Strong near-field couplings of anapole modes and the formation of higher-order electromagnetic modes in stacked all-dielectric nanodisks

We theoretically study the near-field couplings of two stacked all-dielectric nanodisks, where each disk has an electric anapole mode consisting of an electric dipole mode and an electric toroidal dipole (ETD) mode. Strong bonding and anti-bonding hybridizations of the ETD modes of the two disks can occur. The bonding-hybridized ETD can interfere with the dimer's electric dipole mode and induce a new electric anapole mode. The anti-bonding hybridization of the ETD modes can induce a magnetic toroidal dipole (MTD) response in the disk dimer. The MTD and magnetic dipole resonances of the dimer form a magnetic anapole mode. Thus, two dips associated with the hybridized modes appear on the scattering spectrum of the dimer. Furthermore, the MTD mode is also accompanied by an electric toroidal quadrupole mode. The hybridizations of the ETD and the induced higher-order modes can be adjusted by varying the geometries of the disks. The strong anapole mode couplings and the corresponding rich higher-order mode responses in simple all-dielectric nanostructures can provide new opportunities for nanoscale optical manipulations.

Origin of the hemispheric asymmetry of solar activity

The frequency spectrum of the hemispheric asymmetry of solar activity shows enhanced power for the period ranges around 8.5 years and between 30 and 50 years. This can be understood as the sum and beat periods of the superposition of two dynamo modes: a dipolar mode with a (magnetic) period of about 22 years and a quadrupolar mode with a period between 13 and 15 years. An updated Babcock–Leighton-type dynamo model with weak driving as indicated by stellar observations shows an excited dipole mode and a damped quadrupole mode in the correct range of periods. Random excitation of the quadrupole by stochastic fluctuations of the source term for the poloidal field leads to a time evolution of activity and asymmetry that is consistent with the observational results.

Detection of Sectoral Modes in the Eclipsing Binary KIC 4851217

KIC 4851217 is a short period eclipsing binary (P = 2.47 days) in the field of the Kepler K1 mission. As well as variability caused by the eclipses, low-amplitude pulsations are also present in the data. A frequency analysis of the residual light-curve revealed δ Sct pulsations in the frequency range from 15–21 d−1 with amplitudes up to 3.5 mmag. Strong linear coupling (fi = fp + kforb) to orbital frequency was found, indicating tidally locked modes. From an analysis of 5 selected groups of frequencies we identified a radial mode on the secondary component, 3 dipole modes (l = |m| = 1), one of them present on the secondary component, and a quadrupole mode (l = |m| = 2), also located on the secondary component.

Numerical Study of Plasmon Resonance Silver Nanoparticles Coated Polyvinyl Alcohol (PVA) using Bohren-Huffman-Mie Approximation

<p class="TTPAbstract">In this study, we have investigated the LSPR spectra of the silver nanoparticles (Ag-NPs) coated by polyvinyl alcohol (PVA) by means of a numerical study using Bohren-Huffman-Mie (BHMie) approximation. The LSPR of Ag-NPs shifted to red-shift as the diameter size of Ag-NPs and the thickness of PVA increased. The peak of the LSPR spectra exponentially increased as the thickness increased. Interestingly, there have three characteristic of the LSPR spectra, small, intermediate, and large diameter. In small diameter, the dipole resonant mode contributed to the LSPR spectra while in large diameter, the LSPR spectra originated from the quadrupole resonant mode. In contrast to intermediate diameter, the LSPR spectra originated from the competition between the dipole and the quadrupole mode. For this reason, at small and large diameter the LSPR peak has one peak and increased then until a certain thickness showed constant. Different at intermediate diameter, the LSPR peak appeared more one peak with major peak increased then until a certain thickness trend to decrease and minor peak followed at small diameter behavior.</p>

Numerical Study of Plasmon Resonance Silver Nanoparticles Coated Polyvinyl Alcohol (PVA) using Bohren-Huffman-Mie Approximation

<p class="TTPAbstract">In this study, we have investigated the LSPR spectra of the silver nanoparticles (Ag-NPs) coated by polyvinyl alcohol (PVA) by means of a numerical study using Bohren-Huffman-Mie (BHMie) approximation. The LSPR of Ag-NPs shifted to red-shift as the diameter size of Ag-NPs and the thickness of PVA increased. The peak of the LSPR spectra exponentially increased as the thickness increased. Interestingly, there have three characteristic of the LSPR spectra, small, intermediate, and large diameter. In small diameter, the dipole resonant mode contributed to the LSPR spectra while in large diameter, the LSPR spectra originated from the quadrupole resonant mode. In contrast to intermediate diameter, the LSPR spectra originated from the competition between the dipole and the quadrupole mode. For this reason, at small and large diameter the LSPR peak has one peak and increased then until a certain thickness showed constant. Different at intermediate diameter, the LSPR peak appeared more one peak with major peak increased then until a certain thickness trend to decrease and minor peak followed at small diameter behavior.</p>