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Aiming at the engineering problem that 5G base station antenna is difficult to locate efficiently in complex electromagnetic environment, a two-stage positioning method of 5G base station antenna substation is proposed, which considers signal path loss and antenna RF radiation. Firstly, the path loss solution model of the 5G base station antenna signal in the substation is established, and the RF radiation solution model generated by the coupling excitation of 5G high-frequency electromagnetic wave and the metal shell of the electrical equipment is constructed based on the big element physical optics method. Secondly, combining the advantages of particle swarm optimization (PSO) and interior point algorithm, the antenna positioning method considering path loss and RF radiation is constructed. Among them, in the first stage, the minimum loss of 5G signal path in the substation is taken as the goal, and the antenna stations in the substation are searched globally to get the optimal pre-selected position. In the second stage, the antenna position is calibrated according to the pre-selected position, so that the interference of RF radiation is minimized, and the final position is output. Finally, a 500 kV 5G substation in Henan Province was taken as the simulation object. Compared with the original scheme, the simulation results ensured the minimum 5G path loss in the substation and took into account the electromagnetic compatibility of the equipment in the substation. The effectiveness of the location strategy for maintaining the safe operation of the substation is verified, and it can provide a reference for the 5G base station antenna positioning project of the substation. Article highlights: Considering the influence of 5G high-frequency electromagnetic wave on the electrical equipment in the substation, the positioning accuracy of 5G base station antenna in the substation is improved. The large area physical optics method can improve the calculation time and accuracy of radiofrequency radiation field intensity Combining the advantages of particle swarm optimization and interior point method, it can effectively avoid the problem of local optimal solution of location selection The simulation results show that the proposed method not only improves the location accuracy of 5G base station antennas in substations, but also applies to 5G base station antennas in more complex engineering environments [ABSTRACT FROM AUTHOR]

Single-solution-based optimization algorithms are computationally cheap yet powerful methods that can be used on various optimization tasks at minimal processing expenses. However, there is a considerable shortage of research in this domain, resulting in only a handful of proposed algorithms over the last four decades. This study proposes the Prism Refraction Search (PRS), a novel, simple yet efficient, single-solution-based metaheuristic algorithm for single-objective real-parameter optimization. PRS is a physics-inspired algorithm modeled on a well-known optimization paradigm in ray optics arising from the refraction of light through a triangular prism. The key novelty lies in its scientifically sound background that is supported by the well-established laws of physical optics. The proposed algorithm is evaluated on several numerical objectives, including 23 classical benchmark functions, the CEC-2017 test suite, and five standard real-world engineering design problems. Further, the results are analyzed using standard statistical tests to prove their significance. Extensive experiments and comparisons with state-of-the-art metaheuristic algorithms in the literature justify the robustness and competitive performance of the PRS algorithm as a lightweight and efficient optimization strategy. [ABSTRACT FROM AUTHOR]

In this paper, we introduce Riemannian warped product map as a generalization of warped product isometric immersion and Riemannian warped product submersion with examples and obtain some characterizations. First, we define Riemannian warped product map and find conditions for a Riemannian map to be Riemannian warped product map. We show that Riemannian warped product map is a composition of Riemannian warped product submersion followed by warped product isometric immersion locally. In addition, we show that Riemannian warped product map satisfies the generalized eikonal equation which is a well known bridge between geometrical and physical optics. We also find necessary and sufficient conditions for the fibers, range space of the derivative map of Riemannian warped product map and horizontal distributions to be totally geodesic and minimal. Further, we give some fundamental geometric properties for the study of such smooth maps. Precisely, we construct Gauss formula (second fundamental form), Weingarten formula and tension field. We obtain necessary and sufficient conditions for a Riemannian warped product map to be totally geodesic, harmonic and umbilical. Comparatively, we analyse the obtained results with the existing results for a Riemannian map between Riemannian manifolds. [ABSTRACT FROM AUTHOR]

The detection of weak time-dependent alternating signals in a strongly noisy background is an important problem in physics and a critical task in metrology. Quantum lock-in amplifier can extract alternating signals within extreme noises by using suitable quantum resources, which has been widely used for magnetic field sensing, vector light shift detection, and force detection. In particular, entanglement-enhanced quantum lock-in amplifier can be realized via many-body quantum interferometry. The many-body lock-in measurement provides a feasible way to achieve high-precision detection of alternating signals, even in noisy environments. In this article, we review general protocol, experiment progresses and potential applications of quantum lock-in measurements. [ABSTRACT FROM AUTHOR]

