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In this paper, we present the parallel computation of physical electromagnetic (EM) solvers, namely physical optics (PO), shooting and bouncing rays (SBR), and the physical theory of diffraction (PTD), which are used for EM scattering/diffraction calculations. The accelerated solvers have been tested on CPU and GPU kernels for significantly faster calculation times. As an application, the developed implementation is employed to recently developed tool of PREDICS that uses combined techniques PO, SBR, and PTD for the calculation of EM scattering/diffraction and radar cross section (RCS) from electrically large, complex objects. First, the CPU parallelization of these three combined techniques on the PREDICS code is explained. The parallelization implementation is specially tailored for the nature of SBR technique such that the CPU iteration loop is accomplished over triangular facets of the CAD file by employing a read/write spin lock task dispatching technique. Next, a lock-free implementation of the PO, SBR, and PTD techniques on the GPU threads is presented. Thanks to availability of many GPU cores, the parallelization procedure is widened such that triangular facets, observation angles of elevation and azimuth are used for a much faster calculation set-up. Numerical examples for the EM/RCS calculation of simple canonical and electrically big, complex objects are shared to demonstrate the effectiveness, accuracy and the computational acceleration based on the multi-CPU and multi-GPU implementations. The key metric of the contribution of the study is the speed-up value of the implementations. The acceleration gained via multi-CPU realization yielded directly in parallel with the number of available CPU cores. On the other hand, the acceleration factor can reach to hundreds when multi-GPUs are used. In fact, the acceleration factor has reached to 4.7 for a machine with 4 Core 8 Thread CPU processor, and 141.3 for a 2560 CUDA GPU Core system. [ABSTRACT FROM AUTHOR]

A physical-optics hybrid method designed for the computation of single-scattering properties of particles with complex shapes, including surface roughness, is presented. The method applies geometric optics using a novel ray backtracing algorithm to compute the scattered field on the particle surface. A surface integral equation based on the equivalence theorem is used to compute the scattered far-field, which yields the full Mueller matrix and integrated single-scattering parameters. The accuracy is tested against the discrete dipole approximation for fixed orientation smooth and roughened compact hexagonal columns for 3 values of refractive index. The method is found to compute asymmetry parameter, and scattering and extinction efficiencies with mean errors of − 1. 0 % , − 1. 4 % , − 1. 2 % , respectively, in a computation time reduced by 3 orders of magnitude. The work represents a key step forwards for modelling particles with physical surface roughness within the framework of physical-optics and provides a versatile tool for the fast and quantitative study of light scattering from non-spherical particles with size much larger than the wavelength. • Physical-optics hybrid light scattering code for large particles with roughness. • Novel ray back-tracing algorithm and vector diffraction theory at an aperture. • Far field obtained by sum of transmission, reflection, and external diffraction. • Simulation tool for 2-d scattered field and single-scattering parameter computation. [ABSTRACT FROM AUTHOR]

Size measurement of micron-sized metal droplet is of great demand in industrial applications, e.g., 3D printing and metal propellant. A dual-beam interferometric particle imaging (DIPI) technique is developed to measure the size of opaque metal droplet, which is adapted from the traditional interferometric particle imaging (IPI) for transparent particles. In DIPI, the studied metal droplet is illuminated by two laser beams from different views, and the laser beams are reflected on the surface of the droplet. An interference pattern of the two reflections is yielded in the far-field that was capable to derive the size of aim droplet. The principle of DIPI is formulated in the framework of physical optics, with system configuration, modeling and data processing algorithm presented. A DIPI system is established to characterize the gallium droplet with size ranging from 300 μ m to 500 μ m experimentally, and the measured sizes with DIPI is compared with those obtained simultaneously by digital inline holography, which is a standard tool for particle measurement. Comparison shows that the measurements with these two methods are highly consistent, with a standard deviation of 1.7%. DIPI has been demonstrated with high measurement accuracy and flexible implementation of the one-sided arrangement. Unlabelled Image • Dual-beam interferometric particle imaging (DIPI) is developed for size measuring. • Measurement principle of DIPI is theoretically derived. • DIPI coupled with digital inline holography is applied to measure gallium droplets. [ABSTRACT FROM AUTHOR]

A unique approximation to the vectorial Rayleigh–Sommerfeld diffraction integrals (RSDI) is developed to study the diffraction properties of apertures illuminated with collimated, converging or diverging polarized waves. The apertures can be bigger or smaller than the wavelength of the illumination light. For circular apertures, it is shown that the approach can be expressed as a simple set of equations containing one-dimensional integrals. • A single approach to study RSDI of collimated, convergent or divergent waves. • Accurate approach, as good as the best performance of other approaches. • Set of 1D integrals to study the RSDI for the most general form of light polarization. • Demonstration that the new approach introduces the lowest errors of Taylor based approaches. [ABSTRACT FROM AUTHOR]

