Ellipticity Angle Research Articles

Lessons from a blind study of simulated lenses: image reconstructions do not always reproduce true convergence

ABSTRACT In the coming years, strong gravitational lens discoveries are expected to increase in frequency by two orders of magnitude. Lens-modelling techniques are being developed to prepare for the coming massive influx of new lens data, and blind tests of lens reconstruction with simulated data are needed for validation. In this paper, we present a systematic blind study of a sample of 15 simulated strong gravitational lenses from the EAGLE suite of hydrodynamic simulations. We model these lenses with a free-form technique and evaluate reconstructed mass distributions using criteria based on shape, orientation, and lensed image reconstruction. Especially useful is a lensing analogue of the Roche potential in binary star systems, which we call the lensing Roche potential. This we introduce in order to factor out the well-known problem of steepness or mass-sheet degeneracy. Einstein radii are on average well recovered with a relative error of ${\sim }5{{\ \rm per\ cent}}$ for quads and ${\sim }25{{\ \rm per\ cent}}$ for doubles; the position angle of ellipticity is on average also reproduced well up to ±10°, but the reconstructed mass maps tend to be too round and too shallow. It is also easy to reproduce the lensed images, but optimizing on this criterion does not guarantee better reconstruction of the mass distribution.

High-throughput fabrication of polymethylmethacrylate nano-hole arrays for structural coloration using proton beam writing made diamond stamp

We demonstrate the fabrication of a diamond stamp through proton beam writing (PBW) coupled with reactive ion etching (RIE), and the process of corresponding thermal nano-imprinting to free-standing polymethylmethacrylate (PMMA) film. Strong structural coloration from the imprinted nano-hole based PMMA patterns was observed. Additionally, we see that 8 nm Cr coating can enhance the structural coloration intensity of PMMA nano-hole. Furthermore, a series of Maxwell solver based finite-difference time-domain (FDTD) simulations were performed to find out theoretical explanations to what we observed in the experiments. The simulation results are in a good agreement with the experimental observations in terms of structural color, color intensity contrast, and Cr coating enhancement. The dependence between the scattering cross section of elliptic nano-hole and polarization angle is discussed as well. This study provides an insight into rapid and high-throughput fabrication of polymer based structural coloration, thus paving the way to bring structural color printings into commercialization driven by large-scale industrial production.

Formation of an optical field with regular singular-skeleton structure by the double-phase-ramp converter

We study the system of phase singularities (‘singular skeleton’) formed when a quasi-plane wave (QPW) input beam diffracts at a double-phase-ramp (DPR) converter. The external (OV positions and 3D trajectories) and internal (ellipticity and orientation angle of the equal-intensity ellipses in the OV-core area) singular-skeleton features are investigated both theoretically and in experiments. The results are presented in comparison with the singular skeleton formed by the DPR when the incident beam is Gaussian. In contrast to the limited number of OVs in the synthesized OV chain, divergent 3D OV trajectories and variable OV morphologies depending on their off-axis distances, which is typical for the Gaussian input beam, it is shown that the QPW-generated diffracted beam carries a rectilinear chain of equidistant optical vortices (OV) with identical morphology parameters. Such singular-skeleton configurations can be useful for the applications to metrology and micromanipulation, in particular, for the multi-particle optical trapping and guiding.

A Comparison of Supermassive Black Hole Mass of NGC 4151 Using Different Methods

We found a new value of supermassive black hole (SMBH) mass in the middle of type 1 Seyfert, NGC 4151 galaxy. In this Study, the image of NGC 4151 galaxy was deprojected to face-on, using spiral galaxy of face-on, and applied IRAF to calculate the ellipticity and position angle of major-axis. A two-dimensional (2D) Fast Fourier Transform (FFT) applied to the deprojected image to calculate the spiral arm of NGC 4151 galaxy, and, in that way, find a central mass AGN 4151 galaxy. We compared our results of the mass of SMBH in in the center of NGC 4151 galaxy with the mass of SMBH calculated using different methods ((direct method: stellar dynamics, gas dynamics, reverberation mapping), and indirect method: MBH-σ*, MBH-Vrot, MBH-n, MBH-Lbulge, and MBH-P correlations). We concluded that the results of mass for these methods are in agreement with the estimated ones, i.e. using direct methods.

Carbon Nanotubes-Based Magneto-Optically Tunable Structure for Terahertz Wave Polarization Control-=SUP=-*-=/SUP=-

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a randomly oriented single-walled carbon nanotube (SWCNT) thin film on a high resistivity monocrystalline silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping and an external static magnetic field. Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the electromagnetic waves transmitted through the Si substrate and the SWCNT on the Si substrate were obtained experimentally based on the system of the Stokes parameters. The results of the study of this magneto-optically tunable structure confirm the fact that, based on the Faraday effect in the SWCNT, it is possible to devise efficient tunable THz polarization modulators for use in physics, chemistry, medicine, and the latest security and telecommunication systems.