Off-axis parabolic mirrors (OAPMs) are widely used in the THz and mm-wave communities for spectroscopy and imaging applications, as a result of their broadband, low-loss operation and high numerical apertures. However, the aspherical shape of an OAPM creates significant geometric aberrations: these make achieving diffraction-limited performance a challenge, and lower the peak electric field strength in the focal plane. Here, we quantify the impact of geometric aberrations on the performance of the most widely used spectrometer designs, by using ray tracing and physical optics calculations to investigate whether diffraction-limited performance can be achieved in both the sample and the detector plane. We identify simple rules, based on marginal ray propagation, that allow spectrometers to be designed that are more robust to misalignment errors, and which have minimal aberrations for THz beams. For a given source, this allows the design of optical paths that give the smallest THz beam focal spot, with the highest THz electric field strength possible. This is desirable for improved THz imaging, for better signal-to-noise ratios in linear THz spectroscopy and optical-pump THz-probe spectroscopy, and to achieve higher electric field strengths in non-linear THz spectroscopy. [ABSTRACT FROM AUTHOR]

LiteBIRD is a future satellite mission designed to observe the polarization of the cosmic microwave background radiation in order to probe the inflationary universe. LiteBIRD is set to observe the sky using three telescopes with transition-edge sensor bolometers. In this work we estimated the LiteBIRD instrumental sensitivity using its current design. We estimated the detector noise due to the optical loadings using physical optics and ray-tracing simulations. The noise terms associated with thermal carrier and readout noise were modeled in the detector noise calculation. We calculated the observational sensitivities over fifteen bands designed for the LiteBIRD telescopes using assumed observation time efficiency. [ABSTRACT FROM AUTHOR]

Complex numbers are basic. An inconsistency would question Wigner's unreasonable effectiveness of mathematics. A vehicle to study this question is Kirchoff's scalar diffraction theory. In the paper, an inconsistency in the real phase angle of a complex number is presented. When this inconsistency is introduced in Kirchoff's theory, we can study its influence on the experimental success of this theory. There are no a priori reasons to include or exclude real phase angles. Referring to Wigner's idea of the role of mathematics in empirical science, an experiment can provide more insight. In the experiment, a weak intensity, small wavelength source can be employed. When the contradictory phase angle is excluded, a nonzero diffraction amplitude appears physically possible. If it is included, this amplitude vanishes. [ABSTRACT FROM AUTHOR]

Optics means a general area of physics that covers a broad range of topics relevant to the study of light. Optics has subfields they are quantum optics, geometrical optics, and physical optics. Photonics refers to a subset of the optics discipline. The simplicity, high efficiency, reliability, transparency, and robust feature of PID controllers were few factors behind the reasons for its acceptance and more popularity for control in processing industries globally. All the conventional techniques for PID controller design and tuning offer early workable values for reaching favorable performances. The manual tuning of the PID controller variables becomes a difficult role that needs comprehensive knowledge and expertise in that field. Certain meta-heuristic techniques are explored to design PID controllers with the main aims of attaining minimum overshoot in lesser settling time and steady state response. For accomplishing enhanced robustness, minimization of disturbance elimination, operating, and physical restraints are treated as multi-optics functions. Therefore, this article presents a modified honey badger optimization (MoHBO) algorithm-based parameter tuning of the PID controller for optics and photonics. The tuning of the PID controller with constraints on the relative delay margin was considered an optimum disturbance rejection issue and summarized the tuning process. The presented MoHBO algorithm is derived by the inclusion of oppositional based learning (OBL) with standard HBO algorithm. In addition, the MoHBO algorithm is tested using the Magnetic Levitation System (MLS) and Phase Locked Loop system (PLL) to assure the enhanced robust nature of the PID controller. A wide ranging comparison study with other metaheuristic optimization algorithms demonstrates the better performance of the MoHBO algorithm over recent algorithms. [ABSTRACT FROM AUTHOR]

In this work, the problem of radiation scattering by ice crystals typical for cirrus clouds is solved for a 94-GHz radar (wavelength 3189 µm) and a lidar (wavelength 0.355 µm); the ice refractive indices are 1.7864 + 0.0032i and 1.3249 + 0i, respectively. The scattering matrices are calculated within the physical optics approximation and the discrete dipole approximation for the case of randomly oriented particles with sizes from 4 to 1000 µm. The ratio of the radar and lidar backscattering signals in the backward direction (the so-called radar–lidar ratio) is calculated for a wide range of the particle size for typical shapes of cirrus cloud ice crystals. It is shown that this ratio can be used for estimating the size of ice crystals in cirrus clouds. [ABSTRACT FROM AUTHOR]

