Stokes Parameters Research Articles

Elliptical Polarization of Localized States in an Anisotropic Single GaAs Quantum Ring

Localized states in an anisotropic single GaAs quantum ring were investigated in terms of polarization dependence of micro-photoluminescence spectrum at 5K. Given four Stokes parameters measured with a pair of linear polarizers and waveplates, the elliptical polarization states of two different vertical confinement states (k=1 and k=2) were compared with phase, rotation, and ellipticity angles. While the polarized emission intensity of the k=2 states becomes enhanced along [1,1,0] compared to that along [1,1¯,0], the polarization asymmetry of the k=1 states shows the opposite result. We conclude the polarization state is determined by the shape of the lateral wavefunctions. In the k=2 state, crescent-like wavefunctions are strongly localized, but the k=1 state consists of two crescent-like wavefunctions, which are connected weakly through quantum tunneling.

Tuning of the Stokes scintillations by controlling the longitudinal coherence

Various imaging techniques such as optical coherence tomography (OCT) and ghost imaging focus on increasing the resolution of the system to enhance the imaging quality. The information of polarization fluctuations of the field can reveal the fine details of the source or object through Stokes correlations. In this study, we provide a framework for the correlation in the fluctuations of Stokes parameters in the longitudinal direction for the general non-collimated fields. We first derive the four scintillation coefficients for a scheme using Gaussian statistics, which are basically the variance of the Stokes parameters. The influence of longitudinal spatial coherence (LSC) and temporal coherence on tuning the scintillation coefficients can be useful in purposely managing the noise of a Stokes parameter. Experimental demonstration of the modulation of the scintillation coefficients owing to frequency and angular spectrum endorse the theoretical findings. The temporal dependence of the Stokes correlations is used to trace the evolution of the polarization of the system. Ghost imaging exploiting the LSC for better resolution can be benefited from the dependence of Stokes scintillation on the angular spectrum width. Moreover, encoding based on dynamical polarization fluctuations can utilize the knowledge of Stokes correlations.

Autocorrelation functions and power spectral densities of the Stokes parameters in a polarization speckle pattern.

The concept of ensemble-average polarization and coherence has been applied to studying fluctuating Stokes parameters in a polarization speckle observed when coherent light is passed through a birefringent polarization scrambler. With the aid of the ensemble-average van Cittert-Zernike theorem for the propagation of ensemble-average polar-coherence, we invesitgate the autocorrelation functions and power spectra of the Stokes parameters to expose the dependence of the polarization-related scale-size distributions on the optical geometries in which the polarization speckle arises. A generalized concept of the Stokes ensemble-average coherence areas is introduced to deal with the polarization-related average areas associated with polarization speckle.

Giant longitudinal spin Hall effect for elliptically polarized light under surface plasmon resonance

We propose a novel and simple method for obtaining the giant longitudinal spin Hall effect (SHE) of the reflected light beam when the elliptically polarized light (instead of the linearly polarized light) at the telecommunication wavelength is obliquely incident on a prism–sodium interface excited by surface plasmon resonance. By introducing the spatially averaged Stokes parameter for a non-uniformly polarized reflected light field, understanding the generation mechanism of the giant longitudinal SHE from a new perspective is realized. The giant longitudinal SHE under the elliptically polarized light reaches 60.28 μm by the optimal parameter setup, and the spin splitting direction of the SHE can be switched by adjusting the amplitude ratio angle and phase difference of the incident elliptically polarized light. These findings open the way for the precise measurement of the ellipticity of the elliptically polarized light and the design of novel fiber-optic devices.

Optical monitoring of the plant growth status using polarimetry

Polarimetry is a powerful characterization technique that uses a wealth of information from electromagnetic waves, including polarization. Using the rich information provided by polarimetry, it is being actively studied in biomedical fields such as cancer and tumor diagnosis. Despite its importance and potential in agriculture, polarimetry for living plants has not been well studied. A Stokes polarimetric imaging system was built to determine the correlation between the polarization states of the light passing through the leaf and the growth states of lettuce. The Stokes parameter s3 associated with circular polarization increased over time and was strongly correlated with the growth of lettuce seedlings. In the statistical analysis, the distribution of s3 followed the generalized extreme value (GEV) probability density function. Salt stress retarded plant growth, and the concentration of treated sodium chloride (NaCl) showed a negative correlation with the location parameter μ of GEV. The clear correlation reported here will open the possibility of polarization measurements on living plants, enabling real-time monitoring of plant health.

