Enhancing Spectral Reflection through Controlled Phase Distribution Using Doped Polar-Dielectric Metasurfaces

Controlling the phase distribution of wavefronts using optical metasurfaces has led to interesting optical properties and applications. Here, we explore the control of phase distribution through polar-dielectric metasurfaces composed of doped SiC nanosphere arrays. We investigate the impact of doping concentration on the optical properties of SiC nano-spheres. Our results indicate that increasing the doping of SiC nanoparticles influenced electric dipolar resonances, whereas it did not change the dipolar resonances. Using this concept, we numerically studied the extension of this idea to form metasurface arrays of single, dimer and linear trimers of the doped SiC nano-spheres. Using different doping schemes, we studied the improvement of the reflectivity at frequencies greater than the longitudinal optical phonon frequency.

Быстрые приповерхностные изменения дефектной структуры в кристаллах тетрабората лития во внешнем электрическом поле

The results of study of the defect structure variation process in the near-surface layers of lithium tetraborate (Li2B4O7) single crystals under the influence of an external electric field applied along the [001] polar direction are presented. Using the X-ray diffractometry with 2 ms time resolution the dynamics of the 004 and 008 diffraction peak parameters (angular position and integral intensity) variation was determined. Two types of processes caused by redistribution of the charge localized at the surface of the polar dielectric and the migration of lithium ions were revealed with different velocity and response time to the external field switching. The measurements were carried out at voltages providing a reversible character of induced effects. The use of two orders of diffraction with different X-ray extinction length made it possible to visualize space charge layers near the anode and cathode by the intensity variation of the diffraction peaks. Estimation of the effective thickness of the charged surface layer gives a value of 25 μm for lithium ions at the cathode and about 45 μm for lithium vacancies at the anode.

Effect of Dielectric Imperfections on the Electroactive Deformations of Polar Dielectric Elastomers

We find that the ratio of dielectric permittivity to shear modulus is linearly related to the number of polar groups per polymer chain in polar dielectric elastomers (PDEs). Our discovery is verified via computational modeling and validated by experimental evidences. Based on the finding, we introduce the new concept of dielectric imperfection (DI) and provide some physical insights into understanding it through demonstrating the large nonlinear deformation of PDEs with DIs under electric fields. The results show remarkable DI-induced inhomogeneous deformation and indicate that the size and dielectric permittivity of DIs have a significant impact on the deformation stability of PDEs under electric fields. With this concept, we propose some potential applications of PDEs with DIs.