This paper presents an optical method to determine the scattering characteristics of dielectric rough targets in the terahertz band. Based on the complex permittivity of alloy Al (Aluminum) and painted Al obtained from the reflectance spectra, the analytical bidirectional reflection distribution function (BRDF) spectra of rough surfaces are simulated using physical optics. The effects of surface roughness, complex permittivity, incident angle, and wavelength are analyzed. With the optimization of artificial immune network genetic algorithms, it is demonstrated that the optimized five-parameter BRDF empirical model fits the analytical BRDF spectra over a wide range of incidence angles. Then, the radar cross section (RCS) of electrically large targets can be simulated by the relationship between the differential scattering coefficient and BRDF. The obtained RCS of the rough sphere from optimized BRDF model is in good agreement with the numerical analysis that was obtained. The proposed method is suitable for obtaining the scattering properties of large dielectric targets with different surfaces compared with traditional high-frequency electromagnetic (EM) techniques. The backscattered and bistatic terahertz RCS of a cylinder, cone and NASA almond are simulated. The proposed method shows the potential for the application of BRDF in the areas of scattering analysis and remote sensing. [ABSTRACT FROM AUTHOR]

For the integrated stealth issue of ducted tail rotor noise radiation and radar scattering, a comprehensive optimization method based on high frequency electromagnetic calculation theory and boundary element method is introduced. The radar cross section of the rotor, radiated noise and radar cross section of the ducted tail rotor are designed as optimization goals under the constraints of geometric parameters and aerodynamic force. The model of the ducted tail rotor is established by using the full factorial design and the flow field is constructed by high-precision unstructured grid technology. The aerodynamic characteristics of the ducted tail rotor is simulated by the computational fluid dynamics method based on Navier–Stokes equations and k – ε standard viscous model. The noise radiation is solved by boundary element method and the radar cross section value is calculated by physical optics method and physical theory of diffraction. On the basis of these calculation results, the optimization model of the ducted tail rotor is obtained and generated by comprehensive optimization method based on Pareto solution. The final scheme has been satisfactorily improved in terms of noise suppression, radar cross section reduction and aerodynamic lifting. The proposed approach is very effective and efficient for the acoustic/radar comprehensive stealth design of the ducted tail rotor. [ABSTRACT FROM AUTHOR]

Flying wing layout has both favorable aerodynamic performance and outstanding radar scattering characteristics, which is regarded as an ideal stealth aircraft layout. In this paper, a gradient-based aerodynamic and stealth optimization design method is established by coupling the Free-Form Deformation approach (FFD), Radial Basis Function algorithm (RBF), Computational Fluid Dynamics (CFD), Physical Optics (PO) and the Sequential Quadratic Programming algorithm (SQP). The gradient of the aerodynamic characteristic parameters could be obtained by solving the discrete adjoint equations. With PO code differentiated by the automatic differentiation tool, the Radar Cross Section (RCS) and its gradient would be collected. Based on the aero-stealth optimization design method, three kinds of optimization strategies are applied to design a certain flying wing layout aircraft: 1) The drag coefficient is chosen as the objective function while the RCS is set as a constraint condition; 2) The RCS is selected as the objective function while the drag coefficient is set as a constraint condition; 3) The objective function is composed of the drag coefficient and the RCS through the Weighted Sum method. The optimization results show that when choosing the first two strategies, the optimization algorithm would push single discipline performance to the edge. Alternatively, it would obtain several trade-off configurations when selecting the last strategy. The results demonstrate that the gradient-based aero-stealth optimization design method can deal with the multidisciplinary optimization problems which require a large number of design variables. Without a large number of function evaluations, this method could rapidly and efficiently obtain the shape that meets the requirements of aerodynamic and stealth performances. [ABSTRACT FROM AUTHOR]

The EC-system of the TCV tokamak is progressively being upgraded with the addition of two MW-class dual-frequency gyrotrons (84 and 126 GHz/2s/1MW). In order to connect the two gyrotrons to the existing low field side and top launchers, new waveguide routing from gyrotron hall to TCV tokamak was designed and dedicated Matching Optics Units (MOU) have been developed. The internal optics of the system have been determined aiming at optimal coupling to the HE 11 waveguides. The laws of quasi-optics were used to find quadratic surfaces to shape an incoming Gaussian beam representative of the gyrotron output into a beam matching the proper field distribution at the waveguide entrance and with HE 11 content compatible with the system requirements. A solution with one flat (movable) mirror and two shaping mirrors was found and characterized with the physical optics code GRASP. The resulting field distribution is then truncated and projected onto the HE 11 component to evaluate the design solution (coupled power at the waveguide entrance >98.4% and HE 11 content >96.8% for both frequencies). The model and the results of this analysis will be presented and compared to a model based on the Rayleigh–Sommerfeld scalar diffraction integral. GRASP was also used to evaluate preliminary misalignment effects in terms of coupled power to the waveguide and the MOU design moved to the manufacturing phase. In parallel to the gyrotron integration and to extend the level of flexibility of the TCV EC-system, a modular closed divertor chamber is developed, requiring the X3 top-launcher to be redesigned. Preliminary antenna conceptual design studies including new curvature to cope with the requirements of modularity and flexibility will be presented. [ABSTRACT FROM AUTHOR]