The report presents a solution to the problem of light scattering on randomly oriented particles of irregular shape for particles with sizes of 100, 140, 170, and 200 μm for a wavelength of 0.532 μm for various refractive indices. The solution was obtained within both the framework of the physical optics method (for the exact backscattering direction) and within the geometric optics approximation (for the scattering angles within the range from 1 to 179 deg). The obtained solutions made it possible to build a diagram of the dependence of the geometrical albedo of a particle on the maximum degree of polarization to test the Umov effect. It has been shown that if the imaginary part of the refractive index less than 0.001, the Umov effect is performed with good accuracy. However, for the case when the imaginary part of the refractive index is greater than 0.001 and the specular component of the scattered radiation begins to dominate in the solution, the Umov effect is violated. The obtained results are interesting for optical data processing. [ABSTRACT FROM AUTHOR]

The multilevel fast multipole algorithm (MLFMA) is often used to speed up the solution of surface integral equations in electromagnetics. The method makes it possible to calculate electrodynamic systems with characteristic sizes of hundreds of wavelengths on a personal computer in a relatively short time (a few hours). The paper demonstrates the use of the MLFMA together with the principle of physical optics for fast calculation of microwave radiation between the elements of the mirror transmission lines. The complexity of the calculation is O(NlogN), where N is the number of elementary parts of the mirror surfaces involved in the calculation. Thus, the calculation time for a transmission line with characteristic total mirror sizes of hundreds of wavelengths is a few minutes. By using this method, it is also possible to significantly speed up the calculation of fields in oversized transmission lines, including both waveguides and mirrors, without loss of accuracy. [ABSTRACT FROM AUTHOR]

The paper considers a physical optics model based on the Kirchhoff–MacDonald approximation taking into account re-reflections for solving electromagnetic-wave scattering problems. This model uses an integral representation of the electromagnetic field via surface currents. The paper describes an iterative algorithm in which, at each iteration step, the surface currents on the surface partition cells is determined by multiplying the influence matrix by the currents found at the previous iteration. To increase the computational efficiency of the algorithm, the influence matrix is compressed using the method of mosaic-skeleton approximations. In this case, the specificity of the matrix being approximated is taken into account by determining its elements via the matrix of the discrete representation of the integral operator, which contains the matrix of "visibility" of the partition cells. The visibility matrix indicates whether the segment connecting the centers of two cells intersects the illuminated surface at its internal points. The method was tested on model problems, which showed the applicability of the proposed algorithm to solving the problems of scattering by non-convex bodies, as well as the computational efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

Light backscattering matrices are calculated within the physical optics approximation for hexagonal atmospheric ice particles distorted in different ways for the case of arbitrary spatial orientation and single scattering. A hexagonal prism with a height of 31.62 μm and an external diameter of 22.14 μm, which is typical for "column"-type particles observed in cirrus clouds, is chosen as a basic geometric shape. Three shape distortion methods for the particles are used: tilt, convexity and concavity; the angle of distortion varies from 0° to 50° for every particle type. The wavelength of incident radiation is 1.064 μm. The calculation has shown a sharp decrease in the backscattering cross section with an increase in the angle of distortion for all particle types under study. [ABSTRACT FROM AUTHOR]

Results of studying the Umov effect for nonspherical particles large as compared to the incident radiation wavelength are presented. The study is carried out for particles with the maximum size of 100, 140, 170, and 200 µm. The results have been obtained for 210 different refractive indices whose real part varied from 1.3 to 1.6 with a step of 0.5 and the imaginary part varied within the range from 0 to 0.1344. It has been found that the Umov effect occurs for all abovementioned particles provided that the imaginary part of the refractive index is less than 0.001. [ABSTRACT FROM AUTHOR]

The scattering of electromagnetic plane waves by a perfect electromagnetic conductor is investigated. The method of physical optics is used for the analysis of the problem. The reflected fields by a whole-plane are taken into account. The surface electric and magnetic current densities are constructed with the aid of the incident wave and the reflected field from the whole-surface. The scattering integrals are obtained for the electric and magnetic vector potentials. The scattered electric and magnetic fields are expressed in terms of the vector potentials. The scattering integrals are evaluated asymptotically for large values of the wave-number. Some numerical results are given. [ABSTRACT FROM AUTHOR]

We report an experimental demonstration of positive–negative sub-wavelength interference without correlation. Typically, people can achieve sub-wavelength effects with correlation measurement no matter by using bi-photon or thermal light sources. In this paper, we adopt a thermal light source, and we count the realizations in which the intensities of the definite symmetric points are above or below a certain threshold. The distribution of numbers of these realizations which meet the restriction will show a sub-wavelength effect. With proper constrictions, positive and negative interference patterns are demonstrated. [ABSTRACT FROM AUTHOR]

