A holographic method for the design of low-loss grating couplers for optical surface waves excitation has been proposed. For a particular example of excitation of a plasmon-polariton wave in a dielectric layer on metal, the coupling efficiency of the proposed volume holograms in the dielectric layer has been analyzed in comparison with optimized periodic gratings of vertical slits in the dielectric layer. It has been shown that the coupling efficiency of the holographic gratings can exceed 90% (−0.46dB) for the vertically incident exciting Gaussian beam. The coupling efficiency of optimized periodic gratings of vertical slits in the dielectric layer was considerably lower for the same system and exciting beam parameters. The proposed method is universal: it can be applied to develop holograms for excitation of various types of waveguide modes and surface waves within dielectric and metal-dielectric structures.

Laser-assisted nanostructuring of silicon interfaces provides a unique procedure for leading-edge technologies. We report on a new embossing technique with tightly focused Gaussian-shaped ultrashort laser pulses near the ablation threshold in liquid. We take advantage of a primary microbubble for controllable spatial-modulation of light intensity of succeeding pulses. Such a bubble, generated in liquid near the molten silicon surface by the first pulse, serves as an obstacle for the second pulse following with a sub-millisecond time delay, to produce a diffraction ring pattern. Variation of laser intensity can be utilized to guide the diffraction patterns. Thus the various annular patterns deeply embossed up to hundreds nanometers on the surface are produced with high reproducibility. Morphology of modified surface layer is investigated in detail using atomic-force microscopy, as well as scanning and transmission electron microscopies. Full-wave EM modeling of laser beam diffraction by the bubbles with various radii and shapes shows that the peak intensity in silicon is up to 1.7 times higher than in bubble-free liquid. Atomistic simulation of ultrafast heating with such a diffraction peak reveals that an annular microdimple surrounded by rims is formed by high-gradient pressure in molten silicon to be frozen after several nanoseconds.

The mode of maintaining a solar orientation of spacecraft–gyrostat in low Earth orbit for a long time has been studied. The spacecraft is close to a cylinder in shape with two fixed solar arrays. The arrays are located along the longitudinal axis of the cylinder, symmetrically with respect to it. In the solar-orientation mode, the normal to the plane of the spacecraft solar arrays is invariably directed to the Sun, and the longitudinal axis oscillates relative to the plane of the orbit. To implement the specified mode of the spacecraft motion, a system of four reaction wheels is used, the rotation axes of which are directed parallel to the lateral edges of the quadrangular pyramid. The position of the lateral edges of the pyramid relative to the coordinate system rigidly connected to the spacecraft is given by two angles, which are the parameters of the reaction-wheel system. The law of control of the gyrostatic moment is considered, which ensures the attenuation of the perturbed motion of the spacecraft in the vicinity of the position of its solar orientation and limits the accumulation of the own kinetic moment of the reaction wheels by controlling the angle of rotation of the spacecraft around the normal to the light-sensitive side of the solar arrays. The study shows that with the help of a certain choice of parameters of the reaction-wheel system, it is possible to implement the solar-orientation mode without unloading the gyrostatic moment during the entire flight time. The results of numerical simulation of the complete system of equations of the spacecraft motion in the mode of its solar orientation, taking into account the influence of gravitational and aerodynamic moments, are presented, confirming the correctness of the chosen values of the parameters.

Two possible variants of the arrangement of an reaction wheel system onboard a spacecraft are considered. The first option is a system of four reaction wheels, the axes of rotation of which are parallel to the lateral edges of the quadrangular pyramid. The second option is a system of six reaction wheels, the axes of rotation of which are parallel to the lateral edges of a regular hexagonal pyramid. Each system is characterized by geometric parameters that determine the angular positions of the reaction wheels’ rotation axes. Areas of possible values of the total angular momentum created by the reaction wheel system, including in the event of a failure of one of them, are constructed. Parametric dependences are given for choosing the most rational arrangement of the reaction wheels, which provide the widest possible control over the angular velocity of the spacecraft. The mode of stabilization of the orbital orientation of the vehicle is considered, taking into account the influence of external disturbing moments. For this mode, dependences are obtained that make it possible to choose the values of the geometric parameters of the system that provide the minimum rate of accumulation of the angular momentum by each of the reaction wheels. The results of numerical simulation of the equations of motion of the spacecraft are presented.

The study is devoted to maintaining the solar orientation mode of the gyrostat spacecraft in the low earth orbit through a long period. The device shape is close to a cylinder with two fixed solar panels installed along the cylinder longitudinal axis symmetrically relative to it. In the solar orientation mode, the normal to the device solar arrays plane is invariably directed towards the Sun and the longitudinal axis oscillates relative to the orbit plane. To implement the specified spacecraft motion mode, a system of four flywheel engines is used, which rotation axes are directed in parallel to the side edges of the quadrangular pyramid. Position of the pyramid side edges relative to the coordinate system rigidly connected to the device is determined by two angles, which are the parameters of the flywheel engine system. The law of the gyrostatic moment control is considered ensuring attenuation of the perturbed spacecraft motion in the vicinity of its solar orientation and limiting accumulation of its intrinsic kinetic moment of the flywheel engines by controlling the device rotation angle around the normal to the light-sensitive side of the solar arrays. It is demonstrated that selection of certain parameters of the flywheel engines coordinate system would assist in implementing the solar orientation mode without unloading the gyrostatic moment during the entire flight time. Results of numerical simulation of the complete system of the spacecraft motion equations in its solar orientation mode are presented taking into account the influence of gravitational and aerodynamic moments, which confirms correctness of the selected parameter values.

