Dissipative parametric modulation instability and pattern formation in nonlinear optical systems

We present the essential features of the dissipative parametric instability, in the universal complex Ginzburg- Landau equation. Dissipative parametric instability is excited through a parametric modulation of frequency dependent losses in a zig-zag fashion in the spectral domain. Such damping is introduced respectively for spectral components in the +ΔF and in the -ΔF region in alternating fashion, where F can represent wavenumber or temporal frequency depending on the applications. Such a spectral modulation can destabilize the homogeneous stationary solution of the system leading to growth of spectral sidebands and to the consequent pattern formation: both stable and unstable patterns in one- and in two-dimensional systems can be excited. The dissipative parametric instability provides an useful and interesting tool for the control of pattern formation in nonlinear optical systems with potentially interesting applications in technological applications, like the design of mode- locked lasers emitting pulse trains with tunable repetition rate; but it could also find realizations in nanophotonics circuits or in dissipative polaritonic Bose-Einstein condensates

Волокнистая масса для изготовления офортной бумаги

У статті розглядається можливість використання модифікованих волокон на основі целюлози, як добавку, в композиційному складі волокнистої маси при виготовленні паперу для друку офортів.In the article the possibility of the use of the modified fibres on the basis of cellulose is considered, as addition, in composition of fibred mass at making of paper for printing of etching.В статье рассматривается возможность использования модифицированных волокон на основе целлюлозы, как добавку, в композиционном составе волокнистой массы при изготовлении бумаги для печати офортов

Investigating optical complexity of the phase transition in the intensity of a fibre laser radiation

Fibre lasers have been shown to manifest a laminar-to-turbulent transition when increasing its pump power. In order to study the dynamical complexity of this transition we use advanced statistical tools of time-series analysis. We apply ordinal analysis and the horizontal visibility graph to the experimentally measured laser output intensity. This reveal the presence of temporal correlations during the transition from the laminar to the turbulent lasing regimes. Both methods allow us to unveil coherent structures with well defined time-scales and strong correlations both, in the timing of the laser pulses and in their peak intensities

Self-Induced Faraday Instability Laser

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modelin

In-cavity pulse shaping and dissipative parametric instability mode-locking in fibre lasers

At the level of fundamental research, fibre lasers provide convenient and reproducible experimental settings for the study of a variety of nonlinear dynamical processes, while at the applied research level, pulses with different and optimised features – e.g., in terms of pulse duration, temporal and/or spectral shape, energy, repetition rate and emission bandwidth – are sought with the general constraint of developing efficient cavity architectures. In this work, we review our recent progress on the realisation of pulse shaping in passively- mode-locked fibre lasers by inclusion of an amplitude and phase spectral filter into the laser cavity. We present a fibre laser design in which pulse shaping occurs through filtering of a spectrally nonlinearly broadened pulse in the cavity. This strategy of pulse shaping is illustrated through the numerical demonstration of the laser operation in different pulse-generation regimes, including parabolic, flattop and triangular waveform generations, depending on the amplitude profile of the in-cavity spectral filter [1]. As an application of this general approach, we show that the use of an in-cavity flat-top spectral filter makes it possible to directly generate sinc-shaped Nyquist pulses of high quality and of a widely tunable bandwidth from the laser [2]. We also report on a recently-developed versatile erbium-doped fibre laser, in which conventional soliton, dispersion-managed soliton (stretched-pulse) and dissipative soliton mode-locking regimes can be selectively and reliably targeted by programming different group-velocity dispersion profiles and bandwidths on an in-cavity programmable filter [3]. Further, we report on our recent results on the passive mode locking of a Raman fibre laser by a recently predicted new type of parametric instability – the dissipative Faraday instability [4], where spatially periodic zig-zag modulation of spectrally dependent losses can lead to pattern formation in the temporal domain. High-order harmonic mode locking is achieved in a very simple experimental configuration, with the laser cavity including an optical fibre and two chirped fibre Bragg gratings, and no additional mode-locking elements. The results not only open up new possibilities for the design of mode-locked lasers, but extend beyond fibre optics to other fields of physics and engineering. References [1] S. Boscolo, C. Finot, H. Karakuzu, P. Petropoulos, “Pulse shaping in mode-locked fiber laser by in-cavity spectral filter,” Opt. Lett., vol. 39, pp. 438–441, 2014. [2] S. Boscolo, C. Finot, S. K. Turitsyn, “Bandwidth programmable optical Nyquist pulse generation in passively mode-locked fiber laser,” IEEE Photon. J., vol. 7, 7802008(8), 2015. [3] J. Peng, S. Boscolo, “Filter-based dispersion-managed versatile ultrafast fibre laser,” Sci. Rep., 2016, In press. [4] A. M. Perego, N. Tarasov, D. V. Churkin, S. K. Turitsyn, K. Staliunas, “Pattern generation by dissipative parametric instability,” Phys. Rev. Lett., vol. 116, 028701, 2016