Framework for improving DoLP and AoLP reconstruction quality in microgrid polarimeters.

In polarimetric imaging, degree and angle of linear polarization (DoLP and AoLP, respectively) are computed from ratios of Stokes parameters. In snapshot imagers, DoLP and AoLP are degraded by inherent mismatches between the spatial bandwidth of the S0, S1, and S2 parameters reconstructed by demosaicking from microgrid polarizer array (MPA)-sampled data. To overcome this, we rigorously show that log-MPA-sampled data approximately decouples DoLP and AoLP from the intensity component (S0) in the spatial Fourier domain. Based on this analysis, we propose an alternative demosaicking strategy aimed at estimating DoLP and AoLP directly from MPA-sampled data. Our method bypasses Stokes parameter estimation, alleviating the spatial bandwidth mismatch problems altogether and reducing computational complexity. We experimentally verify the superior DoLP and AoLP reconstructions of the proposed log-MPA demosaicking compared to the conventional Stokes parameter demosaicking approach in simulation. We simulated the conventional 2 × 2 MPA patterns as well as the more recently introduced 2 × 4 MPA patterns, and report quantitative results (mean squared error, structural similarity index, and polarization angular error) using five demosaicking approaches drawn from the literature. We also provide a closed-form error analysis on the log-MPA-sampled data to demonstrate that the approximation error is negligible for real practical applications.

Stokes correlation to estimate topological charge from the speckle pattern

The orbital angular momentum (OAM) of the vortex or helical beam, connected with the topological charge (TC) of the beam, has been used as an alternative degree of freedom to encode and decode the information in the optical signals. Many detection schemes have been established to determine the TC configurations and decode the information at the receiver end of the encoded information from the transmitter end for the free space. However, when the helical beam is transmitted through the scattering medium, its wavefront is spatially scrambled without any direct information about the incident helical beam. Here, we propose and experimentally demonstrate a new approach to estimate the TC of the helical beam from the non-imaged randomly scattered pattern. The technique utilizes Stokes parameters (SPs) of the random field to evaluate higher-order SPs fluctuation correlation. A complete theoretical model of the technique is presented and verified with numerical simulation and experimental tests. A good agreement is found between the simulation and experimental results.

Arbitrary Polarization Readout with Dual-Channel Neuro-Metasurfaces.

Polarization, as a vector nature of the electromagnetic wave, plays a fundamental role in optics. Determining the polarization state of light is required by many applications, spanning from remote sensing and material analysis to biology and microscopy. To achieve this goal, conventional methods necessitate cascading of multiple optical components and consequential measurements to estimate the Stokes parameters, rendering the entire optical system bulky, complex, and sensitive. Here a brand-new strategy is introduced for direct polarization readout based on dual-channel neuro-metasurfaces. Neuro-metasurfaces can independently manipulate two orthogonal linearly-polarized waves that can synthesize arbitrary polarization waves with a linear combination. By judiciously designing the output focus points, a unique polarization atlas is created that allows one-to-one correspondence from intensity ratio to polarization state. To implement this, polarization-sensitive metasurfaces are designed and the spatial layout is optimized using a diffractive neural network. The feasibility of this strategy is validated by numerical simulation and microwave experiments. These results pave a new avenue in realizing integrated and multifunctional detectors and demonstrate the potential of neuro-metasurfaces as an add-on for discomposing and composing spatial basis.

Polarization dynamics of a vertical external-cavity surface-emitting laser with a saturable absorber mirror.

We investigate experimentally the polarization dynamics of a vertical external-cavity surface-emitting laser with a saturable absorber mirror in the cavity. We demonstrate that the normalized Stokes parameters and degree of polarization are functions of time reaching extreme values around the pulse peaks. Our experiments show that light is elliptically polarized, being able to have a circular right-handed or left-handed component, depending on the orientation of the saturable absorber mirror.

