Degree Of Polarization Values Research Articles

Probing the enpolarization phenomenon in a speckle pattern using a microwave photonics-inspired approach.

We report how Stokes polarimetry of a highly resolved optical speckle pattern coupled to an original microwave photonics-inspired experimental approach allows new light to be shaded on the so-called enpolarization phenomenon, which consists in the local increase of the light degree of polarization (DOP) inducing a high average DOP value after interaction of unpolarized light with a totally depolarizing sample.

Tracking post-storage apple age with polarized light measurements

A rotating retarder fixed polarizer (RRFP) polarimeter operating in the 600 – 1000 nm range was developed and used to measure the polarized reflected light response of post-storage apples. The degree of polarization (DOP) changes on two apple cultivars, Malus x domestica Borkh. (‘Scired’, marketed as Bay Queen®) and Malus x domestica Gala (‘Royal Gala’), was measured as the apples aged at room temperature and humidity (∼22 °C and 65%RH respectively) over an 18-day period. The DOP values were highest at 600 nm with observable peaks around the chlorophyll-related absorption at 675 nm, especially for the Bay Queen cultivar, and around the water-related absorption at 970 nm. The values between 700 and 900 nm were featureless and flat at half the peak values. The DOP values for circularly polarized light were about 50% lower over most of the spectral range than those for linearly polarized light. Overall, the DOP values decreased with apple age. There was a strong linear trend for individually tracked apples that was well correlated with non-destructive impact probe firmness measurements. The DOP loss rate was highest below 700 nm, peaking notably for Bay Queen at 675 nm, and is consistent with a probable loss with aging of visible-range pigment absorbers in the near surface region. In contrast, the DOP loss rate was spectrally near flat above 700 nm, suggesting there are no near-infrared absorber losses in the near surface region of the fruit. There was no evidence of an increased DOP loss rate near the water absorption peak at 970 nm, suggesting the water concentration in the near surface region is effectively constant over the 18-day aging period and despite a 5% total loss of water from the whole fruit. While the individually tracked apples trended linearly with age and correlated with non-destructive firmness, the relationships were very inconsistent between the apples. Also, no trends with age or correlations with firmness could be established for measurements on other untracked apples sampled independently from the same aging populations and tested destructively at each day. It is surmised that DOP reflectance measurements are unlikely to be useful for the direct and non-destructive prediction of internal fruit quality parameters such as firmness.

Stokes–Mueller polarization-based analysis of model SARS-CoV-2 virions

Understanding the virology of the coronavirus at the structural level has gained utmost importance to overcome the constant and long-term health complications induced by them. In this work, the light scattering properties of SARS-CoV-2 of size 140 nm were simulated by using discrete dipole approximation (DDA) for two incident wavelengths 200 nm and 350 nm, respectively. Three different 3-dimensional (3D) models of SARS-CoV-2 corresponding to 15, 20, and 40 numbers of spike proteins on the viral capsid surface were constructed as target geometries for the DDA calculations. These models were assessed by employing Stokes–Mueller polarimetry to obtain individual polarization properties such as degree of polarization (DOP), degree of linear polarization (DOLP), and degree of circular polarization (DOCP). Irrespective of its spike numbers, all the coronavirus models were found to display higher DOP and DOCP values and negligibly small DOLP values for circularly polarized incident light, indicating the presence of chiral structures. On the other hand, the lack of understanding about the dependence of the Mueller matrix on its microstructural properties was overcome by transforming 16 Mueller elements into sub-matrices with specific structural and physical properties using Lu–Chipman-based Mueller matrix polar decomposition method. The obtained properties such as retardance, diattenuation, and depolarization were used for investigating the composition and microstructural information. The approach presented in this work has the potential to understand the virology of the coronavirus at the structural level and, therefore, will be beneficial in developing effective detection strategies by exploiting their characteristic electromagnetic scattering signatures.