We analytically study the problem of pore detection and certification in bulk objects by means of radiography. For an absorbent sample, the optimum thickness for pore imaging and detection is expressed in terms of the linear attenuation coefficient of the material. This can be used to maximize the signal-to-noise ratio by tuning the photon energy of the incident monochromatic beam. The problem is more complicated for transparent objects. An evident approach is radiography in coherent beams; in this case, we use a simple model allowing to find the field structure of the transmitted beam on the backside of the sample and beyond in the outer half space in terms of few dimensionless parameters, including the Fresnel number F = a2/λz, where a is the pore radius, λ is the wavelength, z is the distance from the back side of the sample to the detector, and the phase number Φ = akδ, with k = 2π/λ and δ being the bulk material decrement. The detailed analysis of this field structure is performed that can be used to find the optimum position of a detector revealing the pores parameters from the intensity distribution measured. We present the numerical results for a Gaussian type of the pore shape function and provide the software to calculate the space field structure for other pore shape functions. The stationary phase method in higher orders, used here to simplify the Fresnel integral, can be applied to extend the obtained results to 3D geometry. The suggested qualitative picture of the formation of images of pores as phase objects complements modern methods of monitoring porous-sensitive materials. [ABSTRACT FROM AUTHOR]

All suggested notions of reduction of two scientific theories are critically reviewed and analyzed. In particular those applied to the case of the alleged reduction of Chemistry to Quantum mechanics are examined. Since it is recognized that the weakness of this field of research is the lack of a definition of a scientific theory, it is suggested that a scientific theory is characterized by two choices regarding two dichotomies, that is, the kind of mathematics and the kind of logic. According to this view a reduction is only possible between two theories in which the same choices are shared. As a consequence, only one case of reduction in the history of physics is recognized: physical optics to electromagnetism, a case that is commonly accepted. The other cases of claimed reductions are recognized as impossible, owing to the different choices of the two theories at issue and hence the radical variations in meaning of their shared basic notions. In particular, the claimed reduction of Chemistry to Quantum mechanics is disproved in detail. [ABSTRACT FROM AUTHOR]

In various fields of photonics, there is a tendency to pass from elements of physical optics to elements of flat optics, primarily, due to a decrease in the dimensions of instruments and devices. Most frequently, spatial light modulators are used to efficiently and immediately simulate flat phase elements. In this work, we investigate the possibility of replacing a lens optical system with a computer-generated lens. The novelty of the work is a comparative analysis of the point spread functions of the lens optical system and the computer-generated lens. Numerous experiments confirm the obtained result. [ABSTRACT FROM AUTHOR]

In the physical optics approximation, we consider the backscattering of light waves by a rough surface that has a one-dimensional relief of different-scale mirror fragments and that acts as a phase screen. Asymptotic angular distributions are obtained in the diffusion phase approximation, and the numerical phase jump method is used to take into account complex statistics of surface irregularities. For a periodically modulated rough surface, the results of numerical calculations by the phase jump method and by the tangent reflecting plane method are compared with available experimental data. Angular dependences of backscattering are presented that demonstrate the effect of the Rayleigh roughness distribution on the scattering intensity, and the narrowing of the range of backscattering angles under the influence of additional large-scale random surface profiling is shown. [ABSTRACT FROM AUTHOR]

We present a novel method to characterize the radiation pattern of the terahertz photoconductive antennas in time-domain. The method uses a modified version of the terahertz time-domain spectroscopy system, where we use the basics of physical optics and the optical path compensation principle using the delay line in the system in order to detect the spatial distribution of the terahertz radiation of the photoconductive antennas in two major planes. Using this method, we investigate two terahertz photoconductive antennas, namely dipole and spiral antennas, and compare the measurement results with simulations in time-domain. The comparison of the calculation and measurement results shows good agreement, where we measure an average and maximum optical path difference error of 4.7 and 8%, which results in an average and maximum half-power beam width error of 1.87 and 3.2°, respectively. We believe that the proposed method will be useful for predicting the system level performance of the terahertz time-domain spectroscopy systems in real-life applications. [ABSTRACT FROM AUTHOR]

