The method of highlighting underwater objects using initiating radiation

Изложены особенности метода увеличения дальности видимости подводных телевизионных систем за счёт использования лазерных технологий. Предлагаемый метод основан на возможности усиления света в воде при пропускании его через среду с инверсной населённостью энергетических уровней. Подобная среда создаётся за счёт вспомогательного излучения, формируемого, например, лазерным излучением. Рассмотрены необходимые условия усиления света. С учётом шкалы энергий излагаются основные принципы создания инверсной населённости энергетических уровней в воде. Приведена методика расчёта дальности засветки лазерного излучателя в воде с прозрачностью 15 м, что соответствует прозрачности Баренцева моря в зимний период. Методика базируется на расчёте наблюдаемого и минимально разрешаемого (порогового) контрастов объекта поиска. Анализируются пути увеличения эффективности вновь создаваемых подводных телевизионных систем. В статье предложена концепция создания подводных световых приборов, способных существенно увеличить дальность видения систем технического зрения обитаемых и необитаемых подводных робототехнических комплексов. Актуальность работы определяется реализацией лазерных технологий при проектировании и создании подводных телевизионных систем, что представляет собой прорывное направление научно-технического прогресса и неотъемлемый элемент импортозамещения. The features of the method for increasing the visibility range of underwater television systems through the use of laser technologies are described. The proposed method is based on the possibility of amplifying light in water when passing it through a medium with an inverse population of energy levels. Such a medium is created due to auxiliary radiation generated, for example, by laser radiation. The necessary conditions for amplification of light are considered. Taking into account the energy scale, the basic principles of creating an inverse population of energy levels in water are stated. A method for calculating the exposure range of a laser emitted in water with a transparency of 15 m, which corresponds to the transparency of the Barents Seain winter, is presented. The technique is based on the calculation of the observed and minimum resolved (threshold) contrasts of the search object. The ways of the increasing the efficiency of newly created underwater television systems are analyzed. The article proposes the concept of creating underwater lighting devices that can significantly increase the range of vision systems for the technical vision of inhabited and uninhabited underwater robotic systems. The relevance of the work is determined by the implementation of laser technologies in the design and creation of underwater television systems, which represents a breakthrough in scientific and technological progress and an integral element of import substitution.

Dialogue on a superconducting laser operating via nonequilibrium inversed population

In nonequilibrium states, the entropy is reduced from its maximum thermodynamic equilibrium value by virtue of an external energy supply. Such states are characterized by a higher ordering compared to the equilibrium. Human beings represent the highest level of nonequilibrium state, at least in the known part of the Universe. Other physical systems are also well-known, for example, quantum generators, e.g., lasers. Their operation requires a high level of deviation from equilibrium called inverse population. In turn, states out of equilibrium require energy influx for their maintenance, i.e., they should be open systems. In this short review we describe in the form of dialogue between Prof. A. M. Gulian and his younger colleagues Dr. Rajendra Dulal, Dr. Serafim Teknowijoyo and Dr. Sara Chahid the task of achieving inverse population in superconductors. Then, the dialogue moves towards experimental consequences that nonequilibrium superconductors can yield. These include topics related with deeper understanding of mechanisms of superconductivity in novel materials, in particular related to the “glue” which pairs electrons in Cooper pairs. Such understanding will facilitate development of Bose-field quantum generators like lasers, and coherent acoustic as well as paramagnon quantum sources, none of which are yet realized in nonequilibrium superconductors.

Identifying the most influential features of neural population responses for information encoding and behavior

SummaryIdentifying the features of population responses that are relevant to the amount of information encoded by neuronal populations is a crucial step toward understanding the neural code. Statistical features such as tuning properties, individual and shared response variability, and global activity modulations could all affect the amount of information encoded and modulate behavioral performance. We show that two features in particular affect information: the modulation of population responses across conditions and the projection of the inverse population variability along the modulation axis. We demonstrate that fluctuations of these two quantities are correlated with fluctuations of behavioral performance in various tasks and brain regions. In contrast, fluctuations in mean correlations among neurons and global activity have negligible or inconsistent effects on the amount of information encoded and behavioral performance. Our results are consistent with predictions of a model that optimally decodes population responses, which suggests that in our behavioral tasks the readout of information is near-optimal.

The induction pumping of Coaxial Lasers on Self-Terminating Transitions

The paper presents the results of the numerical simulations of pumping a copper vapour laser by a repetitively pulsed induction (electrodeless) discharge. We have investigated the version of the laser with an annular discharge volume formed by two coaxial cylinders. Such coaxial chamber is shown to be more appropriate for the induction pumping than the conventional cylindrical chamber. In the first case, higher coupling factors in the transformercoupled circuit of the induction discharge as well as rather high curl electric field are achieved. Moreover, from the ecological point of view, the coaxial chamber appears to be safer for the surrounding personnel in terms of their exposure to electromagnetic radiation. The present work briefly presents the physical model of the laser which describes the dynamics of the plasma parameters, the kinetics of the inverse population of the working levels for the laser on self terminating transitions as well as the development of the induction radiation. The paper also presents the electrical equations describing the simplest source of electrical pump pulses. The thermal characteristics of the working medium are estimated and the design calculations of the chamber are performed. The numerical experiments have found that, in contrast to the case of a conventional copper vapour laser with aperiodic discharge, in the regarded versions of the copper vapour laser the pump pulse is realized as a train of high-frequency damped oscillations. The analysis of the physical processes occurring in the plasma of the high-frequency discharge is carried out. The pulsed behaviour of the Joule heat power is shown to release results in pronounced pulsations of the electron temperature. This fact, however, does not significantly affect the operation of the laser on self-terminating transitions. In the optimal pumping regimes, subtle oscillations are merely observed for the inverse population of the copper atom working levels and for the intensity in the radiation pulse. High output laser characteristics achieved in the numerical simulations demonstrate the potential for efficient pumping of the copper vapour laser using the inductive method which is new for such lasers.

Asymmetric double quantum wells with smoothed interfaces

We have derived and analyzed the wavefunctions and energy states for an asymmetric double quantum well (ADQW), broadened due to interdiffusion or other static interface disorder effects, within a known discreet variable representative approach for solving the one-dimensional Schrodinger equation. The main advantage of this approach is that it yields the energy eigenvalues, and the eigenvectors, in semiconductor nanostructures of different shapes as well as the strengths of the optical transitions between them. The behaviour of ADQW states for the different mutual widths of coupled wells, for the different degree of broadening, and under increasing external electric field is investigated. We have found that interface broadening effects change and shift energy levels, not monotonously, but the resonant conditions near an energy of sub-band coupling regions do not strongly distort. Also, it is shown that an external electric field may help to achieve resonant conditions for inter-sub-band inverse population by intrawell emission of LO-phonons in diffuse ADQW.