Optical ratchets with discrete cavity solitons

We propose a setup to observe soliton ratchet effects using discrete cavity solitons in a one-dimensional array of coupled waveguide optical resonators. The net motion of solitons can be generated by an adiabatic shaking of the holding beam with zero average inclination angle. The resulting soliton velocity can be controlled by different parameters of the holding beam.Comment: 3 pages, 4 figures, submitted to Optics Letter

Brillouin dynamic gratings in optical fibres for distributed sensing and advanced optical signal processing

This thesis presents results of a research on applications of Brillouin dynamic gratings - distributed reflectors that can be dynamically created in an optical fibre by two optical waves. A basic theory of stimulated Brillouin scattering (SBS) is introduced, on a level enough for understanding the processes that govern SBS. A major part of this thesis is dedicated to studies of distributed Brillouin sensors based on phase correlation. First, the concept of correlation-based sensors is introduced - the commonly used Brillouin optical correlation-domain analysis (BOCDA) and the phase-correlation technique. It is described how the Brillouin interaction between two waves can be localised, creating a permanent reflector confined to a centimetre-scale section of the fibre. This allows creating a distributed sensing system with very a high spatial resolution. A detailed theoretical model for the phase-correlation technique is presented, showing how the gain response of a system can be calculated and how the system resolution can be determined. For an ideal case an analytical solution is derived, while for real experimental conditions the expected behaviour is found via numerical simulation. Results of numerical modelling are compared with experimentally obtained data, showing a good agreement. A spatial resolution of 1 cm is demonstrated over a 200 m distance representing 20000 separate points. The concept of time gating is introduced, extending the measurement distance from 200 m to 17.5 km while retaining a sub-centimetre spatial resolution. This technique allows for a two order of magnitude increase in the number of points that a system is capable to resolve. An absolute record for distributed fibre sensors is achieved, demonstrating a system capable to resolve 2100000 separate points. Limitations for a further increase in number of points are discussed as well as possible ways to overcome them. An issue related to the temperature dependency of the refractive index is discussed in details, since it can lead to significant errors in spatial accuracy. An algorithm is presented that is capable of using the measured temperature change to account for the change in the refractive index and correctly determine the positioning of measured data. In the last chapter potential applications of Bragg dynamic gratings in signal processing are investigated. A theoretical model of BDG's in polarisation-maintaining fibres is presented capable of calculating reflection of a probe wave - continuous or pulsed. The model includes the case of non-uniform birefringence along the fibre. Dynamic gratings are applied to create a flip-flop - an all-optical memory, turned on and off by a light pulse. A working system is demonstrated in a 1 m long fibre, corresponding to a 10 ns storage time. Using the theoretical model the birefringence variation is measured along the fibre. A preliminary study of spectral properties of dynamic gratings is presented, along with a model predicting the spectrum of a uniform BDG. It is demonstrated that the spectral properties of a BDG can be manipulated by changing the spectra of optical waves used in the generation process. This work is concluded by a discussion, summing up the above-mentioned theoretical the experimental work. Potential applications of the presented research are proposed along with the most promising direction of further research activities

Radiometric Imaging for Monitoring and Surveillance Issues

This paper deals with the recent advances performed by State Research Center “Iceberg” (SRC) in the field of the passive imaging at millimeter wavelengths. In particular, first the paper describes the design and the realization of two systems working in 3 mm and 8 mm wave bands, respectively. Second, the measurements collected by the two systems are enhanced by means of simple data processing strategies developed by the Institute for Electromagnetic Sensing of the Environment (IREA-CNR)

Brillouin distributed fiber sensing at ultra-high spatial resolution

Sophisticated techniques have been recently developed to achieve centimetric spatial resolution in distributed Brillouin fibre sensing, by-passing the slow response of this optoacoustic interaction by creating a localized stationary material vibration. More than 1'000'000 resolved points are demonstrated (1 cm resolution over 10 km)

Going beyond 1000000 resolved points in a Brillouin distributed fiber sensor: theoretical analysis and experimental demonstration