Statistical properties of double-slit interference of partially coherent polarization singular vector beams

The Young’s double-slit interference of partially coherent polarization singular vector beams (PC-PSVBs) is investigated both theoretically and experimentally. Unlike the case of scalar or linearly polarized light beams, the far-field interference pattern of PC-PSVB’s have spatial dependence both in horizontal and vertical directions. The visibility of these patterns is governed by the input spatial correlation length. The number of minima along the vertical direction (y-axis) depicts the magnitude of Poincaré-Hopf index (PHI) of the incident beam. Our results reveal that the far-field statistical properties namely, intensity pattern, degree of polarization (DOP) distribution and Stokes-parameters distributions of the PC-PSVBs diffracted through a double-slit are strongly influenced by the spatial correlation length of the incident beam. It is observed that the DOP distribution of the diffracted PC-PSVB does not follow the azimuthally symmetric DOP profile of the input PC-PSVB. Interestingly, the DOP distributions contain the information of the magnitude of PHI of the incident PC-PSVB even for a low value of spatial correlation length. However, the maximum value of DOP deteriorates with the decrease in the input spatial correlation length. Furthermore, the Stokes field (S12(ρ,z)) of the diffracted PC-PSVB contains the information of both the magnitude and polarity of the PHI of the input beam. The experimental results are in good agreement with the theoretical predictions, and may find applications in the areas where the statistical properties of a light field are important.

Sensor Modeling and Calibration Method Based on Extinction Ratio Error for Camera-Based Polarization Navigation Sensor.

The performance of camera-based polarization sensors largely depends on the estimated model parameters obtained through calibration. Limited by manufacturing processes, the low extinction ratio and inconsistency of the polarizer can reduce the measurement accuracy of the sensor. To account for the challenges, one extinction ratio coefficient was introduced into the calibration model to unify the light intensity of two orthogonal channels. Since the introduced extinction ratio coefficient is associated with degree of polarization (DOP), a new calibration method considering both azimuth of polarization (AOP) error and DOP error for the bionic camera-based polarization sensor was proposed to improve the accuracy of the calibration model parameter estimation. To evaluate the performance of the proposed camera-based polarization calibration model using the new calibration method, both indoor and outdoor calibration experiments were carried out. It was found that the new calibration method for the proposed calibration model could achieve desirable performance in terms of stability and robustness of the calculated AOP and DOP values.

Clear Night Sky Polarization Patterns Under the Super Blue Blood Moon

Investigating celestial polarization patterns in the case of different environments is important for exploring the atmospheric radiative transfer mechanism. Although intensive studies on clear sky, foggy sky, and even total solar eclipse sky have been conducted, the polarization distribution generated by the moonlight has not been well investigated. This study analyzes celestial polarization patterns generated by the Super Blue Blood Moon (SBBM) through several comparative studies. The polarization patterns under the SBBM are collected, analyzed, and compared with both those generated by the ideal single-scattering Rayleigh model and those in the normal sky. From the analysis of the relative variation of the celestial polarization characteristics including the Degree of Polarization (DoP) and Angle of Polarization (AoP), the changes of the extremum, frequency, symmetric line, and neutral points are discussed. As a result, SBBM polarization patterns change at the beginning of the partial eclipse, and the neutral points vary from traditional neutral points. The value of DoP gradually decreases as the obscuration ratio of the Moon increases. The AoP is no longer symmetrical about the celestial meridian. As a conclusion, it is suggested that the variation of the polarized skylight during the SBBM should be considered in atmospheric model calculation for nocturnal biological activity and navigation information computation.

A Bio-Inspired Navigation Strategy Fused Polarized Skylight and Starlight for Unmanned Aerial Vehicles

The migratory animals are capable of traveling long distances by fusing varied information, such as the halteres, the star positions, and the polarization pattern. Motivated by the navigation strategy of migratory animals, a bio-inspired navigation strategy based on polarized skylight, starlight, and halteres is presented in this paper. To enhance the environmental adaptability of the polarization navigation system, a sun vector calculation method tightly fusing the degree of polarization (DoP) and the azimuth of polarization (e-vector) is proposed. By setting the threshold of DoP values of the observation points, the DoP and the e-vector within the threshold range can be selected to deduce the sun position. As such, the robustness and reliability of the sun position can be improved. Concerned with the issue of attitude and heading determination in GNSS-challenged conditions, an integrated navigation strategy combined with polarized light and starlight is proposed. In addition, a Kalman filter is adopted to fuse the navigation data of polarized light, starlight, and inertial sensors. Finally, simulations are conducted to validate the performance of the integrated model. The results illustrated that the proposed navigation strategy is capable of determining the attitude and heading in the scenarios of which the Global Navigation Satellite System (GNSS) is disturbed.