Variability of Circular Depolarization Ratio in Radar Sensing of the Medium Filled with Hydrometeors

Circularly polarized waves are most sensitive to the influence of the propagation medium factors such as differential phase shift and differential attenuation. The reason of that is a feature of the wave polarization transformation. Such circumstances require consideration during designing radars working with circularly polarized waves. The aim of the study is to develop of approach for estimating the effect of the wave polarization transformation on a value of one of the most informative parameters based on the use of Jones vector component functional dependence on a polarization ellipse orientation angle and ellipticity angle. The task of this work is obtaining the analytical equation for the determination of that polarimetric radar informative parameter. As a result, the solution for the case of wave backscatter by the propagation medium was obtained when the medium basis orientation differs from the radar basis orientation. The estimation of the circular depolarization ratio providing the determination of regions with its raised value was obtained

Exact Solutions for the Local Parameters of Polarization Modes in Coiled Optical Spun Fibers with Strong Unperturbed Linear Birefringence. I. Nonresonant Linear Transformation

The propagation of monochromatic radiation in coiled spun optical fibers is considered. The local parameters of the elliptical polarization eigenmodes, elliptic birefringence, and the ellipticity angle are the sum of the constant and variable components, with the latter being measured almost according to the harmonic law depending on the length of the fiber. The magnitudes of the constant components are significantly higher than the amplitudes of the variable components. The dependence of the local azimuth of the major axis of the ellipse of the polarization eigenmodes increases almost linearly.

Polarization properties of single-walled carbon nanotube thin film on silicon substrate in terahertz frequency range

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a randomly oriented single-walled carbon nanotube (SWCNT) thin film on a silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping (OP) and an external static magnetic field (MF). Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the Si substrate and the SWCNT thin film on the Si substrate were obtained experimentally. The results confirm the fact that, based on carbon nanotubes, it is possible to devise efficient tunable THz polarization modulators for use in the latest security and telecommunication systems.

Polarization properties of few-layer graphene on silicon substrate in terahertz frequency range

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study polarization properties of a few-layer graphene (FLG) on a silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping and an external static magnetic field. Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the electromagnetic waves transmitted through the Si substrate and the FLG on the Si substrate were obtained experimentally and theoretically. The results confirm the fact that, based on the FLG, it is possible to devise efficient tunable THz polarization modulators for use in the latest security and telecommunication systems.

Lattice Collective Interaction Engineered Optical Activity in Metamaterials

AbstractThe metamaterials with chiral metamolecular structure designs would show optical activity. In the past, researchers devoted themselves to proper designs of the individual metamolecules to improve the optical activity performance, however the roles of the lattice collective modes in the metamaterial array to the final optical activity have received much less attention. Here, how collective resonances can be utilized to engineer the optical activity of the metamaterials is systematically studied. Metamaterial arrays consisting of various numbers of “L”‐shaped chiral metamolecules are fabricated. It is illustrated that the intermolecule collective interactions are capable to dramatically improve the quality factor of the resonances of metamolecule ensembles. Also, it is shown that with the aid of lattice collective resonances, the spectral linewidth of the optical rotation and ellipticity angle modification to the light collapse efficiently and the magnitudes of the optical activity effects can be dramatically boosted. Both the spectral line collapses and the optical activity magnitude becomes saturated as the size of metamaterial array becomes larger than certain sizes, which implies the maximum coupling length between the metamolecules. The results provide a new freedom in optimizing the optical activity of the chiral metamaterials.

Turbulence-induced changes in the state of polarization of partially polarized, partially coherent pulsed electromagnetic beams propagating through anisotropic turbulence

The changes in the state of polarization of partially polarized, partially coherent pulsed electromagnetic beams propagating along a horizontal path through anisotropic turbulence are investigated. Unpolarized and partially polarized, partially coherent pulsed electromagnetic Gaussian Schell-model beams are compared in terms of the turbulence-induced changes in the spectral degree of polarization. Our analysis is focused on models pertaining to electromagnetic Gaussian Schell-model pulsed beams but can either be readily reduced to scalar or be readily generalized to other beam classes. Within the framework of the anisotropic generalized exponential spectrum, considering simultaneously the finite inner and outer scales of turbulence and the asymmetric property of turbulence eddies in the orthogonal x y -plane throughout the propagation path, we derive analytical expressions for the cross-spectral density matrix, spectral degree of polarization, orientation angle, and degree of ellipticity. Finally, we study the effects of the anisotropic turbulence parameter on the spectral degree of polarization, orientation angle, and degree of ellipticity of the beams. Our results can be useful for applications involving partially polarized, partially coherent pulsed beams propagating through atmospheric turbulence.

