Polarization Of Scattered Light Research Articles

Impact of hot exozodiacal dust on the polarimetric analysis of close-in exoplanets

Context. Hot exozodiacal dust (HEZD) found around main-sequence stars through interferometric observations in the photometric bands H to L is located close to the dust sublimation radius, potentially at orbital radii comparable to those of close-in exoplanets. Consequently, HEZD has a potential influence on the analysis of the scattered-light polarization of close-in exoplanets and vice versa. Aims. We analyze the impact of HEZD on the polarimetric characterization of close-in exoplanets. This study is motivated in particular by the recently proven feasibility of exoplanet polarimetry. Methods. Applying the 3D Monte Carlo radiative transfer code POLARIS in an extended and optimized version for radiative transfer in exoplanetary atmospheres and an analytical tool for modeling the HEZD, we simulated and compared the polarization characteristics of the wavelength-dependent scattered-light polarization of HEZD and close-in exoplanets. As a starting point for our analysis, we defined a reference model consisting of a close-in exoplanet with a scattered-light polarization consistent with the upper limit determined for WASP-18b, and a HEZD consistent with the near-infrared excess detected for HD 22484 (10 Tau). Results. The varied parameters are the planetary phase angle (0°–180°), the dust grain radius (0.02 µm−10 µm), the HEZD mass (10−10 M⊙−10−8 M⊙), the orbital inclination (0°−90°), the composition of the planetary atmosphere (Mie and Rayleigh scattering atmosphere), the orbital radius of HEZD (0.02 au−0.4 au), and the planetary orbital radius (0.01 au−0.05 au). The dust grain radius has the strongest influence on the polarimetric analysis due to its significant impact on the wavelength-dependent polarization characteristics and the total order of magnitude of the scattered-light polarization. In certain scenarios, the scattered-light polarization of the HEZD even exceeds that of the close-in exoplanet, for example for a dust grain radius of 0.1 µm, a HEZD mass of 8 × 10−10 M⊙, an orbital radius of HEZD of 0.04 au and an orbital inclination of 90°. Conclusions. The presence of HEZD potentially has a significant impact on the polarimetric investigations of close-in exoplanets. Furthermore, interferometric observations are required to better constrain the parameter space for HEZD and thus the possible resulting scattered-light polarization.

Scattered polarized radiation of extrasolar circumplanetary rings

Aims. We have investigated the impact of circumplanetary rings consisting of spherical micrometer-sized particles on the net scattered light polarization of extrasolar gas giants. Methods. Using the three-dimensional Monte Carlo radiative transfer code POLARIS, we studied the impact of the macroscopic parameters that define the ring, such as its radius and inclination, and the chemical composition of the ring particles on the net scattered polarization. For the spherical ring particles, we applied the Mie scattering theory. We studied the flux and polarization of the scattered stellar radiation as a function of planetary phase angle and wavelength from the optical to the near-infrared. Results. For the chosen grain size distribution, the dust particles in the ring show strong forward scattering at the considered wavelengths. Thus, the reflected flux of the planet dominates the total reflected and polarized flux at small phase angles. However, the scattered and polarized flux of the ring increase at large phase angles and exceeds the total reflected planetary flux. For large rings that contain silicate particles, the total reflected flux is dominated by the radiation scattered by the dust in the ring at all phase angles. As a result, the orientation of polarization is parallel to the scattering plane at small phase angles. In contrast, for a ring that contains water ice particles, the orientation of polarization is parallel to the scattering plane at large phase angles. Depending on the ring inclination and orientation, the total reflected and polarized flux show a specific distribution as well. Large particles show a strong polarization at large phase angles compared to smaller particles. For a Jupiter-like atmosphere that contains methane and aerosols, methane absorption features are missing in the spectrum of a ringed planet. Conclusions. Scattering of the stellar radiation by dust in circumplanetary rings of extrasolar planets results in unique features in the phase-angle- and wavelength-dependent reflected and polarized net flux. Thus, exoplanet polarimetry provides the means to study not only the planetary atmosphere and surface, but also to identify the existence and constrain the properties of exoplanetary rings.

