Investigate Polarization Properties Research Articles

Polarization characteristics and transverse spin of Mie scattering.

Complicated polarization states in the near field of Mie scattering have aroused wide interest due to their broad potential applications. In this work, we investigated polarization properties, including polarization dimension, degree of nonregularity, and transverse electric-field spin, of scattering of a partially polarized plane wave by a dielectric nanosphere based on the rigorous Mie scattering theory. It is shown that with the decrease of the correlation coefficient, the polarization dimension and degree of nonregularity generally increase. In the limit of unpolarized incident light, a nearly-perfect nonregular polarization state (PN = 0.928) appears in the near field and the spin is transverse to the radial direction everywhere. The rich structure contained by the partially polarized scattered light offers an approach to manipulating the interaction between light and nanoparticles, which may lead to novel designs of nanoantenna, optical trap and sensing.

Mueller-matrix modeling of the architecture in the cuticle of the beetle Chrysina resplendens

Circular Bragg reflectors have the ability of reflecting the cohanded circular-polarization mode of the inherent helicoidal structures. Cuticles of some plants and beetles are examples of natural circular Bragg reflectors. In many cases, the period or pitch of the helicoidal structure shows spatial variation across the cuticle (pitch profile). Among scarab beetles, the special architecture in the cuticle of the Chrysina resplendens comprising a birefringent layer sandwiched between two helicoidal layers reflects both right- and left-handed circular-polarization states. In this work, the modeling of Mueller-matrix data is applied to investigate polarization properties of this exceptional structure by using pitch profile and optical functions reported in the literature. Reflectance spectra for circular-polarization states are explained in terms of the phase shift introduced by the birefringent layer in a phasor plot. The azimuth-dependent polarization properties are investigated at oblique incidence for unpolarized light.

Polarization properties of AlN (101̅0) and (112̅0) non-polar surfaces: maximally localized Wannier functions study

AlN (101̅0) and (112̅0) surfaces are usually considered to be non-polar facets. However, polarization may be induced in the surface due to the surface dangling bonds. In this work, using the average local dipole evaluated by maximally localized Wannier functions, we investigated polarization properties of these two surfaces layer-by-layer. It is found that a remarkable polarization which is more than eight times that of the bulk, is induced on these two surfaces. Moreover, we found that the polarization oscillates around the bulk value in the inner surface layers, and quickly approaches to the bulk value at a depth of four layers. Such polarization variation was further analyzed from the viewpoints of atomic rearrangement and charge transfer. Thus (101̅0) and (112̅0) surfaces are actually not completely non-polar facets, but rather non-polar bulk core combined with polar surface layers which would potentially affect the surface properties. The present study may provide a deeper understanding of the non-polar AlN surfaces.

Intravascular Polarimetry in Patients With Coronary Artery Disease

ObjectivesThe aims of this first-in-human pilot study of intravascular polarimetry were to investigate polarization properties of coronary plaques in patients and to examine the relationship of these features with established structural characteristics available to conventional optical frequency domain imaging (OFDI) and with clinical presentation. BackgroundPolarization-sensitive OFDI measures birefringence and depolarization of tissue together with conventional cross-sectional optical frequency domain images of subsurface microstructure. MethodsThirty patients undergoing polarization-sensitive OFDI (acute coronary syndrome, n = 12; stable angina pectoris, n = 18) participated in this study. Three hundred forty-two cross-sectional images evenly distributed along all imaged coronary arteries were classified into 1 of 7 plaque categories according to conventional OFDI. Polarization features averaged over the entire intimal area of each cross section were compared among plaque types and with structural parameters. Furthermore, the polarization properties in cross sections (n = 244) of the fibrous caps of acute coronary syndrome and stable angina pectoris culprit lesions were assessed and compared with structural features using a generalized linear model. ResultsThe median birefringence and depolarization showed statistically significant differences among plaque types (p < 0.001 for both, one-way analysis of variance). Depolarization differed significantly among individual plaque types (p < 0.05), except between normal arteries and fibrous plaques and between fibrofatty and fibrocalcified plaques. Caps of acute coronary syndrome lesions and ruptured caps exhibited lower birefringence than caps of stable angina pectoris lesions (p < 0.01). In addition to clinical presentation, cap birefringence was also associated with macrophage accumulation as assessed using normalized SD. ConclusionsIntravascular polarimetry provides quantitative metrics that help characterize coronary arterial tissues and may offer refined insight into coronary arterial atherosclerotic lesions in patients.

Repeatability Assessment of Intravascular Polarimetry in Patients.