Simultaneously characterized Stokes parameters of a lightwave utilizing the tensor polarization holography theory.

Polarization is a natural property of a lightwave and makes a significant contribution to various scientific and technological applications, due to the different states of polarization (SoP) of a lightwave that may manifest distinct behaviors. Hence, it is important to determine the SoP of the lightwave. Generally, the SoP of a lightwave can be recognized by the Stokes parameters. In this paper, we proposed a novel method to simultaneously characterize the Stokes parameters of a lightwave, by employing the tensor polarization holography theory. This is done through merely a piece of polarization-sensitive material. Compared with the traditional method, this method requires only one measurement to obtain all the Stokes parameters, without using additional polarizing elements. The experimental result shows excellent agreement with the theoretical one, which confirmed the reliability and accuracy of the proposed method. We believe that this work may broaden the application field of polarization holography.

Manipulation for one-way large-area helical waveguide states in topological heterostructure

Photonic topological insulators (PTIs) have been extensively attracting attention recently because of unique characteristics in manipulating electromagnetic waves. In this work, we construct a kind of heterostructure consisting of a domain of nontrivial topological photonic crystals (TPCs) sandwiched between two domains of trivial TPCs by using all-dielectric materials, systematically analyze and discuss projected photonic bulk bands structures with 3, 5, 6 layers nontrivial TPCs in heterostructures, and theoretically achieve one-way large-area helical topological waveguide states with pseudospin-polarized and robustness. Based on intrinsic chirality of helical edge states, we calculate the chirality map of one-way large-area topological waveguide states by quantifying Stokes parameters. Furthermore, we realize a series of specific manipulation for one-way large-area topological waveguide states, for example, we achieve interesting waveguide functionalities with valley-splitting and four-channel of one-way large-area topological waveguide states in a topological heterostructure with a cross-like route based on chirality map. We realize a wavelength division multiplexing in specific topological heterostructure based on distributions of dispersion curves of topological waveguide states in different heterostructures. The work provide a new promising and valid guideline for practical design and applications in multi-function integrated photonic devices, such as high-capacity energy transport, field enhancement.

Polarimetric analysis of thermal emission from both reciprocal and nonreciprocal materials using fluctuation electrodynamics

Coherent thermal emission for a given polarization has been observed in many metamaterials with micro/nanostructures. Emissivity is typically obtained based on the equivalence between absorptivity and emissivity according to Kirchhoff's law; however, such a relationship may be invalid for nonreciprocal media. This study aims at developing a more general approach, without the constraint of optical reciprocity, that is applicable to magneto-optical materials and magnetic Weyl semimetals. A polarimetric analysis is theoretically carried out based on fluctuation electrodynamics to provide a complete description of the emissivity for all polarization states. The Stokes parameters are calculated from the coherency matrix for a multilayered system, which may include anisotropic media and even nonreciprocal materials. It is demonstrated that thermal emission may be circularly or linearly polarized in selected directions and frequencies. The findings of this work are consistent with the modified Kirchhoff's law provided by several groups in recent years, and therefore, justify the appropriateness of both the direct and indirect methods. This study will help the design of desired thermal emitters for energy harvesting and thermal control.

Precession of magnetars: dynamical evolutions and modulations on polarized electromagnetic waves

ABSTRACT Magnetars are conjectured to be highly magnetized neutron stars (NSs). Strong internal magnetic field and elasticity in the crust may deform the stars and lead to free precession. We study the precession dynamics of triaxially deformed NSs incorporating the near-field and the far-field electromagnetic torques. We obtain timing residuals for different NS geometries and torques. We also investigate the polarized X-ray and radio signals from precessing magnetars. The modulations on the Stokes parameters are obtained for thermal X-rays emitted from the surface of magnetars. For radio signals, we apply the simple rotating vector model (RVM) to give the modulations on the position angle (PA) of the polarization. Our results are comprehensive, ready to be used to search for magnetar precession with timing data and polarizations of X-ray and radio emissions. Future observations of precessing magnetars will give us valuable information on the geometry and the strength of the strong magnetic fields, the emission geometry, as well as the equation of state of NSs.

