Dynamical tuning between nearly perfect reflection, absorption, and transmission of light via graphene/dielectric structures

Nearly Perfect Transmission of Lamé Modes in a Rectangular Beam with Part and Through-Thickness Vertical Cracks

The guided waves in the uniform waveguide of rectangular cross-section exhibit complicated propagation and scattering characteristics due to the diversity of vibration modes. This paper focuses on the mode conversion of the lowest Lamé mode at a part-through or through-thickness crack. Firstly, the Floquet periodicity boundary condition is applied to derive the dispersion curves in the rectangular beam, which relates the axial wavenumber to the frequency. On this basis, the frequency domain analysis is conducted to investigate the interaction between the fundamental longitudinal mode in the vicinity of the first Lamé frequency and a part-through or through-thickness vertical or inclined crack. Finally, the nearly perfect transmission frequency is evaluated by extracting displacement and stress harmonic fields throughout the cross-section. It is shown that this frequency originates from the first Lamé frequency, increases with the crack depth, and decreases with the crack width. Between them, the crack depth plays a major role in the frequency variation. In addition, the nearly perfect transmission frequency is negligibly affected by the beam thickness, and such a phenomenon is not observed for inclined cracks. The nearly perfect transmission may have potential applications in the quantitative evaluation of crack size.

Graphene coated dielectric resonator antenna for modeling the photoreceptors at visible spectrum

The absorption of light is very important task for retina photoreceptors. Graphene is an energy harvesting material and one of the best models for the electromagnetic wave absorption and its conversion into signals. In this paper, an electromagnetic modeling of human retinal photoreceptors has been presented based on graphene coated material as a receiver antenna. The proposed electromagnetic model based on dielectric resonator antenna (DRA) is being analyzed for retina photoreceptors of human eye (cones and rods) by Finite Integral Method (FIM) collaborated with CST MWS. The results show that the model is good for vision spectrum with a proper field enhancement in cone photoreceptor due to its sensitivity to light. The results indicate proper S₁₁ (return loss below −10 dB) with invaluable resonances in a wide range of frequencies from 405 THz to 790 THz (vision spectrum), suitable S₂₁ (insertion loss 3-dB bandwidth), very good field distribution for flowing the power within desired radiation characteristics. The drawbacks of conventional model (no coating) have been resolved by presenting this one at blue spectrum specifically. Finally, mfERG clinical and experimental results show that this model can stimulate the electrochemical voltages and currents in photoreceptor cells.