All-optical logic gates using a plasmonic MIM waveguide and elliptical ring resonator

All - optical logic gates OR, XOR, AND and NOT based on two - dimensional ( 2D ) plasmonic metal - insulator - metal ( MIM ) coupled with Elliptical Ring Resonator ( ERR ) are presented , simulated and investigated by using the numerical method of the FEM (finite elements method ). The results are compared and validated with the finite difference time domain ( FDTD ) method . The proposed logic gates are achieved with the same structure using the constructive and destructive optical interferences between a control signal and input signal(s). Their characterization was mainly done for two spectral regions , visible and near - infrared . A high intensity contrast ratios (CR) between the logic states ( “1” and “0” ) can be achieved (28 dB ) at these spectral regions . We introduce a new parameter , "gap- threshold ratio ( GTR )", to characterize the gap between the maximum and minimum of the transmitted signal intensity for all logic gates. The suggested value of transmission threshold between logic 0 and logic 1 states is T th =0.2 . A comparison of the two parameters , (CR) and ( GTR ), with previous works shows that the proposed structure gives very good results for all logic gates configurations. The proposed all- optical logic gates configuration can be a key components in optical processing and telecommunication devices .

Design of Wideband Elliptical Ring Monopole Antenna Using Characteristic Mode Analysis

This paper presents the systematic design of an elliptical ring monopole wideband antenna using characteristic mode analysis. The modal analysis is used to analyze the bandwidth and the radiation performance of the radiating patch. The resonance frequencies of three characteristic modes are close to each other with similar modal current distributions and characteristic fields. These three characteristic modes are simultaneously excited by an effective feeding technique. The proposed model achieves wideband characteristics. The proposed model is printed on an inexpensive FR4 substrate with a size of 20 mm × 18 mm × 1.6 mm and has a wide impedance bandwidth of 124.4% in the range of 3.6–15.46 GHz. The prototype has been fabricated and the measured results show good agreement with simulated results. The antenna will cover WLAN, WiMAX, Wi-Fi, and X-band applications.

Experimental and Numerical Investigations of Backscatter Patterns of the Blocks of Masking Digital Two-Bit Meta-covers

Introduction. The scattering patterns of non-absorbing coded checkerboard-like meta-coatings (MCs) applied for reducing the radar cross section (RCS) of metal surfaces inevitably contain side diffraction lobes. Therefore, the development of MCs with a low level of diffraction lobes is relevant. For this purpose, it is proposed to use checkerboard-like MCs in the form of a set of several basic flat blocks with the same dimensions. The paper discusses two such basic MC blocks with different coding matrices. The cells of the metasurface contain two coupled elliptical ring resonators and are distinguished by a 2-bit coding of the tilt angle of the anisotropy axis. Coding matrices of the MC blocks are built according to the block principle.Aim. To investigate experimentally and numerically backscatter patterns (BSP) for consonant (co-) and orthogonal (cross-) polarizations of the two developed flat blocks of the 2-bit digital nonabsorbing anisotropic MCs for different planes and polarizations of irradiation.Materials and methods. Full-wave simulation of the MC blocks was carried out using the HFSS software by the finite element method. BSP measurements of the fabricated MC layouts were performed in an anechoic chamber of the Center for Collective Usage “Applied Electrodynamics and Antenna Measurements” of the Southern Federal University using an automated information and computing complex.Results. The RCS reduction for the two blocks under normal irradiation is approximately the same and not less than 12 dB over the 9.8…21 GHz band. A good matching between the simulation and measurement results of backscattering patterns of the blocks in the region of the central lobes for various planes and polarizations of the irradiation is noted. In the principal planes, the blocks cancel the central lobes of the BSP by 10…25 dB; in the sector of angles of around ±40°, the backward RCS of the blocks is lower than that of the reference. In the diagonal planes, there is a cancellation of the RCS by 13…15 dB and an expansion of the central lobe of the BSP for copolarizations, as well as a bifurcation of this lobe for crosspolarizations in the sector of angles ±9°; outside of this sector the RCSs of the blocks are commensurate with the RCS of the reference.Conclusion. The developed blocks of the 2-bit digital nonabsorbing anisotropic MCs can be used for broadband cancellation of the RCS of metal surfaces.

Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum

We present a cryo-EM structure of the light-harvesting-reaction center (LH1-RC) core complex from purple phototrophic bacterium Rhodospirillum (Rsp.) rubrum at 2.76 Å resolution. The LH1 complex forms a closed, slightly elliptical ring structure with 16 αβ-polypeptides surrounding the RC. Our biochemical analysis detected rhodoquinone (RQ) molecules in the purified LH1-RC, and the cryo-EM density map specifically positions RQ at the QA site in the RC. The geranylgeraniol sidechains of bacteriochlorophyll (BChl) aG coordinated by LH1 β-polypeptides exhibit a highly homologous tail-up conformation that allows for interactions with the bacteriochlorin rings of nearby LH1 α-associated BChls aG. The structure also revealed key protein–protein interactions in both N- and C-terminal regions of the LH1 αβ-polypeptides, mainly within a face-to-face structural subunit. Our findings enable to evaluate past experimental and computational results obtained with this widely used organism and provide crucial information for more detailed exploration of light-energy conversion, quinone transport, and structure—function relationships in pigment-protein complexes.

Constraints on Newtonian Interplanetary Point-Mass Interactions in Multicomponent Systems from the Symmetry of Their Cycles

Interplanetary interactions are the largest forces in our Solar System that disturb the planets from their elliptical orbits around the Sun, yet are weak (<10−3 Solar). Currently, these perturbations are computed in pairs using Hill’s model for steady-state, central forces between one circular and one elliptical ring of mass. However, forces between rings are not central. To represent interplanetary interactions, which are transient, time-dependent, and cyclical, we build upon Newton’s model of interacting point-mass pairs, focusing on circular orbits of the eight largest bodies. To probe general and evolutionary behavior, we present analytical and numerical models of the interplanetary forces and torques generated during the planetary interaction cycles. From symmetry, over a planetary interaction cycle, radial forces dominate while tangential forces average to zero. Our calculations show that orbital perturbations require millennia to quantify, but observations are only over ~165 years. Furthermore, these observations are compromised because they are predominantly made from Earth, whose geocenter occupies a complex, non-Keplerian orbit. Eccentricity and inclination data are reliable and suggest that interplanetary interactions have drawn orbital planes together while elongating the orbits of the two smallest planets. This finding is consistent with conservation principles governing the eight planets, which formed as a system and evolve as a system.

None sharp corner localized surface plasmons resonance based ultrathin metasurface single layer quarter wave plate

We report on a non-sharp-corner quarter wave plate (NCQW) within the single layer of only 8 nm thickness structured by the Ag hollow elliptical ring array, where the strong localized surface plasmons (LSP) resonances are excited. By manipulating the parameters of the hollow elliptical ring, the transmitted amplitude and phase of the two orthogonal components are well controlled. The phase difference of π/2 and amplitude ratio of 1 is realized simultaneously at the wavelength of 834 nm with the transmission of 0.46. The proposed NCQW also works well in an ultrawide wavelength band of 110 nm, which suggests an efficient way of exciting LSP resonances and designing wave plates, and provides a great potential for advanced nanophotonic devices and integrated photonic systems.