utilizing the advantages of dielectric materials, such as very low losses for electromagnetic field, with the potential for creating high Q-factor resonators with strong concentration of the field within it, we implemented a dielectric resonator antenna for coherent manipulation of a large ensemble of nitrogen-vacancy centers in diamond. We reached average Rabi frequency of 10 MHz in a volume of 7 mm³ with a standard deviation of less than 1% at a moderate pump power. The obtained result enables use of large volume low nitrogen-vacancy concentration diamond plates in modern nitrogen-vacancy magnetometers thus improving sensitivity via larger coherence time and higher optical detected magnetic resonance contrast.     

Microwave Spectroscopy of Ultracold Thulium Atoms

Magnetic fields are one of the main tools for controlling the interaction of ultracold atoms using the so-called Feshbach resonances. However, the accurate knowledge of magnetic fields within the high-vacuum chamber is significantly complicated due to the inexact knowledge of the setup geometry, the presence of magnetic parts, and other. In this paper, we demonstrate precision calibration of magnetic fields in the high-vacuum setup using microwave spectroscopy of the ground state of ultracold thulium atoms.     

Metamaterials with tunable nonlinearity

A new approach to the implementation of electromagnetic metamaterials with tunable nonlinearity in the microwave range has been proposed. The characteristics of a split ring resonator equipped with a varactor diode to ensure a nonlinear response and a photodiode to supply a dc bias voltage depending on the illumination intensity have been examined. It has been shown that an increase in the illumination intensity shifts the resonance response toward lower frequency and an increase in the power of the exciting signal shifts the resonance response toward higher frequency.