Research on polarization characteristics of background light by modified polarization difference imaging method

<sec>The random scattering event of light by water medium is the primary reason for the degradation in underwater imaging. Underwater polarization imaging technology can enhance the signal-to-noise ratio of imaging effectively by utilizing the polarization information difference between background scattered light and target light. However, as scattering events increase in the water body, it is difficult to maintain the polarization characteristics of light, which reduces the effect of removing scattering based on polarization characteristics. In addition, the polarization rule of background scattered light in water is unclear, and there is a lack of quantitative description of the polarization characteristics of scattered light. Therefore, the study of polarization transmission characteristics of underwater scattered light is of great significance in reducing the scattering light of underwater polarization imaging.</sec><sec>In order to clarify the polarization characteristics of underwater background scattered light, especially the polarization angle information, this paper proposes a method for ascertaining polarization angle of background light based on modified polarization difference imaging method. In this method, the coupling relationship between optimal weight coefficient and enhancement measure evaluation (EME) value of the Stokes vector difference result is analyzed, and the background light polarization angle is calculated based on the optimal weight coefficient. Combined with the experimental results, the EME distribution trend of the optimal weight coefficient and the modified polarization difference imaging method results in different turbidity water bodies are determined, the scattering suppression limit is explored, and the trend of background scattered light polarization direction with turbidity of water is analyzed. The results show that the proposed method can obtain the exact polarization angle of background scattered light in different water environments, revealing a trend that the polarization direction of background scattered light becomes orthogonal to the incident light direction as the turbidity of the water increases. This research provides a methodological basis for determining the polarization direction of the background scattered light in underwater imaging.</sec>

Calibration by Air in Polarization Sensing

Scattered light polarization serves as an indicator and a characteristic of various processes in the atmosphere. The polarization measurements of all scattering matrix elements provide an adequate description of the optical and morphological parameters and orientation of particles in clouds. In this article, we consider the problem of the calibration of matrix polarization lidar (MPL) parameters. Calibration by air is an effective alternative to the technique for correcting optical element parameters and among the calibration parameters of the MPL optical path are the relative transmission coefficient of a two-channel receiver, the angular positions of the transmission axes of the optical elements of the transmitter and receiver units, including the polarizers and wave plates, and the retardance of wave plates. For the first time, the method of calibration by air was partially implemented in the MPL to study Asian dust in the atmosphere. We considered the calibration problem more generally and this was due to the need to calibrate different MPL modifications from stationary to mobile ones. The calibration equations have been derived in terms of instrumental vectors, and the method of their solution by the generalized least squares method has been proposed. The method has been verified on a numerical MPL model and validated using MPL measurements in Daejeon, Republic of Korea.

Numerical simulation of scattered light polarization in a developing convective cloud for millimeter wavelengths

The optical characteristics of scattered light polarization in a developing convective cloud for millimeter wavelengths are numerically studied using the convection jet model and Stokes parameters. The analysis revealed that the value of all polarization forms does not depend on the cloud droplet spectrum and wavelength in the lower layers of a convective cloud. As the cloud droplet size increases and the wavelength decreases, the polarizations of all forms vary greatly and may have several maxima. It is also demonstrated that the degree of partial polarization may make no sense in the Rayleigh region at the certain values of polarization parameters.

LABORATORY SIMULATION OF LIGHT SCATTERING FROM REGOLITH ANALOGUES: EFFECT OF POROSITY

The surfaces of most atmosphereless solar system objects are referred to as regolith, layers of looselyconnected fragmentary debris, produced by meteorite impacts. Measurements of light scattered fromsuch surfaces provides information about the composition and structure of the surface. A suitable wayto characterize the scattering properties is to consider how the intensity and polarization of scatteredlight depends on the particle size, composition, porosity, roughness, wavelength of incident light andthe geometry of observation. In the present work, the e ect of porosity on bidirectional reectance asa function of phase angle is studied for alumina powder with grain size of 0.3 m and olivine powderwith grain size of 49 m at 543.5 nm. The optical constants of the alumina sample for each porositywere calculated with Maxwell Garnett e ective medium theory. On using each of the optical constants ofalumina sample in Mie theory with the Hapke model the variation of bidirectional reectance is obtainedas a function of phase angle with porosity as a parameter. Experimental reectance data are in goodagreement the model. For the olivine sample the e ect of porosity is studied using Hapke (2008).Key words: bidirectional reectance: EMT-porosity-regolith-scattering1. INTRODUCTIONThe study of light scattering by planetary regolith hasbeen and continues to a subject of great interest in manydi erent scienti c disciplines for many years. Labora-tory photometry of regolith-like samples is important forinterpreting the phase curves which are being used as aplanetary surface characterization tool. Consequently,laboratory based experiments on regolith analogues arebecoming more signi cant, so that in situ data can beanalyzed using laboratory results.2. INSTRUMENTAL DETAILSThe laboratory simulation was performed with the helpof a gonio-photometric device at the department ofPhysics, Assam University, Silchar, India. It consistsof two metal arms having a common horizontal axis ofrotation. The two arms can be rotated by 90

Seeing Double: Coupling between Substrate Image Charges and Collective Plasmon Modes in Self-Assembled Nanoparticle Superstructures

