Stokes Parameters Research Articles

Poincaré Beams for Magnetic Field Sensing

Poincaré beam (PB), carrying spin angular momentum (SAM) and orbital angular momentum (OAM), plays a significant role in a wide range of optical applications. The inhomogeneous polarization distribution of PB can be represented as a point on the surface of hybrid-order Poincaré sphere (HyOPS). Here, we have investigated the properties of PB propagation in a magnetic fluid under an applied magnetic field. The PB consists of a Gaussian and a vortex beam, which are in orthogonally linear polarization. The Stokes parameters of PB are measured in the experiment to build the Stokes phase profile. Besides, one of the phase contours is marked to analyze the changes of the phase profile. The results show that the phase contours rotate, and the rotation angle is well linearly to magnetic field strength with sensitivity of 0.934°/mT in the range of 2.42 to 27.79 mT, which is consistent with the expectation of the theoretical formula. Our results may contribute to the effort of exploring potential optical sensing at the onset of PB.

Polarized radiative transfer in heterogeneous black carbon aerosol particles

Research on the polarized radiative transfer of black carbon (BC) aerosol particles in the atmosphere is of great help for real-time monitoring of climate change. Existing studies generally have not considered the effects of complex morphology and heterogeneity of BC aerosol particles on the polarized radiative transfer. BC aggregates with different coating shapes are established in accordance with the heterogeneous particle superposition model. The vector Monte Carlo method (VMCM) combined with Discrete dipole approximation (DDA) method proposed in this work offers a general method for calculating the polarized radiative transfer of heterogeneous BC aerosol particles with arbitrary coating shapes. The effects of sulfate coating volumes and shapes, and wavelengths on the Stokes parameters, the degree of polarization P, transmissivity T, and reflectivity R of atmosphere containing heterogeneous BC aerosol particles are discussed. The results show that the simplification of coating shape underestimates the Stokes parameter I and the degree of polarization P of the top of atmosphere and overestimates the I of the bottom of atmosphere. The simplification models of coating shape result in a maximum underestimation of the peak I by ∼26% at the bottom of atmosphere and a maximum overestimation of the peak I by ∼8% at the top of atmosphere, relative to that of the irregular coating models. Moreover, coating volumes and wavelengths also significantly affect the polarized radiative transfer characteristics. Thus, the influence of these factors should be considered for the calculation of polarized radiative transfer of heterogeneous BC aerosol particles in the atmosphere.

Polarization image demosaicing and RGB image enhancement for a color polarization sparse focal plane array.

The color division of focal plane (DoFP) polarization sensor structure mostly uses Bayer filter and polarization filter superimposed on each other, which makes the polarization imaging unsatisfactory in terms of photon transmission rate and information fidelity. In order to obtain high-resolution polarization images and high-quality RGB images simultaneously, we simulate a sparse division of focal plane polarization sensor structure, and seek a sweet spot of the simultaneous distribution of the Bayer filter and the polarization filters to obtain both high-resolution polarization images and high-quality RGB images. In addition, From the perspective of sparse polarization sensor imaging, leaving aside the traditional idea of polarization intensity interpolation, we propose a new sparse Stokes vector completion method, in which the network structure avoids the introduction and amplification of noise during polarization information acquisition by mapping the S1 and S2 components directly. The sparsely polarimetric image demosaicing (Sparse-PDM) model is a progressive combined structure of RGB image artifact removal enhancement network and sparsely polarimetric image completion network, which aims to compensate sparsely polarimetric Stokes parameter images with the de-artifacts RGB image as a guide, thus achieving high-quality polarization information and RGB image acquisition. Qualitative and quantitative experimental results on both self-constructed and publicly available datasets prove the superiority of our method over state-of-the-art methods.

Point Source C-band Mueller Matrices for the Green Bank Telescope

C-band Mueller matrices for the Green Bank Telescope are presented here which enable on-sky Stokes parameters for point sources at the beam center to be determined. Standard calibrators, 3C 138 and 3C 286, were observed using the Spider program to steer the telescope across a broad range of R.A. on both sides of the zenith transit. For this analysis, only the observations at the peak of the Spider pattern were used rather than the full sweep of the runs. Therefore, the results presented here only apply to point sources at the beam center. The Mueller matrices are shown to vary with frequency and with use of the Hi-Cal or Lo-Cal noise diodes, due to the relative calibration gain between the X and Y components of the feed. However, the relative calibration gain can be determined from observations of a source with known polarization. Correcting the data for the relative calibration gain prior to data analysis allows for use of a frequency-independent Mueller matrix. This generic Mueller matrix is shown to provide reliable C-band polarization measurements.