Distributed fiber sensing possesses the unique ability to measure the distributed profile of an environmental quantity along many tens of kilometers with spatial resolutions in the meter or even centimeter scale. This feature enables distributed sensors to provide a large number of resolved points using a single optical fiber. However, in current systems, this number has remained constrained to a few hundreds of thousands due to the finite signal-to-noise ratio (SNR) of the measurements, which imposes significant challenges in the development of more performing sensors. Here, we propose and experimentally demonstrate an ultimately optimized distributed fiber sensor capable of resolving 2100000 independent points, which corresponds to a one-order-of-magnitude improvement compared to the state-of-the-art. Using a Brillouin distributed fiber sensor based on phase-modulation correlation-domain analysis combined with temporal gating of the pump and time-domain acquisition, a spatial resolution of 8.3[thinsp]mm is demonstrated over a distance of 17.5 km. The sensor design addresses the most relevant factors impacting the SNR and the performance of medium-to-long range sensors as well as of sub-meter spatial resolution schemes. This step record in the number of resolved points could be reached due to two theoretical models proposed and experimentally validated in this study: one model describes the spatial resolution of the system and its relation with the sampling interval, and the other describes the amplitude response of the sensor, providing an accurate estimation of the SNR of the measurements

The quality assurance system of the trusted Microelectronic production

Trust (in reliable and safe operation) in a microelectronics product is mainly «laid down» at the stage of its development and is managed by guarantees of quality and reliability, the developer's qualifications and experience, a rational choice of key technical solutions that implement specified functional and operational characteristics, as well as parrying the main threats to its safety. Similarly, trust in products during their pilot and mass production is managed by the results of effective interaction and a rational combination of two systems: (1) managing the quality and protection of the manufacturer of products (i.e., using trusted processes) and (2) controlling production batches and samples of finished products (i.e., checking the reliability of a complex of technical means). This interaction implements a mutual «transfer of trust» to production processes and finished products – the possibility of spreading trust in production processes to trust in finished products and vice versa. At the stage of mass production, it is necessary first of all to ensure the stability of functional and operational characteristics, as well as acceptable technical and economic indicators of the product while maintaining the quality and protection levels inherent in its development. The article presents the results of an analysis of the critical stages of the microelectronics products production, typical threats arising at these stages, and methods of their parrying. There results allow us to build trust in such products (trust in their reliability and quality)

Random-access distributed fiber sensing

Optical sensing offers an attractive solution to the societal concern for prevention of natural and human-generated threats and for efficient use of natural resources. The unprecedented properties of optical fibers make them ideal for implementing a ‘nervous system’ in structural health monitoring: they are small, low-cost and electrically and chemically inert. In particular, the nonlinear interaction of stimulated Brillouin scattering allows for the distributed measurement of strain and temperature with tens of km range. In this work, a novel, radar-inspired technique for random-access Brillouin scattering-based sensors is shown, making a significant step towards a real optical sensing nerve. The method selectively addresses each fiber segment as a distinct sensing element in a synaptic neuronal system. The measurement principle relies on phase-coding of both the Brillouin pump and signal waves by a high-rate, pseudo-random bit sequence. Temperature measurements with 1 cm resolution are reported. The measurement range is scalable to several km

Наноалмазные коллективные электронные состояния и их локализация

The collective states despite their importance are rarely used to describe the electron structure of dielectric materials. The nature of the unrelated to impurities unpaired spins found experimentally in the nanodiamond is still under discussion. We propose the explanation of their nature in terms of the collec- tive electron states. Collective states are studied by solving a one-particle one-dimensional Schr¨odinger equation in the Kronig–Penney potential and by ab initio computations of ground state wavefunctions of diamondoids C78H64, C123H100 and C211H140 at the DFT R-B3LYP/6-31G(d,p) level of theory. Three distinct classes were found: collective bonding states resembling modulated particle in a box solutions; surface-localized non-bonding conductive Tamm states and subsurface-localized bonding states for nonuniformly compressed nanodiamond. The existence of the unpaired spins is supposed to result from the spin-density fluctuation effects significant on the nanoscale collective and spread subsurface statesКоллективные электронные состояния, несмотря на их важность, редко используются для описания электронной структуры диэлектриков. Природа не связанных с примесями неспаренных спинов, наблюдаемых экспериментально в наноалмазе, всё ещё обсуждается. Мы предлагаем описание их природы в терминах коллективных электронных состояний. Коллективные состояния исследованы точным решением одночастичного одномерного уравнения Шрёдингера в потенциале Кронига Пенни и первопринципными расчетами волновых функций основных состояний для алмазоидов C78H64, C123H100 и C211H140 методом DFT R-B3LYP/6-31G(d,p). Найдены три различных класса: коллективные связывающие орбитали, соответствующие модулированным решениям для частицы в потенциальной яме; поверхностные несвязывающие проводящие состояния Тамма и подповерхностные связывающие состояния для неоднородно сжатого наноалмаза. Существование неспаренных спинов предположительно объясняется флуктуациями спиновой плотности, значительными для наноразмерных коллективных и протяженных подповерхностных состояний