The interaction between adjacent metal nanoparticles within an assembly induces interesting collective plasmonic properties. Using dark-field imaging of plasmon scattering, we investigated rings of gold nanoparticles and observed that the images were dependent on the substrate. In particular, for nanoparticles assembled on carbon and gold substrates, intensity line sections perpendicular to the ring revealed a significant broadening beyond the optical resolution accompanied by an intensity dip in the middle of the line profile. Overall, this appeared in the image as a "splitting" into two offset circles along the direction of the scattered light polarization. This effect was not observed for a substrate with a low permittivity, such as glass. By varying the substrate as well as selecting different detected wavelengths and polarization components of the excitation light, we were able to confirm that the observed effect was due to coupling of collective plasmon modes with their induced image charges in the supporting substrates. These results suggest that plasmon scattering in extended nanostructures can be spatially modulated by tuning the permittivity of the substrate.

Coherent control of nuclear forward scattering

The possibility to control the coherent decay of resonant excitations in nuclear forward scattering is investigated. By changing abruptly the direction of the nuclear hyperfine magnetic field, the coherent scattering of photons can be manipulated and even completely suppressed via quantum interference effects between the nuclear transition currents. The efficiency of the coherent decay suppression and the dependence of the scattered light polarization on the specific switching parameters is analyzed in detail. Using a sophisticated magnetic switching sequence involving four rotations of the hyperfine magnetic field, two correlated coherent decay pulses with different polarizations can be generated out of one excitation, providing single-photon entanglement in the keV regime. The verification of the generated entanglement by testing a single-particle version of Bell's inequality in an X-ray optics experimental setup is put forward.

Electrooptic PLZT ceramics devices for vision science applications

The present work reports on spectral transmission and scattering dependencies, the status of scattered light polarization for PLZT ceramics elements working in the electrically induced longitudinal light scattering mode. Experiments are done with the double optical integrated sphere technique. Several devices using the electrically controlled scattering effect are developed - eye occluders for studies of dynamics of visual and stereoscopic response, an artificial eye model to simulate optical transfer function of the eye with cataract of the lens.

Electrooptic PLZT Ceramics Devices for Vision Science Applications

The present work reports on spectral transmission and scattering dependencies, the status of scattered light polarization for PLZT ceramics elements working in the electrically induced longitudinal light scattering mode. Experiments are done with the double optical integrated sphere technique. Several devices using the electrically controlled scattering effect are developed - eye occluders for studies of dynamics of visual and stereoscopic response, an artificial eye model to simulate optical transfer function of the eye with cataract of the lens.

Anomalous polarization of Raman scattering by transverse and longitudinal phonons in porous doped GaAs

The Raman spectra of a porous doped GaAs(100) crystal were studied. It is established that emission in the plasma-phonon spectra of both the starting and porous crystals is highly polarized and is independent of the incident-radiation polarization. It is inferred that the contribution of the Froelich mechanism to the intensity of the plasma-phonon spectrum is predominant and that the effects of defects and multiple scattering on the scattered-light polarization in porous GaAs may be ignored. The cause for the violation of the selection rules in the spectrum of porous crystal is discussed.

Polarized light-scattering measurements of dielectric spheres upon a silicon surface

The polarization of light scattered into directions out of the plane of incidence by polystyrene latex spheres upon a silicon substrate was measured for p -polarized incident light. The experimental data show good agreement with theoretical predictions for three sizes of spheres. These results demonstrate that the polarization of light scattered by particles can be used to determine the size of particulate contaminants on silicon wafers. Theoretical models, based on successive degrees of approximation, indicate that the mean distance of a particle from the surface is the primary determinant of the scattered light polarization for small out-of-plane scattering angles.

Polarization in Light-scattering by Aerosol

Abstract The polarization of the light scattered by aerosol has been studied by the theoretical calculation based on the Mie scattering theory. The present calculation obtains the polarization of the light scattered by aerosol as a function of size parameter, i.e. x=2πr⁄λ, where r and λ are the radius of aerosol and the wavelength of the scattered light, respectively, for various refractive indexes. These results give the useful informations for the experimental study on the size-growth in aerosol formation by the measurement of the scattered light polarization. The characteristic of the scattered light intensity, which is usually used as a kind of concentration parameter in the study on aerosol formation, is also discussed.

Resonant Light Scattering by Single-Particle Electronic Excitations inn−GaAs

Resonant light scattering by single-particle excitations was observed in $n\ensuremath{-}\mathrm{GaAs}$ with incident photon energies near the ${E}_{0}+{\ensuremath{\Delta}}_{0}$ optical energy gap. We find that under extreme resonance conditions the spectra have two components with the scattered light polarization perpendicular and parallel to the incident light. These results are interpreted in terms of a random-phase-approximation theory.