Full-Stokes polarization laser-induced breakdown spectroscopy detection of infiltrative glioma boundary tissue.

The glioma boundary is difficult to identify during surgery due to the infiltrative characteristics of tumor cells. In order to ensure a full resection rate and increase the postoperative survival of patients, it is often necessary to make an expansion range resection, which may have harmful effects on the quality of the patient's survival. A full-Stokes laser-induced breakdown spectroscopy (FSLIBS) theory with a corresponding system is proposed to combine the elemental composition information and polarization information for glioma boundary detection. To verify the elemental content of brain tissues and provide an analytical basis, inductively coupled plasma mass spectrometry (ICP-MS) and LIBS are also applied to analyze the healthy, boundary, and glioma tissues. Totally, 42 fresh tissue samples are analyzed, and the Ca, Na, K elemental lines and CN, C2 molecular fragmental bands are proved to take an important role in the different tissue identification. The FSLIBS provides complete polarization information and elemental information than conventional LIBS elemental analysis. The Stokes parameter spectra can significantly reduce the under-fitting phenomenon of artificial intelligence identification models. Meanwhile, the FSLIBS spectral features within glioma samples are relatively more stable than boundary and healthy tissues. Other tissues may be affected obviously by individual differences in lesion positions and patients. In the future, the FSLIBS may be used for the precise identification of glioma boundaries based on polarization and elemental characterizing ability.

Interface birefringence in asymmetric CdTe/CdZnTe quantum wells

Photoluminescence and polarized reflection spectra of quantum well structures with symmetric ${\mathrm{Cd}}_{0.9}{\mathrm{Zn}}_{0.1}\mathrm{Te}/\mathrm{CdTe}/{\mathrm{Cd}}_{0.9}{\mathrm{Zn}}_{0.1}\mathrm{Te}$ and asymmetric ${\mathrm{Cd}}_{0.9}{\mathrm{Zn}}_{0.1}\mathrm{Te}/\mathrm{CdTe}/{\mathrm{Cd}}_{0.4}{\mathrm{Mg}}_{0.6}\mathrm{Te}$ barriers were studied. The Stokes parameters of the reflected light from these structures were measured. In structures with asymmetric barriers, in the region of exciton resonances, the phenomenon of light birefringence was detected, caused by a lower symmetry of the interfaces compared with the symmetry of bulk crystals. A discussion of this phenomenon is given.

High-performance circular polarization modulation using a dielectric metasurface.

We demonstrate a chiral metasurface that exhibits a giant chiroptical response as well as functions as an optical diode due to geometrical asymmetry for circularly polarized light (CPL). Engineering the Mie-type multipole radiation using geometrical features led to performance values in terms of near-unity transmission and circular dichroism (CD) efficiency (about 0.96) and an extinction ratio of ∼3.8×104 for 1550nm wavelength. A continuous stopband of 1538-1556nm is achieved for an unchosen component of CPL while keeping the transmission efficiency of the chosen CPL component larger than 0.9. Because of the high extinction ratio and CD efficiency, the proposed metasurface has the potential for chiroptical applications including high-contrast polarization imaging, precise Stokes parameters measurement, optical diodes, and polarization detection for CPL.

Performance analysis of a spectropolarimeter employing a continuous phase variation.

The light emitted or reflected by a medium can exhibit a certain degree of polarization. Most of the time, this feature brings valuable information about the environment. However, instruments able to accurately measure any type of polarization are hard to build and adapt to inauspicious environments, such as space. To overcome this problem, we presented recently a design for a compact and steady polarimeter, able to measure the entire Stokes vector in a single shot. The first simulations revealed a very high modulation efficiency of the instrumental matrix for this concept. However, the shape and the content of this matrix can change with the characteristics of the optical system, such as the pixel size, the wavelength or the number of pixels. To assess the quality of the instrumental matrices for different optical characteristics, we analyze here the propagation of errors, together with the impact of different types of noise. The results show that the instrumental matrices are converging towards an optimal shape. On this basis, the theoretical limits of sensitivity on the Stokes parameters are inferred.

Polarized radiative transfer in seawater-in-oil emulsions floated on seawater considering the impact of oil absorption on seawater droplet scattering.