Degree of polarization modeling based on modified microfacet pBRDF model for material surface

The polarized bidirectional reflectance distribution function (pBRDF) can effectively simulate the degree of polarization (DoP) characteristics of material surface. Most of the existing pBRDF models include a Lambertian constant diffuse scattering component that the scattering and absorption of light inside the material is completely ignored. In this paper, a modified microfacet pBRDF model is proposed for material surface with considering specular reflection and diffuse scattering based on the combination of the microfacet and Kubelka–Munk (K–M) theory. In this model, a scaling parameter is introduced into specular reflection component to adjust the model which contains all the polarization information, and the diffuse scattering component is depolarization modeled following the K–M theory. The expression of DoP is developed from the new pBRDF model that includes the scattering and absorption effects in bulk of material, which makes more reasonable with physical interpretation. Several experiment groups of DoP for coating samples (rough yellow and black paint) are measured by the multi-angle polarization instrument, and then, the model parameters are fitted by least square method based on the experimental data. The results show that the DoP values calculated by the modified microfacet pBRDF model are found to be consistent with the measured DoP values, and can significantly improve the modeling accuracy, which provides theoretical support for polarization remote sensing and object recognition.

Strain modulated nanostructure patterned AlGaN-based deep ultraviolet multiple-quantum-wells for polarization control and light extraction efficiency enhancement

AlGaN-based deep ultraviolet (DUV) multiple-quantum-wells (MQWs) incorporating strain-modulated nanostructures are proposed, demonstrating enhanced degree of polarization (DOP) and improved light extraction efficiency (LEE). The influence of Al composition and bi-axial strains on the optical behaviors of the DUV-MQWs were carefully examined. Compared with planar DUV-MQWs, strain-modulated nanostructure patterned MQWs show three times higher photoluminescence and increased DOP from −0.43 to −0.16. Moreover, nanostructure patterned DUV-MQWs under compressive strains further illustrate higher DOP and LEE values than those under tensile strains due to more efficient diffraction of the guided modes of the transverse electric (TE) polarized light. Our work demonstrates, for the first time, that a combination of compressive in-plane strain and surface nanostructure show unambiguous advantages in facilitating TE mode emission, thus have great promises in the design and optimization of highly efficient polarized DUV optoelectronic devices.

On the validity domain of approximations to estimation variance of polarization degree, azimuth, and ellipticity.

We determine the validity domain of classical approximations to estimation variance of the degree of polarization (DOP), angle of polarization, and ellipticity (EOP), when the measurement matrix of the Stokes vector is a spherical 2 design and noise is additive, white, and Gaussian. We demonstrate that this domain of validity is quite large, so that these approximations can be used safely for back-of-the-envelope calculations. In the presence of strong noise, DOP and EOP approximations show, however, some limits. We thus derive other approximations with extended domain of validity that can account for the dependence of DOP and EOP estimation variance on actual DOP and EOP values. The obtained results are important for design and performance characterization of polarimeters.

Highly Polarized Fluorescent Film Based on Aligned Quantum Rods by Contact Ink-Jet Printing Method

Fluorescent quantum rods (QRs) have received much attention recently because of their properties of polarized light emission with narrow full width at half-maximum. Therefore, QRs can be used in liquid crystal display (LCD) backlight, as an active polarizer. In order to emit light with a high degree of polarization (DOP), QRs need to be controlled and aligned along one direction on large-scaled devices. However, most of the proposed effective alignment approaches cannot be applied to a large area. In this paper, we report for the first time the contact ink-jet printing (CIJP) method to align CdSe/CdS core/shell QRs. With the ink being printed, the QRs can align along the fluid ink flow direction resulting in aligned QRs along printing direction and forming a film with a high DOP of 42%. Furthermore, CIJP can realize arbitrarily large area fabrication without reducing DOP value. It is expected that this method can be utilized to print on large-scaled substrates directly to fabricate polarized optoelectronic devices, and further applied to LCD backlights and any other applications where polarized light is needed.