• We propose a simple method to controllably enhance the absorbance and the optical responsivity of devices based on two-dimensional mechanical resonators. • Our method consists in shining monochromatic light on the device at oblique incidence and measuring the intensity of reflected light. • For s-polarized light, absorbance and optical responsivity strongly increase with increasing incidence angle. Optical reflectometry is a well known technique employed to measure the displacement response of mechanical resonators. This technique consists in shining monochromatic light on the resonator at normal incidence and measuring the intensity of reflected light. In the case of resonators fabricated from suspended membranes of two-dimensional materials, fluctuations of distance between the membrane and the underlying substrate are transduced into fluctuations of reflected light intensity. Here we consider an alternate configuration where we shine light at oblique incidence. Within the plane wave model, we calculate the absorbance of the membrane, the reflectance of the device composed of the membrane and the reflective substrate, and the optical responsivity defined as the derivative of reflectance with respect to membrane displacement. We illustrate our calculations with the example of a resonator based on monolayer molybdenum disulfide and find that these quantities can be tuned by changing the angle of incidence, especially in the case of s-polarized light. These results may serve to design experiments where the absorbance and optical responsivity of the resonator are tuned by tilting the device. [ABSTRACT FROM AUTHOR]

• Optimized multiple lookup tables (Multi-LUTs) for improving computing efficiency and estimation accuracy. • Multi-LUTs method based on the N-PROSAIL model for canopy nitrogen density estimation. • Canopy nitrogen density estimation from field and UAV hyperspectral data. Unmanned aerial vehicle (UAV) based hyperspectral images linked to a radiative transfer model can provide a promising approach for high throughput monitoring of plant nitrogen (N) status. In this study, multiple lookup tables (Multi-LUTs), each LUT corresponding to one growth stage, were constructed based on the N-PROSAIL model, a radiative transfer model, and LUT size was optimized for improving computing efficiency. The objective is to use the constructed Multi-LUTs for estimating canopy N density (CND) in winter wheat. Results suggest that Multi-LUTs of leaf area index, leaf N density and two spectral indices (MSR and MCARI/MTVI2) in winter wheat demonstrate good performance of CND estimation; and LUTs with the optimal size of 6000 rows can yield good accuracy. The R2 and nRMSE values of the regression relationship between estimated and measured CND were 0.83 and 0.23 from field hyperspectral data, and 0.69 and 0.27 from UAV based hyperspectral imagery during the 2014–2015 growing season. CND by Multi-LUTs method was also accurately estimated from field hyperspectral data during the 2013–2014 growing season, with R2 and nRMSE values of 0.74 and 0.26. The estimation accuracy of CND based UAV data was a slightly lower than based field data. The resultant thematic CND map accurately exhibits CND variability at varying spatial and temporal scales. Results from this study confirmed the potential of combining UAV based hyperspectral imagery and physical optics approach for estimating CND in winter wheat. [ABSTRACT FROM AUTHOR]

Abstract Twisting behaviors of the optical vortices and the intensity patterns of a strongly focused, circularly polarized field with two off-axis vortices are investigated in this article. The transverse focal shift (TFS) which is mainly caused by the off-axis vortices and the strong focusing effect is also studied. It is very interesting to find that in the focal region the two off-axis vortices can coil many circles with each other as the beam propagates, and their trajectories form a double helical structure. Three factors for this twisting behavior are analyzed. It is also found that the intensity maxima of the total field are not strongly influenced by the twisting behavior of the vortices and rotate only a quarter circle (90°) to the focal plane. In contrast to the TFS in the linearly polarized field, the 'actual focus/foci' in this circularly polarized field does/do not move between the + y s axis and the − y s axis or the y s axis and the x s axis, but is/are always confined on the + y s ∕ y s axis. These results will be useful in understanding the general rotational behaviors in optical fields with off-axis vortices and can have applications in optical manipulations. [ABSTRACT FROM AUTHOR]

Highlights • Moiré fringe is used for proximity lithography. • Complex mark consists of coarse and final alignment marks. • Coarse and final alignment marks are distinguished in frequency spectrum. • Alignment shows nanoscale precision in hundreds of microns range. Abstract We propose a novel alignment method with nanoscale precision and hundreds of microns detecting range for proximity lithography. With this method, both coarse and final alignments are realized by complex grating based on moiré fringe. For distinguishing the complex gratings in frequency spectrum, there is no interference between the coarse and the final alignment parts. Within only one pattern, modulation of the coarse mark and phase of the final mark can be calculated respectively. Combining the two results, we can do the alignment with nanoscale precision in large measurement range. Furthermore, the structure of our measurement system is simple. Simulation and experiments are carried out to validate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract The recently reported (Alcalá Ochoa, 2018) approximation to the Rayleigh–Sommerfeld diffraction integrals (RSDI) is used to obtain a set of expressions to calculate the diffraction properties of non-rotationally symmetric optical systems illuminated with polarization fields. It is proved that the three two-dimensional integrals of RSDI can be expressed accurately from two to eight one-dimensional integrals depending of the type of polarization studied. It is proved also that previous developments based on Taylor's approximations to the RSDI can be described by these new expressions. [ABSTRACT FROM AUTHOR]