Among various remote sensing approaches, optical polarization remote sensing shows great advantages in identifying oil-water emulsions in seawater and has become one of the most promising detection technologies. Herein, we focus on exploring the sensitivity of polarized radiative transfer properties for oil emulsion polarization detection to the influence factors of viewing angle, droplet volume fraction and radius, incident wavelength, and emulsion thickness. The radiative properties of seawater droplets dispersed in crude oil are calculated using the improved Lorenz-Mie theory considering the absorption of crude oil as the host medium, after which the reflected Stokes vector and the degree of linear polarization (DOLP) of seawater-in-oil emulsions floating on seawater are obtained using the spectral element method. By analyzing the calculation results of a 0° viewing azimuth angle, the detection wavelength and viewing zenith angles corresponding to the highest sensitivity of the DOLP to the above factors are significantly different; thus, quantitative remote sensing detection of the droplet volume fraction, droplet diameter, and emulsion thickness is possible. Exploring the sensitivity of polarized remote sensing signals for oil emulsion polarization detection to the above factors is a prerequisite for quantitative polarization detection of oil emulsions.

Experimental hierarchy of two-qubit quantum correlations without state tomography

A Werner state, which is the singlet Bell state affected by white noise, is a prototype example of states, which can reveal a hierarchy of quantum entanglement, steering, and Bell nonlocality by controlling the amount of noise. However, experimental demonstrations of this hierarchy in a sufficient and necessary way (i.e., by applying measures or universal witnesses of these quantum correlations) have been mainly based on full quantum state tomography, corresponding to measuring at least 15 real parameters of two-qubit states. Here we report an experimental demonstration of this hierarchy by measuring only six elements of a correlation matrix depending on linear combinations of two-qubit Stokes parameters. We show that our experimental setup can also reveal the hierarchy of these quantum correlations of generalized Werner states, which are any two-qubit pure states affected by white noise.

Experimental study of the effect of fallen leaf shading on the polarization characteristics of photovoltaic modules

Coverings have an important impact on the output and safety of photovoltaic (PV) modules. However, due to the complex on-site environment and difficult identification, it is difficult to obtain timely and effective cleaning. In this paper, the optical polarization characteristics of fallen leaf are studied to find the difference for the PV modules with or without fallen leaves covered, which is one of the typical coverings, based on the basic theory of polarization imaging. Firstly, a polarimetric imaging platform with a SALSA camera for PV modules is built. Then, several experiments are conducted and the corresponding images of PV modules shaded by heather or camphor leaves are obtained. Finally, shaded by the impacts on the polarization characteristics of the PV module from fallen leaves, the waveband of the incident light, and the observation angle are analyzed. The results show that the optical polarization characteristics of PV modules at bands of 420 nm and 546 nm are significantly different from others, wherever there existed shading leaves or not; The degree of polarization decreases and then increases with the observation angle from 0° to 70° at 9:00–12:00 a.m. on sunny days; At 0° observation angle, the stokes parameter S_{0} of PV modules with or without fallen leaves has the greatest difference. HighlightsThe influence of fallen leaves on the polarization characteristics of PV modules is studied.The polarization characteristic parameter with the largest difference between the PV modules with and without fallen leaves is obtained.This parameter is more conducive to detecting fallen leaves on the surface of PV modules.

Polarization Raman microscope based on channeled spectropolarimetry

A channeled polarization Raman microscope (CPRM) based on spectrally-modulated polarimetry is introduced. The CPRM modulates the polarization information into a spectrum by an achromatic quarter-wave plate, a high order retarder, and a linear polarizer. The linear Stokes parameters of Raman scattered light can be decoded from this spectrum by the Fourier transformation method (FTM). When compared with the traditional polarization Raman microscope, the proposed system removes the need of rotating the analyzer multiple times for the analysis of the polarization state, thus accelerating the data acquisition process. The feasibility and correctness of CPRM are validated by experiments, and the results of the instrument are shown in point and mapping spectroscopy modes. The results on polypropylene fiber and tooth samples confirm CPRM's abilities to characterize molecular orientation and enhance image contrast.

Optimization of polarization parameters for an LCVR polarization spectrometer under non-oversampling.