P‐14.1: Highly Polarized Aligned Quantum Rods Fluorescent Film Based on Contact Ink‐Jet Printing Method

In recent years, fluorescent quantum rods (QRs) receive much attention because of their properties of emitting specific wavelength polarized light with narrow full width at half maximum (FWHM). Therefore, QRs are usually aligned on devices, such as light emitting diodes, laser, and liquid crystal display (LCD), as a polarizer. In order to emit the light with a high degree of polarization (DOP), QRs need to be controlled and aligned almost along one direction on large‐scaled devices. However, most of the proposed effective alignment approaches cannot be applied to a large area. Hence, we firstly propose the contact ink‐jet printing (CIJP) method to align CdSe/CdS core/shell QRs. With the ink being printed, the QRs can move driven by ink flowing. Eventually, the QRs will be aligned along the printed trajectories and become a film with DOP of more than 40%. Furthermore, CIJP can realize arbitrarily large area fabrication without reducing DOP value. In the future, this method can be utilized to print on large‐scaled substrates directly to fabricate polarized optoelectronic devices, and further applied to LCD backlights and optical lenses.

Expression of the degree of polarization based on the geometrical optics pBRDF model.

An expression of the degree of polarization (DOP) based on the geometrical optics polarimetric bidirectional reflectance distribution function model is presented. In this expression, the DOP is related to the surface roughness and decreases at different reflection angles because diffuse reflection is taken into consideration. A shadowing/masking function introduced into the specular reflection expression makes the DOP values decrease as the angle of incidence or observation approaches grazing. Different kinds of materials were measured to validate the accuracy of this DOP expression. The measured results suggest that the errors of the DOP are reduced significantly, and the polarized reflection characteristics can be described more reasonably and accurately.

Modified polarimetric bidirectional reflectance distribution function with diffuse scattering: surface parameter estimation

The polarimetric bidirectional reflectance distribution function (pBRDF) describes the relationships between incident and scattered Stokes parameters, but the familiar surface-only microfacet pBRDF cannot capture diffuse scattering contributions and depolarization phenomena. We propose a modified pBRDF model with a diffuse scattering component developed from the Kubelka–Munk and Le Hors et al. theories, and apply it in the development of a method to jointly estimate refractive index, slope variance, and diffuse scattering parameters from a series of Stokes parameter measurements of a surface. An application of the model and estimation approach to experimental data published by Priest and Meier shows improved correspondence with measurements of normalized Mueller matrix elements. By converting the Stokes/Mueller calculus formulation of the model to a degree of polarization (DOP) description, the estimation results of the parameters from measured DOP values are found to be consistent with a previous DOP model and results.

Electromagnetic Schell-model sources generating far fields with stable and flexible concentric rings profiles.

A class of electromagnetic sources with multi-cosine Gaussian Schell-model correlation function is introduced. The realizability conditions for such sources and the beam conditions for the beams generated by them are established. Analytical formulas for the cross-spectral density matrix of such beams propagating in free space are derived and used to examine their statistical properties by numerical simulations. The results demonstrate that such beams possess invariant far-field concentric rings-like intensity patterns, uniform polarization state on all rings, and generally different degree of polarization values on different rings. By changing the summation index and other source parameters, the number of rings along with the behavior of various beam characteristics can be tuned at will.

Anisotropic Properties of Ultra-Thin Freestanding Multi-Walled Carbon Nanotubes Film for Terahertz Polarizer Application

Anisotropic transmission of ultrathin freestanding multi-walled carbon nanotubes (MWCNTs) film has been investigated using terahertz (THz) time-domain spectroscopy. The super-aligned MWCNTs films were fabricated by a novel method—drawing and winding carbon nanotubes on square-shaped polytetrafluoroethylene (PTFE) frame. The MWCNTs film exhibited anisotropic transmittance of THz wave depending on the alignment direction of carbon nanotubes relative to the THz wave polarization orientation, which proved that such MWCNTs film acts as an ideal polarizer in the THz regime. The degree of polarization (DOP) of 99.4% and the extinction ratio (ER) of 25.3 dB (average value) has been demonstrated for a MWCNTs film of 9- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> thickness in a wide frequency range from 0.1 to 2.5 THz. Furthermore, the value of DOP and ER can be engineered expediently by controlling the film thickness. Our approach opens the possibility of MWCNTs film in application of THz optoelectronic devices.

