Design, theory, and measurement of a polarization insensitive absorber for terahertz imaging

We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. We derive geometrical-independent conditions for effective medium absorbers in general, and for resonant metamaterials specically. Our fabricated design reaches and absorptivity of 78% at 1.145 ThzComment: 6 Pages, 5 figures; figures update

Comment on "Quantum Friction - Fact or Fiction?"

If quantum friction existed [J.B. Pendry, New J. Phys. 12, 033028 (2010)] an unlimited amount of useful energy could be extracted from the quantum vacuum and Lifshitz theory would fail. Both are unlikely to be true.Comment: Comment on J.B. Pendry, New J. Phys. 12, 033028 (2010

Symmetry and reciprocity constraints on diffraction by gratings of quasi-planar particles

Symmetry and reciprocity constraints on polarization state of the field diffracted by gratings of quasi-planar particles are considered. It is shown that the optical activity effects observed recently in arrays of quasi-planar plasmonic particles on a dielectric substrate are due to the reflection of the field at the air-dielectric slab interface and are proportional to this reflection coefficient.Comment: 11 pages, 3 figures, 12 references; minor corrections for better appearanc

Perfect lensing with phase conjugating surfaces: Towards practical realization

It is theoretically known that a pair of phase conjugating surfaces can function as a perfect lens, focusing propagating waves and enhancing evanescent waves. However, the known experimental approaches based on thin sheets of nonlinear materials cannot fully realize the required phase conjugation boundary condition. In this paper we show that the ideal phase conjugating surface is in principle physically realizable and investigate the necessary properties of nonlinear and nonreciprocal particles which can be used to build a perfect lens system. The physical principle of the lens operation is discussed in detail and directions of possible experimental realizations are outlined.Comment: 16 pages, 5 figure

Study (301)-(000) D2O band in 10200 - 10450 cm-1 spectral region

Measurements of D2O absorption spectra in the visible spectral region near 0.98 μm are performed using FT-spectrometer IFS-125M and Light-emitting diode (LED) as source of radiation. Water vapor spectrum has been obtained by averaging over 17136 scans recorded at 24 m optical path length, temperature 24 С and pressure of sample 27 mBar. Due to strong emission of LED source it was possible to achieve signal-to-noise ratio about 104 and to record weak lines with intensities of 6 10-27 cm/molecule. Comparisons with results of early works are made. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Repulsive Casimir Force in Chiral Metamaterials

We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.Comment: 4 pages, 4 figures, letter. submitted to Phys. Rev. Let

On homogenization of electromagnetic crystals formed by uniaxial resonant scatterers

Dispersion properties of electromagnetic crystals formed by small uniaxial resonant scatterers (magnetic or electric) are studied using the local field approach. The goal of the study is to determine the conditions under which the homogenization of such crystals can be made. Therefore the consideration is limited by the frequency region where the wavelength in the host medium is larger than the lattice periods. It is demonstrated that together with known restriction for the homogenization related with the large values of the material parameters there is an additional restriction related with their small absolute values. From the other hand, the homogenization becomes allowed in both cases of large and small material parameters for special directions of propagation. Two unusual effects inherent to the crystals under consideration are revealed: flat isofrequency contour which allows subwavelength imaging using canalization regime and birefringence of extraordinary modes which can be used for beam splitting.Comment: 16 pages, 12 figures, submitted to PR

Оптимизация параметров лазерного раскалывания силикатных стекол эллиптическими пучками в плоскости, параллельной поверхности

Regression and neural network models of the process of laser splitting of silicate glasses by elliptical beams in a plane parallel to the surface were obtained. To conduct a numerical experiment, a central compositional plan was used. The processing speed, laser beam power and its geometric parameters were selected as variable factors. As responses, the values of maximum temperatures and the values of maximum thermoelastic tensile stresses in the processing zone were determined, the calculation of which was performed using the APDL programming language. An effective architecture for an artificial neural network created using the TensorFlow program has been established. A comparative analysis of neural network and regression models was carried out. The influence of input parameters on responses was assessed. Using the MOGA algorithm of the ANSYS program, the optimal modes for the formation of laser-induced cracks by elliptical beams were determined, ensuring the effective implementation of parallel laser splitting of silicate glass.Получены регрессионные и нейросетевые модели процесса лазерного раскалывания силикатных стекол эллиптическими пучками в плоскости, параллельной поверхности. Для проведения численного эксперимента был использован центральный композиционный план. В качестве варьируемых факторов выбраны скорость обработки, мощность лазерного пучка и его геометрические параметры. В качестве откликов определялись значения максимальных температур и значения максимальных термоупругих напряжений растяжения в зоне обработки, расчет которых был выполнен с применением языка программирования APDL. Установлена эффективная архитектура искусственной нейронной сети, созданной с использованием программы TensorFlow. Проведен сравнительный анализ нейросетевых и регрессионных моделей. Выполнена оценка влияния входных параметров на отклики. С использованием алгоритма MOGA программы ANSYS определены оптимальные режимы формирования эллиптическими пучками лазерно-индуцированных трещин, обеспечивающие эффективную реализацию параллельного лазерного раскалывания силикатного стекла

Light-emitting-diode Fourier-transform spectroscopy of HD16O between 11200 and 12400 cm-1

The absorption spectrum of monodeuterated water, HDO has been investigated between 11200 and 12400 cm-1. The spectrum has been recorded using IFS-125M interferometer with spectral resolution of 0.05 cm-1. For measurements White’s-type cell were used. The bright light emitting diode (LED) EDEI-1LS3-R was applied as a source of radiation. Signal to noise ratio was about 104. The spectral line parameters - line positions, intensities and half-widths were obtained by least square fitting. As a result of the spectrum analysis the line list containing more than 1500 lines was created. The spectral line parameters have been compared with the previous measured and calculated data. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Finding co-solvers on Twitter, with a little help from Linked Data

In this paper we propose a method for suggesting potential collaborators for solving innovation challenges online, based on their competence, similarity of interests and social proximity with the user. We rely on Linked Data to derive a measure of semantic relatedness that we use to enrich both user profiles and innovation problems with additional relevant topics, thereby improving the performance of co-solver recommendation. We evaluate this approach against state of the art methods for query enrichment based on the distribution of topics in user profiles, and demonstrate its usefulness in recommending collaborators that are both complementary in competence and compatible with the user. Our experiments are grounded using data from the social networking service Twitter.com