Polarization evolution dynamics of dissipative soliton fiber lasers

Dissipative solitons emerge as stable pulse solutions of nonintegrable and nonconservative nonlinear physical systems, owing to a balance of nonlinearity, dispersion, and loss/gain. A considerable research effort has been dedicated to characterizing amplitude and phase evolutions in the spatiotemporal dynamics of dissipative solitons emerging from fiber lasers. Yet, the picture of the buildup process of dissipative solitons in fiber lasers is incomplete in the absence of corresponding information about the polarization evolution. Here, we characterize probabilistic polarization distributions in the buildup of dissipative solitons in a net-normal dispersion fiber laser system, mode-locked by single-wall carbon nanotubes. The output optical spectra under different pump powers are filtered by a tunable filter, and are detected by a polarization state analyzer. The laser system operates from random amplified spontaneous emission into a stable dissipative soliton state as the cavity gain is progressively increased. Correspondingly, the state of polarization of each spectral wavelength converges towards a fixed point. To reveal the invariant polarization relationship among the various wavelength components of the laser output field, the phase diagram of the ellipticity angle and the spherical orientation angle is introduced. We find that, within the central spectral region of the dissipative soliton, the state of polarization evolves with frequency by tracing a uniform arc on the Poincare sphere, whereas in the edges of the dissipative soliton spectrum, the state of polarization abruptly changes its path. Increasing cavity gain leads to spectral broadening, accompanied by a random scattering of the state of polarization of newly generated frequencies. Further increases of pump power result in dissipative soliton explosions, accompanied by the emergence of a new type of optical polarization rogue waves. These experimental results provide a deeper insight into the transient dynamics of dissipative soliton fiber lasers.

Roll-Invariant Target Parameter Extraction From POLSAR Data

In this article, we develop two target parameters to model the interaction between a target and a polarization wave. The two parameters are the target ellipticity angle (TEA) and the target phase angle (TPA). The concept of reflection symmetry or rotation symmetry is used to explain the robustness of the estimation method and to show problems associated with other algorithms. C-band Radarsat-2 and L band ALOS PALSAR multi-look full polarimetric images are used to substantiate the parameters, and validate the effectiveness of them. In addition, the TEA and TPA are compared with $\alpha - \beta $ model and Touzi TVSM model for single-look polarimetric SAR data. Experimental results show that the two target parameters are beneficial supplements for interpreting the target scattering processes and separating buildings from other targets.

Polarization Responses of a Solitary and Optically Injected Vertical Cavity Spin Laser

The polarisation properties of a quantum well spin – vertical cavity surface emitting laser (spin – VCSEL), both without injection and with variable polarisation optical injection, are investigated experimentally and compared with the spin flip model (SFM). Without injection, we demonstrate two distinct types of VCSEL-pump response depending on the signs of the linewidth enhancement factor, birefringence and dichroism: firstly where the pump and VCSEL have the same sign of the ellipticity, and secondly where the VCSEL ellipticity, accompanied by the linear polarisation, switches sign. We show that by controlling the injected power, ellipticity or linear angle, near circular polarisation can be obtained. These responses both give insight into the electro-optical injected spin-VCSEL system, and have practical implications for the use of spin VCSELs in unique applications exploiting the ellipticity degree of freedom.

Implementation of Generalized Regression Neural Network Prediction Tool for Evaluating Thermal Performance in a Heat Exchanger by using Triple Elliptical Leaf Angle Strips with Same Orientation and Same Direction

Implementation of Generalized Regression Neural Network Prediction Tool for Evaluating Thermal Performance in a Heat Exchanger by using Triple Elliptical Leaf Angle Strips with Same Orientation and Same Direction

Execution of a Modern Prediction Tool for Evaluation of Thermal Performance in a Heat Exchanger by Expending Triple Elliptical Leaf Angle Strips with Altered Orientation and Opposite Direction

Heat exchangers are the basic devices which are used in many areas wherever applications of heat flow occurs. Its usage varies from common domestic devices to mighty industrial applications. The performance of the heat exchanger plays a very important role for its utilization in many aspects. This performance is not dependent on the design parameters in a particular relationship hence experimental values for thermal performance are taken by utilizing three elliptical leaf strips in a tube and pipe heat exchanger. The three elliptical leaves used in experiment has major to minor axes ratios as 2:1 and distance of 50 mm between two leaves are arranged at different angular orientations from 00 to 1800 with 100 intervals. The leaves are placed in the tube side with different orientation and opposite direction of flow and experimentation is conducted to obtain the values. Based on these datasets available a statistical tool is utilized known as GRNN for the comparison between these obtained experimental values & GRNN values. From this comparison the percentage of error between the values is identified as results.

