FPGA-Implemented Fractal Decoder with Forward Error Correction in Short-Reach Optical Interconnects

Forward error correction (FEC) codes combined with high-order modulator formats, i.e., coded modulation (CM), are essential in optical communication networks to achieve highly efficient and reliable communication. The task of providing additional error control in the design of CM systems with high-performance requirements remains urgent. As an additional control of CM systems, we propose to use indivisible error detection codes based on a positional number system. In this work, we evaluated the indivisible code using the average probability method (APM) for the binary symmetric channel (BSC), which has the simplicity, versatility and reliability of the estimate, which is close to reality. The APM allows for evaluation and compares indivisible codes according to parameters of correct transmission, and detectable and undetectable errors. Indivisible codes allow for the end-to-end (E2E) control of the transmission and processing of information in digital systems and design devices with a regular structure and high speed. This study researched a fractal decoder device for additional error control, implemented in field-programmable gate array (FPGA) software with FEC for short-reach optical interconnects with multilevel pulse amplitude (PAM-M) modulated with Gray code mapping. Indivisible codes with natural redundancy require far fewer hardware costs to develop and implement encoding and decoding devices with a sufficiently high error detection efficiency. We achieved a reduction in hardware costs for a fractal decoder by using the fractal property of the indivisible code from 10% to 30% for different n while receiving the reciprocal of the golden ratio.     

Obtaining ZnO/CIS heterostructures

ZnO/CuInSe₂ heterostructures were obtained by sequential evaporation of elements. Firstly, a layer of Zn was deposited on the glass substrate by the magnetron sputtering method in vacuum. Needle-shaped nanostructures of ZnO were grown from the prepared Zn films by thermal annealing in the air. Secondly, Se, In and Cu layers were sequentially deposited onto these structures. The obtained samples were then annealed at 400 °C to form the CuInSe₂ (CIS) compound. The morphology, composition and phase identification were obtained using the scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis methods.     

Genotoxic Evaluation of Fe3O4 Nanoparticles in Different Three Barley (Hordeum vulgare L.) Genotypes to Explore the Stress-Resistant Molecules

Sustainable agricultural practices are still essential due to soil degradation and crop losses. Recently, the relationship between plants and nanoparticles (NPs) attracted scientists’ attention, especially for applications in agricultural production as nanonutrition. Therefore, the present research was carried out to investigate the effect of Fe₃O₄ NPs at low concentrations (0, 1, 10, and 20 mg/L) on three genotypes of barley (Hordeum vulgare L.) seedlings grown in hydroponic conditions. Significant increases in seedling growth, enhanced chlorophyll quality and quantity, and two miRNA expression levels were observed. Additionally, increased genotoxicity was observed in seedlings grown with NPs. Generally, Fe₃O₄ NPs at low concentrations could be successfully used as nanonutrition for increasing barley photosynthetic efficiency with consequently enhanced yield. These results are important for a better understanding of the potential impact of Fe₃O₄ NPs at low concentrations in agricultural crops and the potential of these NPs as nanonutrition for barley growth and yield enhancement. Future studies are needed to investigate the effect of these NPs on the expression of resistance-related genes and chlorophyll synthesis-related gene expression in treated barley seedlings.     

Investigations of As-S-Se thin films for use as inorganic photoresist for digital image-matrix holography

As-S-Se chalcogenide thin films are successfully employed in classical and dot-matrix holography as inorganic photoresists for obtaining a relief-phase hologram. However using these films for image-matrix hologram recording has not been studied due to some features of image-matrix technology. For the applied research of the optical properties of As-S-Se films an experimental device of digital image-matrix holographic recording based on 100 mW 405 nm semi-conductor laser and Spatial Light Modulator (SLM) has been created. The device has the following main parameters: 140 × 105 μm frame size; laser intensity during exposure 10 W/cm². With the help of this device diffraction grating and security holograms were recorded on As-S-Se thin films. The work reported herein presents results of an experimental study of how diffraction efficiency (DE) of the received relief-phase holographic gratings depends on an exposure and period. Diffraction grating profiles and speed of etching corresponding to different exposure doses are shown. Hologram samples with DE = 65% have been received which allows for using chalcogenide film as alternative to organic photoresists in applied dot-matrix and image-matrix holography.     

Second harmonic generation in selenium-metal structures

Results of second harmonic (SH) generation in amorphous and crystalline selenium films and selenium-metal (Ga, Zn, In, Sb, Bi) sandwich structures induced by titan-sapphire femtosecond laser (wavelength λ – 690–1040 nm) are presented. It is found that the highest intensity of SH is provided by fundamental wave at wavelength 1000 nm and it reaches maximum in approximately 100 s. The intensity of transmitted SH depends on film thickness while that of reflected does not. The highest SH intensities in selenium-metal structures are provided by Se–Ga and Se–Zn films. A possible mechanism for central symmetry breaking in amorphous films also is proposed.     

Electron beam induced surface modification of amorphous Sb2Se3 thin film

The change in the surface morphology of amorphous Sb₂Se₃ thin films during the electron beam irradiation has been studied mainly by atomic force microscopy (AFM). Electron beam at accelerating voltages 30 kV is focused onto the surface of the specimens of 100-μm thickness, and then the surface morphology of each specimen has been observed by AFM in air. The modification of the film surface includes lateral and vertical resizing which is typically in the micrometer and sub-micrometer range. Protrusions above the surface as high as 90 nm are observed at 180 pA electron beam current, whilst trenches as deep as 97 nm are observed at 800 pA electron beam current (total thickness of thin film is 100 nm). The dependence of patterns characteristics on irradiation parameters such as exposure time and beam current has also been studied. Physical mechanisms for trench and mound formation are proposed.     

On the Existence of Pure,Broadband Toroidal Sources in Electrodynamics

Multipoles are paramount for describing electromagnetic fields in many areas of nanoscale optics, playing an essential role in the design of devices in plasmonics and all-dielectric nanophotonics. Challenging the traditional division into electric and magnetic moments, toroidal moments are proposed as a physically distinct family of multipoles with significant contributions to the properties of matter. However, the apparent impossibility of separately measuring their response sheds doubt on their true physical significance. Here, the possibility of selectively exciting toroidal moments is confirmed without any other multipole. A set of general conditions is developed that any current distribution must fulfill to be entirely described by toroidal moments and prove the results in an analytically solvable case. The new theory allows to design and verify experimentally an artificial structure supporting a pure broadband toroidal dipole response in the complete absence of the electric dipole and other “ordinary” multipole contributions. In addition, a structure capable of supporting a novel type of non-radiating source is proposed- a “toroidal anapole,” originating from the destructive interference of the toroidal dipole with the unconventional electromagnetic sources known as mean square radii. The results in this work provide conclusive evidence on the independent excitation of toroidal moments in electrodynamics.     

Nanostructure formation on metal-chalcogenide surface using electron beam irradiation

In this letter, we demonstrate a method to form a nano-structured pattern on metal-chalcogenide sandwich like structures, using electron beam (EB) irradiation. After pointing EB at surface, we observed nano-dots and nano-lines formation on metal-chalcogenide (AgS, AgSe, CuS, CuSe) surface, considerably made of Ag or Cu, depending on metal in compound (Ag or Cu). This technique is based on the solid-state electrochemical reaction between EB and surface. Our results demonstrate repeatable metal structures with dimension of nanometers. As this process is carried out with scanning electron microscope (SEM) and does not require wet chemicals, it has potential for use as a simple metal patterning technique to fabricate functional structures and devices.