The extinction matrix for an ensemble of hexagonal ice plates and columns is presented. The extinction matrix for droxtal and bullet crystals has been estimated. The calculations have been carried out for particles with characteristic dimensions from 10 to 100 μm and wavelengths from 0.3 to 10 μm assuming a gamma distribution of particle size with a width parameter μ < 4. It has been found that the extinction matrix of an ensemble of atmospheric ice crystals in the visible wavelength region is a unit matrix with a coefficient equal to the doubled area of the particle projection. The error of this representation does not exceed tenths of a percent and does not depend on the type of crystals and their spatial orientation. It has also been found that such a representation of the extinction matrix in the IR region is possible only for hexagonal columns, bullets, and similar crystals with a characteristic size greater than 20 μm for wavelengths less than 8 μm. [ABSTRACT FROM AUTHOR]

A method is proposed for measuring the size of particles in a dynamic light scattering analyzer along with a determination of their number density in suspension. It is shown that this method can be used to measure the parameters of various nanoparticles, including nonspherical ones. An experimental prototype of a dynamic light scattering analyzer for measuring the number density of nanoparticles along with their sizes is described. [ABSTRACT FROM AUTHOR]

A new algorithm for solving the problem of light scattering by nonconvex crystals typical for cirrus clouds is presented. It is based on the beam tracing algorithm for convex particles (Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences). The new algorithm is applied for solving the problem of light scattering by hollow-column particles and aggregates of hexagonal ice columns. It is an opensource freely available algorithm. [ABSTRACT FROM AUTHOR]

A complex of physical optics methods that includes x-ray phase analysis, colorimetry, and wavelet analysis is proposed. Weak structural responses of dispersed clay systems to the effect of microwave radiation are recorded by means of the complex. Through the use of a combination of x-ray phase analysis and colorimetric gradation, it is possible to establish phase and polymorphic conversions, and with the use of wavelet analysis, the evolution of the morphology of dispersed particles. The efficiency of the proposed complex of physical optics methods for studying secondary phase morphologies in the millimeter, micrometric, and submicrometric scales is demonstrated. [ABSTRACT FROM AUTHOR]

The latest generation of Cassegrain radio astronomy antennas is designed for multiple frequency bands with receivers for individual bands offset from the antenna axis. The offset feed arrangement typically has two focusing elements in the form of ellipsoidal mirrors in the optical path between the feed horn and the antenna focus. This arrangement aligns the beam from the offset feed horn to illuminate the subreflector. The additional focusing elements increase the number of design variables, namely the distances between the horn aperture and the first mirror and that between the two mirrors, and their focal lengths. There are a huge number of possible combinations of these four variables in which the optics system can take on. The design aim is to seek the combination that will give the optimum antenna efficiency, not only at the centre frequency of the particular band but also across its bandwidth. To pick the optimum combination of the variables, it requires working through, by computational mean, a continuum range of variable values at different frequencies which will fit the optics system within the allocated physical space. Physical optics (PO) is a common technique used in optics design. However, due to the repeated iteration of the huge number of computation involved, the use of PO is not feasible. We present a procedure based on using multimode Gaussian optics to pick the optimum design and using PO for final verification of the system performance. The best antenna efficiency is achieved when the beam illuminating the subreflector is truncated with the optimum edge taper. The optimization procedure uses the beam's edge taper at the subreflector as the iteration target. The band 6 receiver optics design for the Atacama Large Millimetre Array (ALMA) antenna is used to illustrate the optimization procedure. [ABSTRACT FROM AUTHOR]

The study of cirrus clouds, which significantly affect the climate, is carried out using lidars. Interpretation of the lidar data is based on the direct solution of the problem of light scattering by particles of crystal clouds. Optical characteristics of perfect ice hexagonal columns, obtained previously, poorly agree with the lidar observation results. The work describes calculations of the optical characteristics of irregular hexagonal ice columns, which are in a good agreement with the experimental results. The calculations for particles with deformation of a dihedral angle of 90° are presented. It is shown that the logarithm of the scattering matrix can be linearly approximated well by the logarithm of the particle size. This can significantly accelerate the calculations of the optical characteristics of clouds. It is ascertained that the optical characteristics are in a good agreement with the lidar observation results throughout the range of sizes calculated even at deformation angles of a few degrees. [ABSTRACT FROM AUTHOR]

It is shown that, depending on the incident wave frequency and the system geometry, the extraordinary transmission of light through a metal film perforated by an array of subwavelength holes can be described by one of the three mechanisms: the 'transparency window' in the metal, excitation of the Fabry-Perot resonance of a collective mode produced by the hybridization of evanescence modes of the holes and surface plasmons, and excitation of a plasmon on the rear boundary of the film. The excitation of a plasmon resonance on the front boundary of the metal film does not make any substantial contribution to the transmission coefficient, although introduces a contribution to the reflection coefficient. [ABSTRACT FROM AUTHOR]