Intravascular polarimetry with polarization sensitive optical frequency domain imaging (PS-OFDI) measures polarization properties of the vessel wall and offers characterization of coronary atherosclerotic lesions beyond the cross-sectional image of arterial microstructure available to conventional OFDI. A previous study of intravascular polarimetry in cadaveric human coronary arteries found that tissue birefringence and depolarization provide valuable insight into key features of atherosclerotic plaques. In addition to various tissue components, catheter and sample motion can also influence the polarization of near infrared light as used by PS-OFDI. This paper aimed to evaluate the robustness and repeatability of imaging tissue birefringence and depolarization in a clinical setting. 30 patients scheduled for percutaneous coronary intervention at the Erasmus Medical Center underwent repeated PS-OFDI pullback imaging, using commercial imaging catheters in combination with a custom-built PS-OFDI console. We identified 274 matching cross sections among the repeat pullbacks to evaluate the reproducibility of the conventional backscatter intensity, the birefringence, and the depolarization signals at each spatial location across the vessel wall. Bland-Altman analysis revealed best agreement for the birefringence measurements, followed by backscatter intensity, and depolarization, when limiting the analysis to areas of meaningful birefringence. Pearson correlation analysis confirmed highest correlation for birefringence (0.86), preceding backscatter intensity (0.83), and depolarization (0.78). Our results demonstrate that intravascular polarimetry generates robust maps of tissue birefringence and depolarization in a clinical setting. This outcome motivates the use of intravascular polarimetry for future clinical studies that investigate polarization properties of arterial atherosclerosis.

Polarization properties of cubic blue phases of a cholesteric liquid crystal

In this paper, we have experimentally investigated polarization properties of the blue phase of a cholesteric liquid crystal in polycrystalline cells with different alignment layers. Experiments were carried out by various temperatures and wavelengths within the spectral range covering Bragg reflection. It was conclusively demonstrated that the change of polarization state of transmitted light through polycrystalline BP-cell is mainly due to Bragg reflection, while optical activity is relatively small. Besides, the linear birefringence was not observed, as expected. It was shown that the ellipticity of the outgoing polarization state can change from almost linear (1.33%) to elliptic (7.33%), depending on sample orientation, with negligible changing of optical rotatory power (for BP I at 470 nm). The results indicate that also polycrystalline BPLC structure, although locally anisotropic, is macroscopically isotropic showing non-negligible optical activity only for resonant wavelengths, although being much lower than that in a typical cholesteric phase. It was also shown that different alignment layers in BP-cell may shift Bragg reflection spectral range, so influencing the outgoing polarization state for particular wavelength.

Water response to intense electric fields: A molecular dynamics study.

This paper investigated polarization properties of water molecules in close proximity to an ionic charge in the presence of external electric fields by using an approach based on simulations at the atomic level. We chose sodium and chloride ions in water as examples of dilute ionic solutions and used molecular dynamics simulations to systematically investigate the influence of an external static electric field on structural, dipolar, and polarization properties of water near charged ions. Results showed that a threshold electric field higher than 10(8) V/m is needed to affect water polarization and increase mean dipole moment of water molecules close to the ion. A similar threshold holds for water permittivity profiles, although a field 10× higher is needed to ensure that water permittivity is almost constant independently of the position close to the ion. Electric fields of such intensities can greatly enhance polarizability of water in hydration shells around ions.

Durability of a PEMFC Pt–Co cathode catalyst layer during voltage cycling tests under supersaturated humidity conditions

We examined the durability of a carbon-supported Pt-based Co alloy catalyst (Pt–Co/C) during voltage cycling tests under supersaturated humidity conditions to simulate events such as flooding. The voltage cycling tests were conducted from 0.4V to 1V for up to 50,000 cycles using 100% relative humidity (RH) hydrogen as the anode gas and 189% RH nitrogen as the cathode gas. We performed cyclic voltammetry (CV) to evaluate the electrochemical surface area (ECSA) and investigated polarization properties to evaluate the activity of Pt–Co/C. The ECSA of Pt–Co/C decreased more slowly than that of a platinum catalyst (Pt/C) during tests (percentages of initial ECSA were 62% and 37% for Pt–Co/C and Pt/C, respectively), either because (1) initial Pt–Co/C was not dispersed unlike Pt/C, or (2) Pt/C exhibited stronger resistance to agglomeration than Pt–Co/C. We concluded that Pt–Co/C exhibited high oxygen reduction reaction (ORR) activity and durability during voltage cycling tests because the mass activity of Pt–Co/C was about twice that of Pt/C throughout the 50,000 cycles. Electrocatalytic specific activities of Pt–Co/C were constant and about twice those of Pt/C for 4000–50,000 cycles, indicating that alloying can increase intrinsic activity for up to 50,000 cycles.