Polarization Analysis of Gene Sequence Structures: Mapping of Extreme Local Polarization States

A method for visualization and identification of nucleotide sequences is proposed based on the synthesis of phase screens displaying the structure of the analyzed sequences and reconstruction of binary maps of the extreme values of the local Stokes vector components in the diffraction zone. This diffraction zone is formed due to reading out the phase screen by a coherent collimated beam with two orthogonally polarized (x–y) components. With different phase delays of the x–y components of the readout beam introduced by the phase screen elements, this causes a variety of local polarization states in the diffraction zone. The discrimination level for the local component of the Stokes vector chosen for the binary mapping is established near the extreme value for this component. Computer verification of the proposed method using nucleotide sequences for various strains of the model African swine fewer (ASF) virus as the test objects shows its high efficiency in the detection of differences between two compared sequences corresponding to the same type of infectious agent. Analysis of the model data for the strains under study made it possible to establish a power-law character of correlation coefficients of the synthesized binary distributions of extreme local polarization states depending on the discrimination threshold detuning from the maximum value of the Stokes vector component used for the mapping .

Polarization dehazing method based on separating and iterative optimizing airlight from the frequency domain for different concentrations of haze.

Polarization technology has been widely used in imaging through a scattering medium. However, the existing polarization dehazing methods are unstable because they require manual selections of polarization correction parameters. In addition, most of them only focus on the spatial domain without utilizing the frequency domain features, so their dehazing performances are insufficient. In this paper, we propose a polarization dehazing method based on separating and iterative optimizing airlight from the frequency domain. By separating the low-frequency sub-bands of polarization images and refining them as the airlight at three states, we calculated the Stokes parameters of airlight and obtained the preliminary dehazed image. We also propose an iterative optimization approach between the high-frequency sub-band of the dehazed image and airlight to effectively improve the dehazing performance. As a by-product, we introduce our real-world polarization datasets collected in different concentrations of haze. Both the qualitative and quantitative experiments show that our method is effective and robust in different concentrations of haze.

Research on Target Simulation Technology Based on Stokes Vector

With the development of polarization optical technology, polarization detection technology plays a more and more important role in the military and other fields. Existing research demonstrates that the degree of polarization of reflected light from natural objects can often be ignored, while the degree of polarization of artificial objects is relatively large. If the target tracker can identify and track the target with this optical characteristic, the tracking efficiency can be greatly improved. However, at present, there is a lack of testing devices for relevant trackers, and the cost of physical testing is much too high. Therefore, given the lack of an available polarization target simulator, the polarization target simulator based on the Stokes vector is designed. The results show that the polarized target simulator can simulate the polarization target with specific linear polarization information, and the linear polarization degree image and polarization angle image can be obtained by the graphic calculation software.

Evaluation of Scattering by Spacecrafts Using Characteristic Mode Theory Considering Ionosphere Faraday Effect

This article is concerned with developing a viable procedure to evaluate the scattering property of a satellite object. First, to deal with the uncertainty of attitudes of the object with respect to the direction of incidence, the characteristic mode theory is exploited, which is independent of the incident waves. The total scattered field is obtained by summing up the individual characteristic scattered fields with modal weighting coefficients. Second, the ionosphere Faraday effect that may significantly change the polarization behaviors is considered when the frequency is at L-band or below for a ground-based identifying radar. The ionosphere is taken as a sparse and weakly magnetized plasma, and the approximate Wentzel–Kramers–Brillouin method is adopted to calculate the propagations of two intrinsic modes through the ionosphere. The Stokes vector is assumed to be the measured quantities, and the Mueller matrix is employed to fully describe the polarized scattering process.