Abstract Asymmetric light transmission components, such as optical diodes, have attracted great interest for the capability of unidirectional light propagation. Highly desirable key performances of above devices are high unidirectionality, wide operational bandwidth and small scale. In this paper, we present an efficient design for asymmetric light transmission components in two-dimensional air-hole photonic crystals based on silicon. Through introducing tapered structure on the heterostructure interface, the forward transmittance of the optimized photonic crystal structure has increased greatly than that of the original structure almost within the entire frequency range (0.18–0.261 c/a). Meanwhile, the peak transmittance for the optimized structure increases by about 68.3%, varying from 28.4% to 47.8%. Moreover, the designed optical devices can effectively function as unidirectional equal-beam splitters, and multiple functions can be achieved synchronously in only one structure, which are important in the complex optical integrated circuits. Highlights • Asymmetric light transmission components based on PC heterointerface optimization are realized in broad bandwidths. • The optimized PC structure can effectively function as unidirectional equal-beam splitters. • Multiple functions can be achieved synchronously in only one PC structure. [ABSTRACT FROM AUTHOR]

A recent literature introduced the stationary, three-dimensional (3D), and electromagnetic (EM) Gaussian-Schell model (GSM) source through the analytic approach. In this paper, investigations are performed on the statistical properties of the degree of polarization (DOP) and state of polarization (SOP) of the far-zone radiated beam from such source. The effects of initial widths and correlation coefficients of the source on the DOPs and SOPs of the radiated beam are numerically analyzed. Furthermore, comparisons are held for the DOPs and polarization ellipse shapes of the radiated beam between the uniformly and non-uniformly polarized sources cases. Our results greatly enrich the current knowledge of 3D, EM sources with arbitrary state of polarization. [ABSTRACT FROM AUTHOR]

In order to study the influence mechanism of conical shock waves on pulsed laser forward detection, an analytical method is proposed for arbitrary Mach number and cone angle conditions. Based on traditional gas dynamics and physical optics, a simplified model of Gaussian beam transmission across the conical shock wave flow field is established. On this basis, combined with the process of pulsed laser detection, the analytical expression of pulsed laser echo waveform under the influence of shock wave is derived. Simulation results show that the conical shock wave under different conditions can lead to beam deflection, focus, and reflection to different degrees. Furthermore, the variation of echo waveform caused by aero-optical effect is also analyzed, and it is shown that the peak power, pulse width and arrival time of echo all fluctuate greatly with rolling motion at different shock angle and cone angle, among which the shift of the arrival time and the reflection effect of shock wave have the largest impact on laser detection. [ABSTRACT FROM AUTHOR]

Abstract We investigate the contribution of four-photon bunching term in fourth-order double-slit interference intensity correlation based on two different detection schemes with a pseudo-thermal light source. It is clearly demonstrated that the resolution of intensity correlation is significantly enhanced by using of double-slit in both fourth-order and third-order intensity correlation. Meanwhile, the visibility of fourth-order correlation can be dramatically improved in contrast to the third-order due to the four-photon bunching term by contributing in the visibility of fourth-order correlation. The position and full width at half maximum of interference peaks of fourth-order intensity correlation are same as third-order. We also use two different scanning approaches to change the resolution and visibility of interference intensity correlation. In the first detection scheme, we scan three reference detectors along the same orientation and speed. In second detection scheme we scan two of three reference detectors in the same orientation, and speed of one reference detector is twice that of the other, and simultaneously moving the other two reference detectors with opposite orientation but identical speed. Those investigations can also be promoted to high order intensity correlation of thermal light. [ABSTRACT FROM AUTHOR]

Abstract Point spread function defines the imaging property of a linear optical imaging system. Here Fermat spiral is introduced into Greek-ladder sieves to generate multiple different point spread functions along light propagation and further to realize multiplanar anisotropic imaging. Theoretical analysis and experimental results show that this kind of diffractive lenses has trifocal spots on the optical axis. The first and third foci are asymmetrical, meaning that they can provide different spatial resolution in different directions. The second focus is a vertex focal spot, which can be used for phase-contrast imaging. Due to amplitude-only diffractive lenses, they will have great potential in X-ray holography, X-ray microscopy, phase-contrast bio-imaging and optical trapping for the next generation of synchrotron radiation and free electron laser in the future. © 2018 Elsevier Ltd. All rights reserved. [ABSTRACT FROM AUTHOR]

Abstract The coherence of cold atom trapped and cooled by the partially coherent light (PCL) is investigated experimentally through Rabi oscillations. We control the degree of the spatial coherence of the laser beams by the modulation of electro-optic crystal. The experimental results show that the cold atoms captured by the different coherent degree of light have little different coherence properties and almost the same capacity of resisting disturbance, which indicates that the coherence of cold atom is affected weakly by the coherence of cooling field. [ABSTRACT FROM AUTHOR]

Abstract Helico-conical beams (HCBs) are a class of orbital angular momentum (OAM)-carrying beams with spiral phase and intensity profiles. In this communication, we demonstrate the use of a common path interferometer (CPI) to phase-image incoming HCBs and directly detect their OAM-associated properties. The output intensity of the CPI is a direct mapping of the HCB's phase, hence both the topological charge value and sign manifest in the output intensity distribution. The topological charge value is calculated by fringe counting, while the helicity is determined by observing the intensity along the φ = 0 region. With our current CPI setup, we can firmly detect up to l = ± 20. Higher values of l lead to a decrease in the fringe visibility, but this can in principle be improved by tailoring the parameters of the phase contrast filter (PCF) employed in the CPI. We present analytical expressions to optimize the CPI for HCB charge detection. [ABSTRACT FROM AUTHOR]