The spectral polarization measurement can obtain not only the spectral information of the target but also its polarization information, which can improve the detection and identification of the measured target. In the polarization spectrometer based on a liquid crystal variable retarder (LCVR) and acousto-optic tunable filter (AOTF), the LCVR is a core device for achieving fast and high-precision polarization detection. The AOTF is a new, to the best of our knowledge, filter device for spectral tuning. To reduce the sensitivity of an LCVR-based Stokes polarization spectrometer system to errors and Gaussian noise, and to maintain the advantage of fast electrical tuning of the system for spectral polarization detection, the phase retardation and azimuth angle of the polarization device LCVR is calculated and analyzed optimally under the minimum number of samples N=4 of the Stokes vector measurement method in this paper. The optimization algorithm considers the constraints, such as the number of types of LCVR phase retardation and the number of adjustments, and the azimuth and phase retardation to be optimized are searched for optimality step by step. The simulation results show that the number of adjustments of the phase retardation δ of LCVRs is only three times when four Stokes parameters are obtained. The LCVRs' number of species is four kinds (2×2). The condition number of the optimized measurement matrix is 1.742, which converges to the ideal condition number, the optimal azimuth angle (θ 1,θ 2) is (18.9°, 41.9°), and the optimal phase retardation δ is (179.9°, 156.6°, 0.4°, 46.3°). Its corresponding tetrahedral volume is closer to the ideal value. The optimized system is less sensitive to errors and Gaussian noise.

Simulations on Synchrotron Radiation Intensity and Rotation Measure of Relativistic Magnetized Jet PKS 1502+106

Strong γ-ray outbursts have been observed to emanate from PKS 1502+106, followed by highly variable fluxes in radio, visual, ultraviolet and X-ray bands. Numerical simulations have been conducted to relate the observations to potential theoretical models. The plasma attributes, such as mass density, plasma flow velocity and energy density, cannot be directly observed. However, the Stokes parameters of synchrotron radiation from the plasma can be measured to deduce the plasma attributes. Many studies have been conducted on synchrotron radiation intensity, with only a few on the rotation measure (RM) related to Faraday rotation. In this work, overpressured relativistic magnetized axisymmetric jets are simulated to acquire the synchrotron radiation maps, incorporating Faraday rotation, of the widely discussed jet, PKS 1502+106. The intensity maps and RM maps of the PKS 1502+106 are simulated under practical constraints, and compared with the available observation data to explore specific features of the jet. The simulated intensity maps match well with the observation data in size and shape. The observed spine–sheath polarization structure, sign change in the RM slice and opposite RM gradients have been reproduced. The conjecture of helical magnetic field morphology in the literature has also been validated by comparing the simulation results under different magnetic field morphologies.

White-light channeled imaging polarimeter using Savart plates and a polarization Sagnac interferometer.

A Stokes white-light channeled imaging polarimeter using Savart plates and a polarization Sagnac interferometer (IPSPPSI) is presented, which provides an effective solution to the problem of channel aliasing in broadband polarimeters. The expression for the light intensity distribution and a method to reconstruct polarization information are derived, and an example design for an IPSPPSI is given. The results reveal that a complete measurement of the Stokes parameters in broad band can be achieved with a snapshot on a single detector. The use of dispersive elements like gratings suppresses broadband carrier frequency dispersion so the channels in the frequency domain do not affect each other, ensuring the integrity of information coupled across the channels. Furthermore, the IPSPPSI has a compact structure and does not employ moving parts or require image registration. It shows great application potential in remote sensing, biological detection, and other fields.

Determination of birefringence of biological tissues using modified PS-OCT based on the quaternion approach

Introduction: Polarization-sensitive optical coherence tomography (PS-OCT) is a functional extension of standard OCT. PS-OCT systems can be generally categorized into two categories based on the number of input polarization states on the sample: multi-input polarization state (multi-IPS) and single IPS. In addition, each category includes two configurations: fiber-based system and bulk optics-based system. However, there are complex and time-consuming steps to calibrate the polarization states of light among the reference, the sample, and detection arms for fiber-based system. And it is not compact and robust enough for bulk optics-based system.Methods: In the modified SD PS-OCT system with structural symmetry in both arms of the reference and sample, there are no bulk polarization optical elements in both arms of the reference and the sample. A circularly polarized light was used to incident on sample, and Stokes vector of backscattered light was employed to characterize the birefringence of biological tissues based on the quaternion approach, which directly establishes the relationship between Stokes vectors of backscattered light and Jones matrix of the sample.Results and discussion: The new algorithm provides the analytic solution of retardance and fast-axis orientation. To evaluate the performance of the developed system, an eighth-wave plate is used. Then, the polarization properties of the myocardial tissue in vivo are quantitatively reconstructed based on the quaternion approach. The results demonstrated that the proposed method has an advantage over Jones formalism based on a single input state and two polarization input states. In the future, the modified SD PS-OCT could be improved as a common path SD PS-OCT for clinical applications.

