Reflective liquid crystal hybrid beam-steerer

We report on efficient optical beam-steering using a hot-embossed reflective blazed grating in combination with liquid crystal. A numerical simulation of the electrical switching characteristics of the liquid crystal is performed and the results are used in an FDTD optical simulator to analyze the beam deflection. The corresponding experiment on the realized device is performed and is found to be in good agreement. Beam deflection angles of 4.4° upon perpendicular incidence are found with low applied voltages of 3.4V. By tilting the device with respect to the incoming optical beam it can be electronically switched such that the beam undergoes either total internal reflection or reflection with a tunable angle

Tartaric Acid Synthetic Derivatives for Multi-Drug Resistant Phytopathogen Pseudomonas and Xanthomonas Combating

The resistance to antimicrobial preparations, according the WHO reports of recent years, is becoming the one of the most actual healthcare problems of this century. Nevertheless, the key role of antibiotics diversity increase, as well as the increase of their application scopes, the initial origin of antimicrobial resistance problem is the versatility of adaptation mechanisms potential of all microorganisms, including intraspecific gene horizontal transfer and quorum sensing. Thus, the actuality of search of new, ecologically safe and harmless for human health antimicrobial agents, among the natural and semisynthetic compounds, is being significantly increased. One of the prospective directions in these research is the derivatization of aldaric acids, isolated from plants different species, as the native antibacterial active substances, such as like: citric, acetic, tartaric, lactic.   In current research, 7 new derivatives of natural tartaric acid (TA): cyclohexylimide, benzylimide, phenylimide, benzyl mono amino salt, cyclohexyl mono amino salt, phenyl amino salt and mono ethanol amino salt of TA were tested on different strains from 6 subtypes of 3 species of phytopathogenic multi-drug resistant Xanthomonas and Pseudomonas. During the research it was detected the significant antimicrobial effect of studied compounds against the range of phytopathogens which are resistant to antibiotics from different classes and generations (ciprofloxacin, chloramphenicol, ceftriaxone, azithromycin, etc.). It was detected the higher efficiency of cyclohexyl- derivatives in comparison with mono ethanol-, phenyl- and benzyl- derivatives

Active optical beam shaping based on liquid crystals and polymer micro-structures

Emerging applications requiring light beam manipulation, such as high-efficiency sunlight concentrators for solar cells, switchable micro-lens arrays for autostereoscopic displays, tunable lenses for augmented reality goggles, auto-focusing spectacles, and smart contact lenses, mostly depend on one or more active optical components with the desired and controllable beam modifying functionalities, preferably manufactured at relatively low cost. Recent progress in research on components based on the combination of liquid crystals (LCs) and various polymer micro-structures is reviewed in this paper. It is found that such components can address the demands appropriately and have the potential of paving the way for large-scale applications of active optical beam shaping components

Armenian Elections

This interdisciplinary issue of the Caucasus Analytical Digest looks at some of the most common pre-election violations before and during the parliamentary elections in Armenia 2017, civil society’s observation missions, and challenges related to the electoral system. Sociologist and anthropologist Milena Baghdasaryan analyzes the workings of patron-client networks and some of the most pervasive violations that took place prior to the elections; political analyst Armen Grigoryan examines the development of civil society’s observation missions in Armenia since 2010 and their results and effectiveness during the parliamentary elections of 2017; finally, lawyer Tigran Yegoryan discusses the activities of the electoral administration bodies, the impact of the law enforcement practice on changes in the electoral law and vice-versa, and some of the problems and risks which have become apparent in the electoral processes.ISSN:1867-932

Next Generation Optical Networks Based on Higher-Order Modulation Formats, Coherent Receivers and Electronic Distortion Equalization, Elektrotechnik und Informationstechnik:

ABSTRACT Worldwide, higher-order modulation formats are intensively investigated to further increase spectral efficiency for building next generation optical transport networks. Coherent receivers and digital electronic equalizers are hereby discussed as the key enablers for applying very high spectral efficient wavelength division multiplexed (WDM) signals in future optical core and metro networks. We review current research on application of higher-order modulation formats with coherent detection and electronic distortion equalization

Media 4: Numerical modeling of femtosecond laser inscribed IR gratings in photonic crystal fibers

Originally published in Optics Express on 26 January 2015 (oe-23-2-709

Media 1: Numerical modeling of femtosecond laser inscribed IR gratings in photonic crystal fibers

Originally published in Optics Express on 26 January 2015 (oe-23-2-709

Media 2: Numerical modeling of femtosecond laser inscribed IR gratings in photonic crystal fibers

Originally published in Optics Express on 26 January 2015 (oe-23-2-709

Anomalous transparency in photonic crystals and its application to point-by-point grating inscription in photonic crystal fibers

Abstract It is common belief that photonic crystals behave similarly to isotropic and transparent media only when their feature sizes are much smaller than the wavelength of light. Here, we counter that belief and we report on photonic crystals that are transparent for anomalously high normalized frequencies up to 0.9, where the crystal’s feature sizes are comparable with the free space wavelength. Using traditional photonic band theory, we demonstrate that the isofrequency curves can be circular in the region above the first stop band for triangular lattice photonic crystals. In addition, by simulating how efficiently a tightly focused Gaussian beam propagates through the photonic crystal slab, we judge on the photonic crystal’s transparency rather than on isotropy only. Using this approach, we identified a wide range of photonic crystal parameters that provide anomalous transparency. Our findings indicate the possibility to scale up the features of photonic crystals and to extend their operational wavelength range for applications including optical cloaking and graded index guiding. We applied our result in the domain of femtosecond laser micromachining, by demonstrating what we believe to be the first point-by-point grating inscribed in a multi-ring photonic crystal fiber