Estimation of Zernike polynomials for a highly focused electromagnetic field using polarimetric mapping images and neural networks

In this communication, we present a method to estimate the aberrated wavefront at the focal plane of a vectorial diffraction system. In contrast to the phase, the polarization state of optical fields is simply measurable. In this regard, we introduce an alternative approach for determining the aberration of the wavefront using polarimetric information. The method is based on training a convolutional neural network using a large set of polarimetric mapping images obtained by simulating the propagation of aberrated wavefronts through a high-NA microscope objective; then, the coefficients of the Zernike polynomials could be recovered after interrogating the trained network. On the one hand, our approach aims to eliminate the necessity of phase retrieval for wavefront sensing applications, provided the beam used is known. On the other hand, the approach might be applied for calibrating the complex optical system suffering from aberrations. As proof of concept, we use a radially polarized Gaussian-like beam multiplied by a phase term that describes the wavefront aberration. The training dataset is produced by using Zernike polynomials with random coefficients. Two thousand random combinations of polynomial coefficients are simulated. For each one, the Stokes parameters are calculated to introduce a polarimetric mapping image as the input of a neural network model designed and trained for predicting the polynomial coefficients. The accuracy of the neural network model is tested by predicting an unseen dataset (test dataset) with a high success rate.

The Polstar high resolution spectropolarimetry MIDEX mission

The Polstar mission will provide a space-borne 60 cm spectropolarimeter operating at ultraviolet (UV) wavelengths, capturing all four Stokes parameters (intensity, two linear polarization components, and circular polarization). Polstar’s capabilities are designed to meet its goal of determining how circumstellar gas flows alter and inform massive star evolution, affect the stellar remnant population, and stir and enrich the interstellar medium (ISM). These will be achieved by investigating the dynamical geometries in the winds and disks of hot stars, the composition and magnetic alignment of interstellar dust, and the star-forming accretion disks of UV-bright stars at an important transition boundary. Together these areas map out a kind of two-way interface between massive stars and their effect on our galaxy, wherein the stellar winds enrich the ISM with metals and kinetic energy, preconditioning their environment and the stellar endpoints prior to undergoing supernova. The ISM dust in turn reveals the composition and magnetic environment leading to new star formation, and the accretion disks of Herbig Ae/Be stars reveal how the ISM gas returns to make new massive stars. Polstar will combine high-resolution spectroscopy in the time domain with high-precision UV polarimetry. Doppler-shifted UV resonance line opacity will provide information about circumstellar kinematics, while polarization gives complementary geometric information about unseen structures. The composition and magnetic alignment of the smallest interstellar dust grains provides a probe of the ISM utilizing radiative alignment theory (RAT). Polstar will operate in the far-UV (FUV) at 122–200 nm at high spectral resolution of around \(R \sim 30k\), and at FUV and near-UV (NUV) wavelengths of 122–320 nm at lower spectral resolutions of \(0.1-1k\). Detection of polarization levels as weak as 0.1% are expected, with a temporal cadence ranging from 5–10 minutes for most wind variability studies, to hours or days for sampling rotation, to days or weeks for sampling binary orbits, to months to a year for sampling substructure in the inner regions of protoplanetary disks. Sub-meter-class aperture is well suited to access this wide array of time domain science, made possible by restricting to a few hundred bright, massive stars, necessarily extincted by a small to moderate column of interstellar dust, informing both the attributes of the stars and the ISM through which they are seen. As such, the focus is on our own galaxy and its evolutionary drivers, but a few targets in the Magellanic clouds offer the potential to extend this understanding to low-metallicity environments.

Full-Dimensional Surface Characterization Based on Polarized Coherent Coded Aperture Correlation Holography

The coded aperture correlation holography (COACH) is a powerful three-dimensional imaging technique. However, the conventional COACH method can only restore the three-dimensional images of the samples under test, but cannot specify the physical characteristics. We propose a full-dimensional measurement method based on the polarized coded aperture correlation holography. Specifically, the dynamic phase and geometric phase distributions can be separated from two holograms associated with the horizontal and vertical polarization components, then the Stokes parameters, surface topography and reflectivity can be calculated simultaneously. This method achieves the same spatial resolution for the two terms, which greatly improves the reliability and practicability with respect to conventional measurement methods.