Complex index of refraction estimation from degree of polarization with diffuse scattering consideration.

The estimation of the refractive index from optical scattering off a target's surface is an important task for remote sensing applications. Optical polarimetry is an approach that shows promise for refractive index estimation. However, this estimation often relies on polarimetric models that are limited to specular targets involving single surface scattering. Here, an analytic model is developed for the degree of polarization (DOP) associated with reflection from a rough surface that includes the effect of diffuse scattering. A multiplicative factor is derived to account for the diffuse component and evaluation of the model indicates that diffuse scattering can significantly affect the DOP values. The scattering model is used in a new approach for refractive index estimation from a series of DOP values that involves jointly estimating n, k, and ρ(d)with a nonlinear equation solver. The approach is shown to work well with simulation data and additive noise. When applied to laboratory-measured DOP values, the approach produces significantly improved index estimation results relative to reference values.

Suspended GaN-based band-edge type photonic crystal nanobeam cavities

We demonstrated GaN-based photonic crystal (PC) nanobeam cavities by using the e-beam lithography and the suspended nanobeams were realized by focused-ion beam (FIB) milling. One resonant mode was clearly observed at 411.7 nm at 77K by optical pumping. The quality factor was measured to be to 7.4 × 10(2). Moreover, the degree of polarization value was measured to be 40%. The temperature-dependent characteristics were measured and discussed, which unambiguously demonstrated that the observed resonant peak originated from the band-edge mode of the one-dimensional PC nanobeam.

Theoretical and experimental comparison between power and degree of polarization based optical fiber current sensors

This paper presents a theoretical and experimental comparison of two techniques of optical fiber current sensors (OFCS) based on the Faraday Effect: the power and the degree of polarization (DOP) methods. The DOP method is shown to be insensitive to state of polarization (SOP) changes induced by environmental conditions. A maximum variation of 0.4% in the DOP value in the entire range of applied current from 0 to 100 A was measured. It is the first time to our knowledge that this fact was experimentally verified. Also, for the first time known it is reported that zero current response, DOP = 0.996, is in agreement with the theoretical expected value of unitary DOP. Besides, the theoretical and experimental normalized DOP is shown to have a maximum difference of 0.33% in the entire range of applied current. On the other hand, the power method OFCS is greatly affected by SOP changes. In order to be used in a practical application, its complexity must be increased by the use, for example, of polarization maintaining fibers instead of standard fibers used in the DOP method, increasing the cost of the sensor element.

Assessment of magneto-optic Faraday effect-based drift on interferometric single-mode fiber optic gyroscope (IFOG) as a function of variable degree of polarization (DOP)

In this study, a novel interferometric fiber optic gyroscope (IFOG), which has a different depolarizer structure, is designed in TUBITAK UME (National Metrology Institute of Turkey) to experimentally and relatively evaluate the effect of the degree of polarization on the Faraday effect-based drift of the light waves injected into both arms of a Sagnac interferometer. In order to observe whether or not any change occurs in the Faraday-based drift, depending on the variations in degree of polarization (DOP), a triple structure-depolarizer IFOG possessing adjustable DOP is firstly designed and prototyped. The minimum DOP achieved with triple structure-depolarizers is typically 0.15% for both clockwise (CW) and counterclockwise (CCW) light waves at both arms of the Sagnac interferometer. The experimental evaluations about the drift are given for DOP changes extending from 78.00% to 0.15% together with two main and different theoretical approaches in the literature. According to the experimental evaluations given herein, it is experimentally proved that the Faraday-based drift does not change depending on DOP values of both CW and CCW light waves injected into the single-mode (SM) sensing coil and it is impossible to state a concept of a depolarized IFOG by considering the polarization state at the entrance arms of the SM sensing coil.