A stimuli-responsive (pH- and thermoresponsive) micelle-forming diblock copolymer, poly(1,2-butadiene)290-block-poly(N,N-dimethylaminoethyl methacrylate)240 (PB-b-PDMAEMA), was used as a polymer template for the in situ synthesis of silver nanoparticles (AgNPs) through Ag+ complexation with PDMAEMA blocks, followed by the reduction of the bound Ag+ with sodium borohydride. A successful synthesis of the AgNPs on a PB-b-PDMAEMA micellar template was confirmed by means of UV–Vis spectroscopy and transmission electron microscopy, wherein the shape and size of the AgNPs were determined. A phase transition of the polymer matrix in the AgNPs/PB-b-PDMAEMA metallopolymer hybrids, which results from a collapse and aggregation of PDMAEMA blocks, was manifested by changes in the transmittance of their aqueous solutions as a function of temperature. A SERS reporting probe, 4-mercaptophenylboronic acid (4-MPBA), was used to demonstrate a laser-induced enhancement of the SERS signal observed under constant laser irradiation. The local heating of the AgNPs/PB-b-PDMAEMA sample in the laser spot is thought to be responsible for the triggered SERS effect, which is caused by the approaching of AgNPs and the generation of “hot spots” under a thermo-induced collapse and the aggregation of the PDMAEMA blocks of the polymer matrix. The triggered SERS effect depends on the time of a laser exposure and on the concentration of 4-MPBA. Possible mechanisms of the laser-induced heating for the AgNPs/PB-b-PDMAEMA metallopolymer hybrids are discussed.

Воздействие двух последовательных лазерных импульсов на кремний, помещенный в глицерин, исследовано экспериментально и численно с помощью программ электромагнитного, гидродинамического и атомистического моделирования. Показано, что после первого импульса на поверхности образуется микропузырек в жидкости, на котором затем происходит дифракция второго импульса, ширина светового пучка которого сравнима с диаметром микропузырька. Мы рассчитали дифракционную картину и распределение интенсивности света на поверхности кремния, и оказалось, что максимальная интенсивность в дифракционных пиках может заметно превышать интенсивность на оси падающего гауссова пучка. В результате усиления интенсивности, сконцентрированной в одном ярком узком кольце вокруг микропузырька, на кремнии образуется характерная канавка, окруженная валиками. Мы продемонстрировали в молекулярно-динамическом расчете, что интенсивный нагрев в дифракционном пике вызывает плавление и вытеснение расплава от центра прогрева. Это приводит к формированию канавок с валиками, имеющими профиль, подобный измеренному в эксперименте.

The rotational motion of an axisymmetric artificial satellite with a constant magnet under an effect of a torque produced by the Earth’s magnetic field (EMF) influence on the magnet is studied. The orbital motion of a satellite is calculated taking into account the noncentral nature of the Earth’s gravitational field and the atmospheric drag; the proper magnetic moment of a satellite is parallel to the axis of symmetry. The steady-state motions of a satellite are constructed, in which the axis of symmetry makes a small angle with the EMF intensity vector. The IGRF model is used as the EMF model. It is shown that such motions can be approximated by a sequence of periodic solutions of modified equations of motion. Steady-state motions contain two basis frequencies—the orbital and angular velocity of the Earth’s rotation. Periodic solutions have an orbital period, but the spectrum of the approximating sequence composed of them virtually coincides with the spectrum of the original steady-state mode.

Performance of plasmonic ridge waveguides of different length formed on fused silica substrates has been studied experimentally and theoretically. All the waveguides were single-mode ones, had a width of 70 μm, and their cross-section had a structure of Al2O3-Au-Al2O3 sandwich–10 nm-thick Au film deposited between 240 nm- and 70 nm-thick Al2O3 top layer and bottom layers. To shape sidewalls, the wave guiding sandwich was etched through its depth. The waveguides were terminated by 1D gratings etched in the sandwich for light coupling/decoupling. The optimized input grating had an elliptical shape for focusing plasmon waves upon excitation, and the output grating was a conventional one. It was found that the traveled plasmonic waves decoupled and visualized themselves as interference patterns in the output grating area. We study propagation of these waves for a set of waveguides with lengths of 0.5-1 mm and demonstrate their main characteristics–the propagation length and attenuation factor.