Deep image prior plus sparsity prior: toward single-shot full-Stokes spectropolarimetric imaging with a multiple-order retarder

Compressive full-Stokes spectropolarimetric imaging (SPI), integrating passive polarization modulator (PM) into general imaging spectrometer, is powerful enough to capture high-dimensional information via incomplete measurement; a reconstruction algorithm is needed to recover 3D data cube (x, y, and λ) for each Stokes parameter. However, existing PMs usually consist of complex elements and enslave to accurate polarization calibration, current algorithms suffer from poor imaging quality and are subject to noise perturbation. In this work, we present a single multiple-order retarder followed a polarizer to implement passive spectropolarimetric modulation. After building a unified forward imaging model for SPI, we propose a deep image prior plus sparsity prior algorithm for high-quality reconstruction. The method based on untrained network does not need training data or accurate polarization calibration and can simultaneously reconstruct the 3D data cube and achieve self-calibration. Furthermore, we integrate the simplest PM into our miniature snapshot imaging spectrometer to form a single-shot SPI prototype. Both simulations and experiments verify the feasibility and outperformance of our SPI scheme. It provides a paradigm that allows general spectral imaging systems to become passive full-Stokes SPI systems by integrating the simplest PM without changing their intrinsic mechanism.

Faraday rotation and ellipticity spectroscopy between excited states of Rb vapor: Theory and experiment

The Faraday rotation and ellipticity spectra of rubidium $5{P}_{3/2}\ensuremath{\rightarrow}4{D}_{5/2}$ transition in a magnetic field have been calculated and experimentally measured. By using the rotating quarter-wave plate method, the Stokes parameters of the $5{P}_{3/2}\ensuremath{\rightarrow}4{D}_{5/2}$ near-resonant probe light are measured to obtain the Faraday rotation and the ellipticity. The variation of the rotation and the ellipticity spectra is analyzed in different magnetic fields, temperatures, and pump powers. The polarization rotation over 50 deg in 1529 nm with negligible elliptical distortion is obtained. Our study of the Faraday effect between excited states of atoms broadens the available wavelength of the Faraday effect in applications.

Poincare vector correlations to estimate polarization dynamics in the laser speckle

We propose and experimentally demonstrate a new method to measure the spatial polarization dynamics of laser speckles. This is realized by using the concept of the Poincare vector correlations and experimentally measured Stokes parameters. Two-point correlations of the Stokes parameters offer a new and stable experimental technique to determine the Poincare vector correlations and characterize the polarization fluctuations of the laser speckle. The use of two-point Stokes correlations in the evaluation of spatial polarization dynamics offers a new method and the performance of this technique is tested by evaluating the spatial polarization dynamics of three different cases of the laser speckles. Experimental results are also tested and compared with the simulations results and good agreement between simulation and experimental results confirm the accuracy and usefulness of our technique in the characterization of the polarization dynamics.

Paradigmatic examples for testing models of optical light polarization by spheroidal dust

We present a general framework on how the polarization of radiation due to scattering, dichroic extinction, and birefringence of aligned spheroidal dust grains can be implemented and tested in 3D Monte Carlo radiative transfer (MCRT) codes. We derive a methodology for solving the radiative transfer equation governing the changes of the Stokes parameters in dust-enshrouded objects. We utilize the Müller matrix and the extinction, scattering, linear, and circular polarization cross sections of spheroidal grains as well as electrons. An established MCRT code is used, and its capabilities are extended to include the Stokes formalism. We compute changes in the polarization state of the light by scattering, dichroic extinction, and birefringence on spheroidal grains. The dependency of the optical depth and the albedo on the polarization is treated. The implementation of scattering by spheroidal grains both for random walk steps as well as for directed scattering (peel-off) are described. The observable polarization of radiation of the objects is determined through an angle binning method for photon packages that leaves the model space as well as through an inverse ray-tracing routine for the generation of images. We present paradigmatic examples for which we derive analytical solutions of the optical light polarization by spheroidal dust particles. These tests are suited for benchmark verification of MCPOLand other such codes and allow the numerical precision reached by these codes to be quantified. We demonstrate that MCPOLis in excellent agreement (within ~0.1%) of the Stokes parameters when compared to the analytical solutions.