Abstract The conductivity of a monolayer graphene at intraband transitions is sensitive on the Fermi level and on the wavelength of the incident beam. Changing conductivity values through these parameters thus may offer better control of light impinging on graphene. In this paper, we investigate reflection, the simplest interaction of light on such surface, by looking at the Goos-Hänchen (GH) shift experienced by the incident light where the wavelength is at terahertz range. With this wavelength range, we assume that the carriers in graphene undergo intraband transition. We calculate that spatial and angular GH shifts can be present. For both GH shifts in general, we find that increasing the Fermi level changes the incident angle at which the maximum GH shifts arise. Moreover, we see that at higher frequencies, the amount of beam shift decreases with the Fermi level. At lower frequencies on the other hand, the shift becomes proportional to the Fermi level. Upon obtaining the measurable shifts, we find that the magnitude of the physical shifts can be easily detected given appropriate experimental parameters. Our results may increase the utility of graphene in optoelectronics devices and applications. [ABSTRACT FROM AUTHOR]

Abstract A cylindrical parabolic reflector, composed of mesh grid, is modeled by a resistive surface. The analysis of the scattered waves is performed by the physical optics integral, which was developed for resistive surfaces. The integral is evaluated asymptotically for large values of the wave-number in high-frequencies. The geometrical optics and diffracted fields are obtained by the methods of stationary phase and edge point respectively. The uniform forms of the diffracted waves are derived. The total wave and its components are investigated numerically for different values of surface resistivity. [ABSTRACT FROM AUTHOR]

Abstract Aiming at the demand of the detection and recognition of the typical scene and the key condition for the radar, a modeling method for synthetical scene based on the electromagnetic model is proposed. Firstly, based on the target group-varying parameters of the targets, including the position and gesture, and the geometry material modeling of targets by the three-dimensional geometry transform method. More, use the electromagnetic calculation method to acquire the narrow-band and wide-band electromagnetic scattering characteristic of the complex scene, including specular reflection, edge diffraction and multi-reflection from the target group are obtained by Physical Optics (PO), Equivalent Edge Currents (EEC) and Shooting-and-Bouncing Ray (SBR) methods. The simulation example analyses the wide-band swept data and the HRRP course feature, and validates the correctness of the modeling method of complex scene. [ABSTRACT FROM AUTHOR]

Abstract For electrically large targets, the scattering mechanics are specular reflection, edge diffraction, multiple reflection, etc. Multiple reflection scattering mechanics is the mainly contribution for complex targets.Diagnosis of the scattering structure which causes this mechanics is difficult to judge and orientate. In current paper, a hotspot analysis method is proposed according to the laws of physical optics and geometrical optics, which can intuitively show the contribution of different parts to the overall radar cross section (RCS), so as to judge the components which cause the strong scattering sources and to quantitatively describe the scattering mechanic of complex targets. Hotspot analysis has great application in the analysis of target electromagnetic scattering, the design and development of target simulators, and the stealth transformation of targets. [ABSTRACT FROM AUTHOR]

Abstract Azimuthal fractal spiral zone plates (AFSZPs) with particular fractal characteristics are proposed which have the ability to increase the number of foci comparing with conventional spiral zone plates. The generated beams possess sequence of optical vortices along the propagation direction with preset resolution. Numerical simulations are carried out under plane wave illumination and the good performance of this fractal diffractive optical elements are verified experimentally based on a programmable phase-only liquid-crystal spatial light modulator (SLM). In addition, the effects on the axial irradiance and resolution of foci caused by variations of parameters are also presented. [ABSTRACT FROM AUTHOR]

Abstract Dynamic patterns have been studied theoretically and experimentally in this work. The microstructure consists of a base layer made up of micropattern array, and a superposed revealing layer made up of microlens array. Dynamic patterns will be observed directly on the revealing layer without visual facilities. When the viewing angle changes, displacement of dynamic patterns is produced. This technology is compared with traditional moiré techniques. In addition, analytical models to describe its structures are derived based on a vector method. There is a good agreement between the theoretical and experimental results, which indicates this study is helpful to design various kinds of dynamic patterns and dynamic effects, and this technology can be applied for many applications, especially in anti-counterfeiting field. [ABSTRACT FROM AUTHOR]

Superposition theory of spiral harmonics is employed to examine the transmission of turbulence-induced orbital angular momentum (OAM) modes on non-vortex Gaussian–Schell model (GSM) beam in weak to strong atmospheric turbulence. Turbulent aberrations clearly create various OAM modes on GSM beams propagation in the atmosphere, which can be mitigated by applying a wave-front aberration correction method. The effect of wave-front correction method is clearly enhanced by increasing the diameter of circular sampling aperture. As the turbulence strength enhances, low-order OAM modes appear firstly, followed by high-order ones. The probability of turbulence-induced OAM mode decreases, and the peak position of OAM mode probability density deviates from the beam center, as the topological charge increases. Atmospheric turbulence effects degrade the coherence of laser beams when they propagate in the atmosphere. The phase of a laser beam with worse coherence or larger spot size is more sensitive to atmospheric turbulence. [ABSTRACT FROM AUTHOR]