The results of alignment and acceptance tests of the optics system of the 2.5-m telescope installed at the Caucausus Mountain Observatory of the Sternberg Astronomical Institute in 2013-2015 are reported. The optical elements of the Ritchey-Chrétien system of the telescope were manufactured by REOSC (France). Measurements of aberrations were carried out using a specially manufactured Shack-Hartmann wavefront sensor. Adjustment of the load-distribution mechanisms of the primary mirror and automatic correction for bending of the structure have made it possible to achieve the target image quality at all operational positions of the telescope, corresponding to 80% of the energy being concentrated in a circle 0.3″ in diameter. Factory interferograms of the mirrors and methods for measuring their abberation using stellar images are presented. [ABSTRACT FROM AUTHOR]

Because circularly polarized vortex beam can be characterized as the linear superposition of radially polarized and azimuthally polarized components in the cylindrical coordinate. When investigating the focusing properties of the circularly polarized vortex beam, we must consider radially polarized vortex beam has azimuthal component and azimuthally polarized vortex beam has radial component after focusing. Due to this reason, the focusing properties of the circularly polarized vortex beams have been restudied based on the amending the tightly focusing formula of the circularly polarized vortex beam. The results show that not only the focusing of the single handedness of the circularly polarized vortex beam but also the focusing of superposition of two circularly polarized vortex beams with different topological charges and different handedness can generate the flat-top intensity shape. We also investigate the influence of amplitude ratio, waist radius and the aperture blocking on the flat-topped focus size. [ABSTRACT FROM AUTHOR]

Based on the extended Huygens-Fresnel principle, the analytical expression for the cross-spectral density (CSD) function of the radial Gaussian-Schell-model array (RGSMA) beams propagating in oceanic turbulence is derived. Then, combined with the spatial power spectrum of oceanic turbulence, analytical formulas for the average intensity and the root-mean-square (rms) beam width of the RGSMA beams propagating in oceanic turbulence are obtained. The changes of the average intensity and the rms beam width with propagation distance z and three oceanic turbulence parameters, including temperature-salinity balance parameter w, mean square temperature dissipation rate $${\chi _{\text{T}}}$$ , and energy dissipation rate per unit mass $$\varepsilon$$ , are investigated in detail. The results have certain reference value for the propagation properties of the RGSMA beams in oceanic turbulence. [ABSTRACT FROM AUTHOR]

We report plasmonic lenses consisting of coupled nanoslits immersed in a high-index medium to obtain the robustly efficient superfocusing. Based on the geometrical optics and the wavefront reconstruction theory, an array of nanoslits perforated in a gold film and a series of spacings between adjacent nanoslits are optimally designed to realize the desired phase modulation for light focusing. The numerical results verify the design of each plasmonic lens in excellent agreement. For the given total phase difference of 2π, the immersion plasmonic lenses with smaller lens aperture can have much better focusing performance than the non-immersion one. A superfocusing spot of λ/4.39 is achieved using an oil immersion plasmonic lens with an aperture size of 4.97 λ, resulting in a resolution improvement of 68.9 % compared with the non-immersion lens. Moreover, such superfocusing performance can be still well kept when the structural parameters of the lens, e.g., nanoslit width and metal film thickness, are deviated from the original design, making the final implementation of the superfocusing lenses much easier. [ABSTRACT FROM AUTHOR]

The transition from coherence to incoherence in an ensemble of nonlocally coupled logistic maps is considered. Chimera states of two types (amplitude and phase) are found. The mechanism and conditions of their appearance are determined. [ABSTRACT FROM AUTHOR]

The interaction process of electromagnetic waves by a resistive half-plane is investigated. The scattered geometrical optics fields are obtained by subtracting the incident field from the total geometrical optics waves. The physical optics integral of the scattered waves is derived with the aid of the scattered geometrical optics fields. The edge diffracted waves are derived from the physical optics integral by the edge point technique. A correction field is added to the diffracted fields in order to obtain a solution that satisfies the resistive boundary conditions on the surface of the half-screen. The uniform diffracted fields are expressed in terms of the Fresnel function and the resultant field representations are compared with the literature numerically. [ABSTRACT FROM AUTHOR]

The technique for solving the problem of light backscattering by the physical optics method is considered. Recommendations on carrying out a preliminary estimation of the contribution of geometrical optics beams are given to reduce the list of beams that are necessary for the calculation by a factor of hundreds. The presented empirical estimating formulas and recommendations on choosing the optimum step of numerical integration make it possible to considerably reduce the resource intensity of the physical optics method for specified microphysical models of hexagonal crystalline particles. The obtained results of solving the light scattering problem are freely available in the form of a databank of Mueller matrices. [ABSTRACT FROM AUTHOR]