Polarization properties of Mo/Si multilayers in the EUV range

We investigate polarization properties of two novel reflective Mo/Si multilayers (ML) in the EUV range using polarized synchrotron radiation at the BESSY-II storage ring facility. One of the Mo/Si ML is used as a retarder, the other one as an analyzer within the experimental setup of the BESSY soft-x-ray polarimeter. The analyzer multilayer is characterized by performing reflectivity measurements with s- and p-polarized light as a function of the incidence angle for different wavelengths. The characterization of the retarder multilayer consists of reflectivity measurements with s- and p-polarized light as a function of the wavelength for three different angles near normal incidence. In addition the phase retardance on reflection was determined for one angle of incidence as function of wavelength. Uncertainties of the phase retardance are estimated via the block bootstrap method. As an additional by-product of the ML characterization the Stokes parameters of the beamline could be determined. With the 8-axis BESSY polarimeter we have measured the complex reflection coefficients for the first time and established this ellipsometry technique as an additional probe to characterize multilayer optical elements.

Polarization properties of excitonic qubits in single self-assembled quantum dots

We investigate polarization properties of neutral exciton emission in single self-assembled InAs/GaAs quantum dots. The in-plane shape and strain anisotropy strongly couple the heavy and light hole states and lead to large optical anisotropy with non-orthogonal linearly polarized states misaligned with respect to the crystallographic axes. Owing to a waveguiding experimental configuration, luminescence polarization along the growth axis has been observed revealing the presence of shear components of the deformation tensor out of the growth plane. Resonant luminescence experiments allowed determining the oscillator strength ratio of the two exciton eigenstates. Valence band mixing governs this ratio and can be very different from dot to dot, however the polarization anisotropy axis is quite fixed inside a scanned area of one \mum^{2} and indicates that the in-plane deformation direction to which it is related has a correlation length of the order of magnitude of one \mum^{2}.

Transverse second-harmonic generation from disordered nonlinear crystals

Abstract We investigate the transverse second-harmonic generation in as grown strontium barium niobate (SBN) crystals with a random structure of anti-parallel ferroelectric domains. We consider both, single and counter-propagating pulse geometries. We investigate polarization properties of the second harmonic signal and discuss applications of this process for short pulses characterization.

Measurements of birefringence and its sensitivity to hydrostatic pressure and elongation in photonic bandgap hollow core fiber with residual core ellipticity

We investigated polarization properties of the photonic bandgap hollow core fiber operating in the first communication window. Using specially developed interferometric method, we measured dependence of phase and group modal birefringence upon wavelength in a wide spectral range. Our results show that the phase birefringence (Δn) is of the order of 10−5, depends parabolic like upon wavelength, and reaches minimum value in the vicinity of the bandgap center. The group modal birefringence (ΔN) decreases monotonically vs. wavelength from positive to negative value and crosses zero near the bandgap center. Due to high chromatic dispersion of the phase modal birefringence, the absolute value of ΔN is one order of magnitude higher than Δn at the bandgap boundaries. We also determined the susceptibility of the phase and the group modal birefringence to strain and hydrostatic pressure in the whole analyzed spectral range.

Polarization and decoherence in a two-component Bose$ndash$Einstein condensate

We theoretically investigate polarization properties of a two-component Bose-Einstein condensate (BEC) and influence of decoherence induced by environment on BEC polarization through introducing four BEC Stokes operators which are quantum analog of the classical Stokes parameters for a light field. BEC polarization states can be geometrically described by a Poincar\'{e} sphere defined by expectation values of BEC Stokes operators. Without decoherence, it is shown that nonlinear inter-atomic interactions in the BEC induce periodic polarization oscillations whose periods depend on the difference between self-interaction in each component and inter-component interaction strengths. In particular, when inter-atomic nonlinear self-interaction in each BEC component equals inter-component nonlinear interaction, Stokes vector associated with Stokes operators precesses around a fixed axis in the dynamic evolution of the BEC. The value of the processing frequency is determined by the strength of the linear coupling between two components of the BEC. When decoherence is involved, we find each component of the Stokes vector decays which implies that decoherence depolarizes the BEC.

A DEVICE TO MEASURE THE AMOUNT OF PLANE POLARIZED LIGHT IN LOW INTENSITY RADIATIONS AND TO MEASURE SMALL ROTATIONS OF THE PLANE OF POLARIZATION

To investigate polarization properties of radiations too weak to be handled with the common visual devices for the purpose, a photoelectric device is used. A nicol of good quality, with end faces perpendicular to the length is mounted on a caesium vacuum cell, and this, together with the working tube of a two tube bridge amplifier, placed in a brass container free to rotate about an axis passing through the center of the nicol. Control apparatus and the dummy tube and batteries are located in a stationary container, connections being made through a flexible shielded cable. The galvanometer deflection obtained is proportional to the intensity of the component of the radiation able to pass through the nicol. The percent of polarization has been measured with illuminations down to 10−5 foot-candles. When applied to rotation measurements, a rotation of the plane of polarization of one second of arc can be detected.