The methods of physical optics and physical theory of diffraction are reviewed for electromagnetic waves. The Fermat principle and its’ modified version are investigated and the necessity of the introduction of a variable unit vector is put forth. The scattering integrals of modified theory of physical optics are reviewed in this context. Recent comments on the modified theory of physical optics are discussed and refuted clearly. A proof is given on the nature of the physical theory of diffraction’s correction terms. The proof is visualized with some numerical simulations. [ABSTRACT FROM AUTHOR]

Three different mathematical solutions of a physical optics model for far field diffraction by an aperture due to Karczewski and Wolf are discussed. Only one of them properly describes diffraction by an aperture and can, by applying Babinet's principle, be used to model diffraction by the corresponding plane obstacle, and by further approximation , diffraction by a particle . Studying absorbing scatterers allows a closer investigation of the external diffraction component because transmission is negligible. The physical optics model has been improved on two aspects: (i) To apply the diffraction model based on two-dimensional apertures more accurately to three-dimensional objects, a size parameter dependent volume obliquity factor is introduced, thus reducing the slightly overestimated side scattering computed for three-dimensional objects. (ii) To compensate simplifications in the underlying physical optics diffraction model for two-dimensional apertures [26] a size parameter dependent cross polarisation factor is implemented. It improves cross polarisation for diffraction and reflection by small particle facets. 2D patterns of P 11 , –P 12 /P 11 and P 22 /P 11 and their azimuthal averages for slightly rough absorbing hexagonal prisms in fixed orientation are obtained and compared with results from the discrete dipole approximation. For particle orientations where shadowing is not negligible, improved phase functions are obtained by using a new method where the incident beam is divided into sub-beams with small triangular cross sections. The intersection points of the three sub-beam edges with the prism define the vertices of a triangle, which is treated by the beam tracer as an incidence-facing facet. This ensures that incident facing but shadowed crystal facets or regions thereof do not contribute to the phase functions. The method captures much of the fine detail contained in 2D scattering patterns obtained with DDA. This is important as speckle can be used for characterizing the size and roughness of small particles such as ice crystals. [ABSTRACT FROM AUTHOR]

We present a transparent conductor composed of the flower-shaped multi-angle metal ring clusters (FMMRC) interface structure for simultaneous highly optical transparency with uniform light transmission and microwave shielding performance both theoretically and experimentally. The measured normalized optical transmittance of the FMMRC sample is ~95% covering the visible to near infrared spectra with a sheet resistance of ~5.6 Ω/sq., offering favorable conductivity as a transparent electromagnetic interference (EMI) shielding component. Particularly, the FMMRC structure shows a uniform light transmission with a homogeneous high-order diffraction distribution which introduces negligible impact on optical imaging and observation. In the meantime, both simulations and experimental results demonstrate the shielding effectiveness of the FMMRC structure is >21 dB from 12 to 18 GHz, obtaining an excellent shielding performance for a single-layer metal structure with high optical transmittance. The proposed FMMRC is insensitive to the polarization direction due to the symmetrical arrangement. These excellent properties of the FMMRC structure represents the highest figure of merit single-layer metallic mesh ever reported, showing great potential in transparent EMI devices as well as transparent electrodes. [ABSTRACT FROM AUTHOR]

The radial-to-axial polarization transformation that accompanies the focusing of a cylindrically symmetric vector beam by a thin lens is analyzed by use of polarization ray tracing and wave optics. A simple expression for the axial electric field at focus is derived in terms of an integral of the incident radial electric field over the entrance pupil of the lens. Subsequently, from Maxwell’s equations, the near-axis radial electric field and azimuthal magnetic field in the focal plane are determined. Finally, the concept of wave impedance is invoked to obtain the electric field on-axis near focus. [ABSTRACT FROM AUTHOR]

Modified theory of physical optics (MTPO) solution for a soft/hard strip is analyzed. It is shown that this solution is incorrect because the MTPO Green function does not satisfy boundary conditions. Defects of MTPO in calculations of fringe waves are also noticed. [ABSTRACT FROM AUTHOR]

Agaricus blazei Murill is an edible and medicinal mushroom favored in many countries, by virtue of both its delicious taste and its potential health benefits such as its purported anticancer activity. A neutral α-glucan (ABM40-1) with a carbohydrate content of 96% was purified from the high-speed shearing homogenization extracts of A . Blazei Murill by ethanol precipitation and column chromatography. Methylation analysis along with nuclear magnetic resonance spectroscopy revealed that ABM40-1 was an α-(1 → 4)- d -glucopyranan with O -6 position occasionally occupied with α-Glc p -(1 → or α-Glc p -(1 → 6)-β-Glc p -(1 → side chains. A weight-average molecular weight of 7.34 × 10 6 Da was determined for ABM40-1 and its chain in solution was revealed as a compact sphere by size exclusion chromatography (SEC) coupled with a laser light scattering. This spherical conformation was also further confirmed by Congo red test and using atom force microscopy. These results suggest it would be worthwhile to further study the potential bioactivities of ABM40-1. [ABSTRACT FROM AUTHOR]