Using a Generalized Regression Neural Network Prediction Tool to Estimate Thermal Performance in A Heat Exchanger By using Triple Elliptical Leaf Angle Strips with Opposite Orientation and Same Direction

In our day to day hectic schedule humans have got so adaptive to technology that tremendous pressure is built on researchers to produce better equipment with greater output & easier way of human usage. One among these is Heat exchanger which is a device for trading heat and providing comfortable environment either for humans or the equipment .This paper aims at finding a solution in improvement of the thermal performance of the heat exchanger by implementing a statistical tool derived from Artificial Neural Network. The name of the tool is GRNN. (Generalized Regression Neural Network) From a sparse data of inputs (Temperatures, Angle orientation & mass flow rates) the outputs of (outlet temperatures & drop in pressure) are found out using this tool. An experiment is also conducted to find the heat transfer rates and pressure drops. To enhance the heat transfer rate three elliptical shaped leaf strips are introduced in the tube with opposite orientation and same direction. The results obtained from both the sources are compared and the percentage of error is calculated.

Numerical Study of Savonius Wind Turbine Rotor with Elliptic Angle Shape Variation

The Savonius wind turbine uses a half-cylinder blade which is often called a bucket assembled so that the cross-section forms an S. This turbine is seen in the form of a half-cylinder consisting of a concave side and a convex side. This turbine is one type of Vertical Axis Wind Turbine (VAWT) that uses the difference in drag forces between the two buckets to be able to rotate the rotor. Therefore this rotor has the ability to self-start, which other wind turbines do not have, even so, the performance of the turbine. Savonius wind is still relatively low, so that it cannot be applied until now. Many studies have been carried out to improve performance, some of which include adding shielding, end plates, changing the shape of the blades, gap overlap, and others. The analysis in this numerical study included a comparison of the performance of conventional Savonius wind turbines and elliptic Savonius wind turbines with an assumed steady flow 2D flow and using turbulent viscous transitions k-kL-ω and k-ω SST with variations in flow velocity and angle of incidence of flow to the position of the rotor of the Savonius turbine. This results evaluated were the static torque coefficient with respect to the rotor position, the pressure distribution along the blade surface, and the wind flow characteristics near the rotor. The results of this study indicated that the modified wind turbine rotor had a higher static torque coefficient at low speeds. The two types of turbine rotors had relatively the same self-starting capability at high speeds.

Controlling polarization of high-order harmonic generation by molecular alignment in a bicircular laser field

The polarization of high-order harmonic generation in ${\mathrm{H}}_{2}{}^{+}$ driven by a counterrotating bichromatic $\ensuremath{\omega}/3\ensuremath{\omega}$ circularly polarized laser field is investigated theoretically. The elliptically polarized harmonics are characterized by ellipticity and rotation angle, where the latter is expanded to $[\ensuremath{-}\ensuremath{\pi}/2,\ensuremath{\pi}/2]$ by an optimized definition. We find a critical alignment angle where the ellipticity of high-energy harmonics is almost the same, so an attosecond pulse train with a high degree of polarization can be synthesized. In addition, we find that the rotation angle is always different from the alignment angle by ${90}^{\ensuremath{\circ}}$ with a small deflection. Thus, we propose a scheme to control the harmonic polarization state by the molecular alignment angle.

Implementation of GRNN for Evaluating the Pressure Drop and Heat Transfer in a Heat Exchanger By Utilizing Triple Elliptical Leaf Angle Strips With Same Orientation and Opposite Direction

Heat exchangers are the basic devices which are used in many areas wherever applications of heat flow occurs. Its usage varies from common domestic devices to mighty industrial applications. The performance of the heat exchanger shows a very important role for its utilization in many aspects. This performance is not dependent on the design parameters in a particular relationship hence experimental values for thermal performance are taken by utilizing three elliptical leaf strips in a tube and pipe heat exchanger. The three elliptical leaves used in experiment has major to minor axes ratios as 2:1 and distance of 50 mm between two leaves are arranged at different angular orientations from 00 to 1800 with 100 intervals. The leaves are placed in the tube side with same orientation and opposite direction of flow and experimentation is conducted to obtain the values. Based on these datasets available a statistical tool is utilized known as GRNN for the comparison between these obtained experimental values & GRNN values. From this comparison the percentage of error between the values is identified as result.