We consider the following quasilinear Schrödinger system in $${\mathbb{R}^N}$$ with $${N\geq3}$$ : where $${D_i=\frac{\partial}{\partial x_i},\ \ D_s a_{ij}(s)=\frac{d}{ds}a_{ij}(s)}$$ , $${F(u,v)}$$ is the coupling term, $${A(x)}$$ and $${B(x)}$$ are finite and sign-changing potential functions. Using an approximation scheme and $${q}$$ -Laplacian regularization, we prove the existence of infinitely many solutions for system $${(P)}$$ . [ABSTRACT FROM AUTHOR]

Light scattering by an optically anisotropic liquid crystal (LC) droplet of a nematic in an isotropic polymer matrix is considered in the Wentzel-Kramers-Brillouin (WKB) approximation. General relations are obtained for elements of the amplitude matrix of light scattering by a droplet of arbitrary shape and for the structure of the director field. Analytic expressions for the amplitude matrices are derived for spherical LC droplets with a uniformly oriented structure of local optical axes for strictly forward and strictly backward scattering. The efficiency factors of extinction and backward scattering for a spherical nonabsorbing LC droplet depending on the LC optical anisotropy, refractive index of the polymer, illumination conditions, and orientation of the optical axis of the droplet are analyzed. Verification of the obtained solutions has been performed. [ABSTRACT FROM AUTHOR]

A modified transmission line model with the equivalent capacitors is proposed to describe extraordinary optical transmission (EOT) of the sub-wavelength slit with different inner walls. The equivalent capacitors can effectively explain the discontinuity of the interface at which the surface wave propagates. The transmittance calculated with this model is in accordance with finite difference time domain (FDTD) calculations. This modified analytical model provides a methodology to analyze the transmission properties of sub-wavelength slits with different inner walls. The results show that if well-designed and manufactured, sub-wavelength curved slits have the ability to enhance the optical transmission in the visible region or the infrared region. [ABSTRACT FROM AUTHOR]

We develop a combined method for calculating the characteristics of the integrated lens antennas for millimeter-wave wireless local radio-communication systems on the basis of the geometrical and physical optics approximations. The method is based on the concepts of geometrical optics for calculating the electromagnetic-field distribution on the lens surface (with allowance for multiple internal re-reflections) and physical optics for determining the antenna-radiated fields in the Fraunhofer zone. Using the developed combined method, we study various integrated lens antennas on the basis of the data on the used-lens shape and material and the primary-feed radiation model, which is specified analytically or by computer simulation. Optimal values of the cylindrical-extension length, which ensure the maximum antenna directivity equal to 19.1 and 23.8 dBi for the greater and smaller lenses, respectively, are obtained for the hemispherical quartz-glass lenses having the cylindrical extensions with radii of 7.5 and 12.5 mm. In this case, the scanning-angle range of the considered antennas is greater than ±20° for an admissible 2-dB decrease in the directivity of the deflected beam. The calculation results obtained using the developed method are confirmed by the experimental studies performed for the prototypes of the integrated quartz-glass lens antennas within the framework of this research. [ABSTRACT FROM AUTHOR]

The spectral properties of an electromagnetically induced grating that is based on the spatial modulation of the Raman gain in the field of a standing pump wave in a three-level homogeneous medium have been discussed. It has been shown that, by varying the intensity or the frequency of the pump field, one can control the transmission and reflection spectra, while the transmission and reflection coefficients of the probe (Raman) wave can simultaneously be greater than unity. The influence of the nonideality of the standing wave on the spectral characteristics of the grating has been studied. [ABSTRACT FROM AUTHOR]

It is shown that in optical measuring systems the errors in measuring the coordinates of an object largely depend on the image distortions, due to diffraction by the objective. An analytical estimate is given of these distortions as a function of the size of the objective, which indicates the possibility of reducing image distortions by a more accurate choice of the size of the objective and other parameters of the optical channel. [ABSTRACT FROM AUTHOR]

Theoretical and experimental investigation of the influence of the snow cover on the surfaces of reflector, in particular, parabolic reflector antennas on parameters of these antennas is performed. In the physical-Optics approximation, design relationships allowing one to estimate degradation of the antenna parameters were derived. It was experimentally confirmed that, depending on the dimensions and shape of the snow layer on the surface of a parabolic reflector, it may lower the antenna gain by 4-14 dB, increase sidelobes of the antenna pattern by 10-15 dB, and narrow down the main lobe width almost by a factor of two. [ABSTRACT FROM AUTHOR]

