Narrow Results

Oblique light propagation through a chiral photonic crystal (PC) layer with gradient parameters of modulation is considered. The problem is solved by Ambartsumian's layer addition modified method. It is shown that suppressing of diffraction oscillations near the photonic band gap (PBG) is possible at certain conditions. Thus, at certain conditions, the spectra for the finite PC layer is the same as that for the half space.

We propose a reflective acoustic metasurface by taking advantage of the synergetic coupling of two kinds of widely used elements, the resonant cavity and the labyrinthine beam. A full 2$\pi$ phase shift range can be obtained by varying the neck width. The structure manipulates the reflective waves on a very deep subwavelength scale with the thickness being only 1/50 of the wavelength, which eliminates the enormous obstacle in low frequency applications. The synergetic coupling of the resonant cavity and the inner labyrinthine beams provide a useful guide for the design of acoustic metasurfaces.

We report a graphene-based tunable ultra-narrowband mid-infrared filter which can be tuned from 4.45122 $\mu$m to 4.44675 $\mu$m by tuning the Fermi level from 0.2 eV to 0.6 eV. Furthermore, the reflection bandwidth is less than 0.2 nm and the reflection rate is more than 0.55. The ultra-narrowband filter is designed based on the guided-mode resonance (GMR) effect. The shift of reflection peak is mainly caused by the change of the real part of the graphene’s permittivity. This tunable ultra-narrowband mid-infrared filter can be applied in the mid-infrared microscopy.

In this paper, photovoltaics (PV)- or solar cells based on two types of nanoparticles have been investigated. The suggested four-layer solar cell model consists of metallic nanoparticle (Ag–Au) layers that are Si-based and covered by SiN. The transmission and reflection of the incident light on the structure model have been computed for different physical parameters of the structure. Higher transmission and lower reflections have been obtained leading to higher efficiency of the solar cells. The matrix model is used, and the numerical results obtained by MAPLE Software Program. The obtained results confirm that the nanoparticle solar cell structure can effectively enhance the efficiency of such structure model.

A complete and fully developed theory of all optical phenomena (refraction, reflection, absorption, and transparency) and the corresponding optical properties of ultrathin crystalline films (optical indices) are presented in this paper, especially along the direction in which the structure is spatially limited (perpendicular to surfaces). While these indices depend on the position of the crystallographic plane (where the mentioned optical phenomena occur) with respect to the two interfaces, these values can be measured/ determined in experiments only for the film as a whole. For these reasons, it is important to answer the question of how to define these optical indices precisely.

We study the propagation of nonlinear waves in a three-component reaction–diffusion system. The problem of the existence of the stationary pulse-like solutions is reduced to the analysis of homoclinic trajectories of a fourth-order system of nonlinear ODEs. We have obtained the parameter set corresponding to the homoclinic bifurcations that defines the velocity spectra of the traveling pulses. We have shown that the pulses behave like autowaves annihilating in head-on collision and like dissipative solitons crossing each other, reflecting at boundaries. We have provided a qualitative explanation for such a behavior.

The optical properties of the various types of tapered silicon nanowires (SiNWs) have been investigated by the phase retrieving method of utilizing the experimental reflection spectra with the aid of the Kramers–Kronig (KK) relation. The effective refractive index (n) and the extinction coefficient (K) of each tapered SiNWs and combined silicon nanowires and microwires (CNMW) array samples can be obtained from concrete simulation by the KK relation. At the same time, we can also obtain the real part (ε′) and imaginary part (ε″) of the effective complex dielectric constant from the relation between the refractive index and the complex dielectric constant of samples. And the simulated results show that the relative material parameters (effective complex refractive index, effective complex dielectric function) can be modulated from a concrete material processing.