The motion of an artificial Earth satellite in different variants of the solar orientation mode in the low Earth orbit is investigated. The satellite is close in shape to a cylinder with two solar arrays. Nonrotating solar arrays are located symmetrically relative to it along the satellite's longitudinal axis. In the solar mode normal to the plane of the satellite's solar arrays invariably directed toward the Sun, the longitudinal axis lies near the plane of the orbit and the absolute angular velocity of the satellite is very small. A gyro system (a set of reaction wheels or gyrodines) is used as the decision-making centers of the satellite's control system. Two versions of the law controlling the angular momentum of the gyro system are considered. The first variant provides only the attenuation of the disturbed motion of the satellite in the vicinity of the rest position at the required speed. The second variant further limits the growth of the accumulated angular momentum of the gyro system by controlling the angle of rotation of the satellite around the normal to the plane of the solar arrays.

The possibility of stabilizing the gravitational orientation mode of a massive artificial Earth satellite (AES) by the torque produced by electromagnets interacting with Earth’s magnetic field is shown. As an example, the control of rotational motion of the satellite like Bion M-1 and Foton M-4 is considered. Control is accomplished by changing the currents in the electromagnets. The control law is considered, which provides damping of the disturbed motion of a satellite and its stabilization in the gravitational orientation mode. To form this law, it is sufficient to have the readings of a triaxial magnetometer and of an angular velocity sensor. The control law efficiency is verified by mathematically modeling satellite motion relative to the center of masses, under an effect of gravitational and aerodynamic torques, as well as the torque produced by electromagnets.

A series of long-range plasmonic waveguides based on a thin three-layer Al 2 O 3 /gold/Al 2 O 3 film operating in the visible spectral range have been studied experimentally and theoretically. For long-range plasmonic waveguides having identical structure but different lengths, the propagation length of plasmonic waves was determined to be 250 ± 15 μm at λ = 765 nm and was in a very good agreement with the theoretical value obtained through numerical modeling. The demonstrated propagation length is the highest one for the gold film-based plasmonic waveguides described in the literature for a uniform (non-photonic-crystal) substrate in the UV, visible, and near IR (up to 1 μm) spectral ranges, which is due to high technological quality of the fabricated waveguides and optimized three-layer structure. The proposed waveguides could find applications in optical interconnects and guided-wave optical sensors.

Abstract Two optical sensing elements based on the surface plasmon waves at the plasmonic-photonic-crystal/air interface, excited in the Kretschmann configuration, are proposed. The sensing elements are designed to detect air humidity and NO2 concentration in air. The angular reflectance spectra of the sensing elements are theoretically analyzed as the function of the analyte concentration. The proposed NO2-sensing element has no cross-sensitivity to humidity. The two sensing elements are based on the same multilayer metal-dielectric structure with the only exception on different gas-sensitive material layers. When combined, the sensing elements can be used to measure humidity and NO2 concentration in humid air.

Nanoplasmonic waveguides utilizing surface plasmon polaritons (SPPs) propagation have been investigated for more than 15 years and are now well understood. Many researchers make their efforts to find the best ways of using light and overcoming the speed limit of integrated circuits by means of SPPs. Here, we introduce the simulation results and fabrication technology of dielectric-metal-dielectric long-range nanoplasmonic waveguides, which consists of a multilayer stack based on ultrathin noble metals in between alumina thin films. Various waveguide topologies are simulated to optimize all the geometric and multilayer stack parameters. We demonstrate the calculated propagation length of L-prop = 0.27 mm at the 785 nm wavelength for the Al2O3/Ag/Al2O3 waveguides. In addition, we numerically show the possibility to eliminate signal cross-talks (less than 0.01%) between two crossed waveguides. One of the key technology issues of such waveguides' nanofabrication is a dry, low-damage-etching of a multilayer stack with extremely sensitive ultrathin metals. In this paper, we propose the fabrication process flow, which provides both dry etching of Al2O3/Au(Ag)/Al2O3 waveguides nanostructures with high aspect ratios and non-damage ultrathin metal films patterning. We believe that the proposed design and fabrication process flow provides new opportunities in next-generation photonic interconnects, plasmonic nanocircuitry, quantum optics and biosensors.

Angular motion of an axisymmetrical artificial satellite with a permanent magnet in the real magnetic field of the Earth was investigated. The satellite orbit was calculated taking into account the major perturbing factors, and the satellite dipole moment was parallel to the axis of symmetry. Satellite stationary motions were constructed, where this axis constituted a narrow angle with the Earth's magnetic field vector. Possibility was demonstrated of approximating such motions by a sequence of periodic solutions of modified motion equations. Sequence composed of such solutions also approximated the spectrum of stationary motion.

Methods of fabrication of precisely adjusted surface structures are indispensable to development of new technologies. Different surface structuring techniques resulting in solitary nanobumps, random surface structures and laser induced periodic surface structures were in focus in the past. Here we consider a physical model and numerical simulation allowing understanding a high field plasmonics formation process of a smooth periodic perturbation of surface on a metal film with a period equal to the surface plasmon-polariton wavelength at a frequency of laser wave. Such surface structure is a hologram produced by thermomechanical response to interference between an incident laser wave, a reflected laser wave, and an electromagnetic field in the running plasmon-polariton wave. The following laser irradiation of the manufactured hologram generates a new plasmon-polariton wave identical to that used for formation of the hologram.