The diffracted fields by resistive and conductive half-screens, which transmit a portion of the incident wave and reflect the remaining part, are expressed in terms of simple expressions that are based on the diffraction coefficient of an impedance half-plane. Also alternative representations are derived for the diffracted fields and their effects are studied for different values of surface parameters. The results are examined numerically. [ABSTRACT FROM AUTHOR]

The scattering problem of waves by a strip, the faces of which are composed of soft and hard surfaces, is investigated by the method of modified theory of physical optics. The scattering integral is divided into two parts according to the single effects of the faces. The boundary conditions are integrated into the integrals and the resultant field expressions are obtained by the asymptotic evaluation methods. The scattered waves are examined numerically. [ABSTRACT FROM AUTHOR]

The bulk single-scattering properties of various randomly oriented aggregate ice crystal models are compared and contrasted at a number of frequencies between 89 and 874 GHz. The model ice particles consist of the ten-branched plate aggregate, five-branched plate aggregate, eight-branched hexagonal aggregate, Voronoi ice aggregate, six-branched hollow bullet rosette, hexagonal column of aspect ratio unity, and the ten-branched hexagonal aggregate. The bulk single-scattering properties of the latter two ice particle models have been calculated using the light scattering methods described in Part I, which represent the two most extreme members of an ensemble model of cirrus ice crystals. In Part I, it was shown that the method of physical optics could be combined with the T-matrix at a size parameter of about 18 to compute the bulk integral ice optical properties and the phase function in the microwave to sufficient accuracy to be of practical value. Here, the bulk single-scattering properties predicted by the two ensemble model members and the Voronoi model are shown to generally bound those of all other models at frequencies between 89 and 874 GHz, thus representing a three-component model of ice cloud that can be generally applied to the microwave, rather than using many differing ice particle models. Moreover, the Voronoi model and hollow bullet rosette scatter similarly to each other in the microwave. Furthermore, from the various comparisons, the importance of assumed shapes of the particle size distribution as well as cm-sized ice aggregates is demonstrated. [ABSTRACT FROM AUTHOR]

This review paper presents the achievements and present developments in lossy mode resonances-based optical fiber sensors in different sensing field, such as physical, chemical and biological, and briefly look forward to its future development trend in the eyes of the author. Lossy mode resonances (LMR) is a relatively new physical optics phenomenon put forward in recent years. Fiber sensors utilizing LMR offered a new way to improve the sensing capability. LMR fiber sensors have diverse structures such as D-shaped, cladding-off, fiber tip, U-shaped and tapered fiber structures. Major applications of LMR sensors include refraction sensors and biosensors. LMR-based fiber sensors have attracted considerable research and development interest, because of their distinct advantages such as high sensitivity and label-free measurement. This kind of sensor is also of academic interest and many novel and great ideas are continuously developed. [ABSTRACT FROM AUTHOR]

We present a wave-mixing induced transparency that can lead to a hyper-Raman gain-clamping effect. This new type of transparency is originated from a dynamic gain cancellation effect in a multiphoton process where a highly efficient light field of new frequency is generated and amplified. We further show that this novel dynamic gain cancellation effect not only makes the medium transparent to a probe light field at appropriate frequency but also eliminates the probe field propagation phase shift. This gain-cancellation-based induced transparency holds for many potential applications on optical communication and may lead to effective suppression of parasitic Raman/hyper-Raman noise field generated in high intensity optical fiber transmissions. [ABSTRACT FROM AUTHOR]

In this paper, propagation dynamics of off-axis symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams have been explored numerically based on rigorous scalar diffraction theory. The distribution properties of phase and intensity play an important role in driving the propagation dynamics of OVs. Numerical results show that the single off-axis vortex moves in a straight line. The displacement of the single off-axis vortex becomes smaller, when either the order of flatness N and the beam size ω 0 are increased or the off-axis displacement d is decreased. In addition, the phase singularities of high order vortex beams can be split after propagating a certain distance. It is also demonstrated that the movement of OVs are closely related with the spatial symmetrical or asymmetrical distribution of vortex singularities field. Multiple symmetrical and asymmetrical optical vortices(OVs) embedded in flat-topped beams can interact and rotate. The investment of the propagation dynamics of OVs may have many applications in optical micro-manipulation and optical tweezers. [ABSTRACT FROM AUTHOR]

We report on observation of well-pronounced characteristic features of elastic light scattering of evaporating solution and suspension microdroplet of the anionic surfactant sodium dodecyl sulfate (SDS) and colloidal silica (SiO 2 ) nanospheres in diethylene glycol (DEG) during SDS surface layer and structure formation (crystallization). For pure DEG/SDS solution droplet evaporation process, characteristic evaporation transitions manifested in the evolution of the droplet radius, a ( t ) for all the SDS concentrations (C = 20  mM, 40  mM and 100  mM) studied as well as well-pronounced intensity signals characterizing SDS soft gel-solid transitions for initial SDS concentrations, C  >  40  mM. In the case of microdroplets composed of DEG/SDS with controlled addition of colloidal silica, the intensity fluctuations were enhanced and had profiles dependent on the initial composition of the suspension. Exemplary wet droplets at the initial evaporation stages and final dry aggregates of SDS and SDS/SiO 2 were deposited on a substrate and observed with Scanning Electron Microscopy (SEM). Features of the deposited structures correlate well with the elastic scattered light measurements characterizing the drying processes. [ABSTRACT FROM AUTHOR]