Автоматизация определения оптических характеристик фотополимерных композиций УФ-лаков и лакированных оттисков

Розроблено структуру системи для автоматизації вимірювання і статистичного визначення коефіцієнта пропускання і оптичної густини фотополімерних композицій УФ-лаків і лакованих відбитків із застосуванням программно-апаратних засобів з проблемною орієнтацією.The structure of the system is developed for automation of measuring and statistical determination of coefficient of admission and optical closeness of photopolimer compositions of ultraviolet varnishes and lacquered prints with the use of software and hardware facilities with the problem orientation.Разработана структура системы для автоматизации измерения и статистического определения коэффициента пропускания и оптической плотности фотополимерных композиций УФ-лаков и лакированных оттисков с применением программно-аппаратных средств с проблемной ориентацией

ナサニエル・ホーソーン作品に見る無意識の諸相(2) : 「ジョン・イングルフィールドの感謝祭」の一考察

ナサニエル・ホーソーンの作品は， 歴史， 宗教， ジェンダーなど多様な視点からのアプローチを許容するが， 筆者にとっては C・G・ユングの心理学を通して， 個々の人物や事件の象徴性や元型イメージの読解ばかりでなく， エーリッヒ・ノイマンの理論 １に準拠してそれらのパーツを組み合わせ， 元型的意識発達過程と照合することが有効に思われる． 前稿 ２では短編 「シルフ・エサリッジ」 のヒロインの心理や登場人物の意味を読解したが， 本稿ではユング心理学の 「影」３ や二重人格の病理などの理論をも援用し， 短編 「ジョン・イングルフィールドの感謝祭」 について作中には述べられていないヒロインの堕落の原因を究明し， 一時的な家庭への帰還の意味を考えてみたい． そうすることによってホーソーン作品の女性像全般への理解を一層深めることができると考えられるからである

Studies of Modern Star Catalogs Based on Photoelectric Observations of Lunar Occultations of Stars

© 2018, Pleiades Publishing, Ltd. An important area of investigation in astronomy is the relationship between fundamental and dynamical coordinate systems. Valuable material for such studies is provided by photoelectric occultation observations of stars by the Moon, which can provide high precision of detecting rapidly occurring processes and have been carried out over a long time interval. This latter feature is especially important for analyses of the stellar propermotions dynamics. A method has been developed to use photoelectric occultation observations to determine the orientation and rotational parameters of the axes of the coordinate system used for modern star catalogs relative to the coordinate axes of a highly accurate dynamical ephemeris of theMoon. A complete database of photoelectric occultation observations has been created for this purpose, containing data for 57 365 events. The combination of photoelectric occultation observations and other astronomical observations such as lunar laser-ranging data enables the highly accurate determination of parameters of the Moon’s dynamics, such as systematic errors in catalog coordinate systems, including various geodetic reference systems. The parameters of shifts and the rotation of the axes of the Hipparcos Celestial Reference Frame relative to the DE421 dynamical system are obtained. This paper is based on a talk given at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017)

The fractal method for analysis of macro models of the celestial bodies surface

© 2016, Education and Upbringing Publishing. All rights reserved.In case of building a model of physical surface of celestial body scientists are dealing with a system of parameters whose precision depends on an order of spherical functions series expansion. For significant precision a complicated figure forms and it is almost impossible to describe that with the classical approach. Thereby conducting a comparative analysis of the classical models built on the basis of various observations is quite complicated. The aim of this work is to apply a fractal analysis for topographic and selenographic models investigation. The approach based on fractal similarity of physical structures was used for classical models and models of the librational zone of the Moon, that had been built by expansion in a series of spherical functions in the dynamical coordinate system. As a result, the fractal dimensions of the librational zone of the Moon determined for the mentioned models at various angles have been obtained

Lorentzian' analysis of the accuracy of modern catalogues of stellar positions

© Published under licence by IOP Publishing Ltd. There is a new approach for the estimation of the position accuracy and proper motions of the stars in astrometric catalogues by comparison of the stars' positions in the researched and Hipparcos catalogues in different periods, but under a standard equinox. To verify this method was carried out the analysis of the star positions and proper motions UCAC2, PPM, ACRS, Tycho-2, ACT, TRC, FON and Tycho catalogues. As a result of this study was obtained that the accuracy of positions and proper motions of the stars in Tycho-2 and UCAC2 catalogues are approximately equal. The results of the comparison are represented graphically