An analytical model to estimate the quantum efficiency and the modulation transfer function of image sensors is proposed. Proposed approach follows similar prior studies, and tries to improve them in two directions: first, the impact of internal reflections on the optical generation profile is taken into account; second, the diffusion current calculations are extended for sensors utilizing graded-epi wafers and back-side passivation implants. A back-side illuminated photo diode sensor is used as a case study to demonstrate the model response. [ABSTRACT FROM AUTHOR]

Quasihorizontally oriented ice crystals of cirrus clouds became an object of active study in recent times. Experimental observations are made with the use of multiwavelength and polarization lidars; their signals are interpreted on the basis of solutions obtained in the approximation of physical or geometrical optics. In this work, we compare these approximations for solution of the problem of light backscattering by quasihorizontally oriented hexagonal ice plates. Special attention is paid to the limits to applicability of geometrical optics approach to solution of such problems. [ABSTRACT FROM AUTHOR]

A concept of a quasi-wave method (QWM) of the order p = n − s is introduced with n and s being the total number of coordinates and the number of slow coordinates, respectively. The exact method (EM) at p = n, the parabolic equation method for 2 ≤ p < n, the QWM at p = 1, and geometric optics (GO) at p = 0 are particular cases of the QWM. It is shown for n = 3 that, under weaker assumptions, the QWM makes it possible to avoid difficulties intrinsic to the EM and GO as well as severe restrictions imposed on calculation models for GO and the theory of plane waves. [ABSTRACT FROM AUTHOR]

We design a packaged micro-optical-electromechanical system (MOEMS) - micro-grating accelerometer - that measures the interference of light resulting from its passage through a diffraction grating and reflection from the proof mass. In the present glass-silicon-glass embodiment, the diffraction optical element made of gold and the sensing proof mass supported by eight aluminum symmetrical cantilevers are fabricated on glass and silicon, respectively. Additional system components include a semiconductor laser, photodiodes, and the necessary electronics. First, we analyze the optical model to achieve high optical sensitivity. Then we optimize the structure parameters using the finite element method. Finally, we successfully fabricated the micro-grating accelerometer and packaged it in a small surface-mount package (12 × 12 × 3.6 mm). Our experiments show that the micro-grating accelerometer has a sensitivity of 5.6 V/ G in the linear operating region, a bias stability of 0.94 μG, a resolution of 5.6 μG, and a dynamic range of 82.5 dB. Such a MOEMS accelerometer integrates the micro-grating with the proof mass through an anodic bonding procedure with the advantages of small size and high resolution. [ABSTRACT FROM AUTHOR]

Characteristics of a planar double-reflector aplanatic Schwarzschild system that allow estimation of the efficiency of its application in devices of integrated microwave optics are analyzed. The results of multicriteria optimization of the system's quality indices are obtained. The aplanatic system is compared to systems with parabolic reflectors: a single-reflector system and a double-reflector system with flat subreflector. It is shown that the results of optimization obtained in the approximation of physical optics agree well with the results of the analysis and minimization of aberrations in the reflector system performed with the use of the proposed criterion of rms aberrations. Scanning characteristics of Pareto-optimal planar aplanats are presented. [ABSTRACT FROM AUTHOR]

Optical imaging through and inside complex samples is a difficult challenge with important applications in many fields. The fundamental problem is that inhomogeneous samples such as biological tissue randomly scatter and diffuse light, preventing the formation of diffraction-limited images. Despite many recent advances, no current method can perform non-invasive imaging in real-time using diffused light. Here, we show that, owing to the 'memory-effect' for speckle correlations, a single high-resolution image of the scattered light, captured with a standard camera, encodes sufficient information to image through visually opaque layers and around corners with diffraction-limited resolution. We experimentally demonstrate single-shot imaging through scattering media and around corners using spatially incoherent light and various samples, from white paint to dynamic biological samples. Our single-shot lensless technique is simple, does not require wavefront-shaping nor time-gated or interferometric detection, and is realized here using a camera-phone. It has the potential to enable imaging in currently inaccessible scenarios. [ABSTRACT FROM AUTHOR]

A laser beam shaping architecture based on a microlens array homogenizer has been exploited, in which the interference effect due to the coherency of the laser source deteriorates the uniformity. Moving diffusers have been considered as an effective way of averaging out the interference pattern. Because the uniformity is required in the line direction only, a one-dimensional reflective-type diffuser with a well-controlled diffusion angle has been proposed and prototyped. The diffuser is attached onto a rotating cylinder for movement in operation. The experiment demonstrates the effectiveness of the scheme, and a line beam with a uniformity of up to 92% has been achieved. [ABSTRACT FROM AUTHOR]