Good-optical-quality single crystals of Semicarbazide Picrate (SP), a new organic charge transfer molecular complex salt, were successfully synthesized and grown by the slow evaporation solution growth technique. The grown crystal is analyzed by various instrumentation techniques. The structure of the grown crystal as determined by single crystal XRD diffraction analysis. The presence of functional groups in the SP crystals is confirmed by FT-IR vibrational analysis. The optical transparency has been studied using UV–vis spectrophotometer. The relative second harmonic generation (SHG) efficiency measurements reveal that the SP crystals is a efficient nonlinear optical (NLO) material having an activity 1.4 times as that of the reference material potassium dihydrogen phosphate. The TG/DTA thermal analyses reveal the purity of the sample and no decomposition is observed up to the melting point. The mechanical properties of the crystal are examined by Vicker's microhardness test. The dielectric permittivity, dielectric loss and AC conductivity of the crystal are measured at various temperatures. [ABSTRACT FROM AUTHOR]

Linear polarizers are commonly used for projecting the direction of the electric field of a transverse paraxial beam on the direction of the polarizer axis. However, the use of these devices with highly convergent field poses a practical problem because the non transversal character of electric field. In this article, we discuss the behavior of highly focused beams with spiral polarization when they pass through a polarizer. Interestingly, beams with azimuthal polarization display a non negligible irradiance in the direction of propagation after passing through a polarizer. On top of that, we found that the irradiance of a highly focused radially polarized beam after a polarizer is notably different from the projection of the field on the direction of the polarizer axis. [ABSTRACT FROM AUTHOR]

We demonstrated a timing fluctuation suppression in outdoor laser-based atmospheric radio-frequency transfer over a 110 m one-way free-space link using an electronic phase compensation technique. Timing fluctuations and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process. With transferring a 1 GHz microwave signal over a timing fluctuation suppressed transmission link, the total root-mean-square (rms) timing fluctuation was measured to be 920 femtoseconds in 5000 s, with fractional frequency instability on the order of 1 × 1 0 − 12 at 1 s, and order of 2 × 1 0 − 16 at 1000 s. This atmospheric frequency transfer scheme with the timing fluctuation suppression technique can be used to fast build an atomic clock-based frequency free-space transmission link since its stability is superior to a commercial Cs and Rb clock. [ABSTRACT FROM AUTHOR]

Facets shadowing test is time-consuming and inefficient in calculation of radar cross section utilizing physical optics (PO). A novel method is proposed in this paper by covering the target by overlapped spheres which divide the facets to several consistent groups. In order to ensure that every facet is included by at least one sphere, the adjacent spheres must have a common area and some facets may be included by more than one sphere. Spheres’ shadowing tests are conducted before the facets’ tests. If one sphere does not shadow the facet under testing, then the facet cannot be shadowed by any facet within the sphere. Otherwise, every facet within the sphere should be judged whether to shadow the facet. Numerical simulation is conducted to validate the efficiency and accuracy of the algorithm. The spheres’ size on performance of the algorithm is also discussed in this paper and an optional choice of the parameter is achieved resulting 89% time saving. [ABSTRACT FROM AUTHOR]

The polarization-dependent reflection properties of single-layer antireflection coatings (ARCs) on transparent substrates at oblique-incidence are examined in detail. This includes the intensity reflectances | R p | 2 and | R s | 2 for incident p - and s -polarized light as functions of angle of incidence φ and substrate refractive index n 2 . For unpolarized or circularly polarized light incident at φ = 45°, we find that the average reflectance is < 2.5% for all values of n 2 < 10. The reflectance difference R D = | R s | 2 − | R p | 2 exhibits a maximum near φ = 80°, whose magnitude and exact location are functions of n 2 . At φ = 45°, the RD is a function of n 2 that has its own peak of 0.009 at n 2 ≈ 2.0. A non-trivial differential reflection phase shift Δ = δ p − δ s near-normal incidence ( φ = 0.1°) is calculated as a function of n 2 . Finally, the principal angle, principal azimuth, and second Brewster angle that are usually defined for bare absorbing substrates, are determined for single-layer ARCs on transparent substrates as functions of n 2 . [ABSTRACT FROM AUTHOR]

Recently, it was discovered that excitation of the oriented model benzene from its aromatic electronic ground state S 0 ( 1 A 1 g ) to the non-aromatic S 0 + S 2 ( 1 B 1 u ) superposition state generates negative and positive partial charges on alternating carbon atoms. Subsequently, they vary periodically, due to adiabatic attosecond charge migration AACM. Here, we determine the angular electronic flux that mediates this new type of AACM, by means of quantum dynamics simulations. It is found to be periodic, with period τ ¯ = 590 as , and with a pincer motion type pattern such that a total of 1.2 valence electrons flow concertedly between alternating sources and sinks at the carbon nuclei. [ABSTRACT FROM AUTHOR]