Polarization State Of Radiation Research Articles

Effect of polarization nonreciprocity in rotating fiber ring interferometers

The effect of polarization nonreciprocity in sensors of angular velocity of rotation—fiber ring interferometers (FRIs)—is considered for arbitrary polarization of eigenmodes of the single-mode optical fiber of an FRI loop and arbitrary polarization state of radiation at the FRI input. A new method for detecting the polarization nonreciprocity in an FRI is proposed. Numerical estimations are made.

Geometric phases in singlemode fiber lightguides and fiber ring interferometers

We consider various geometric phases (GPs) in singlemode fiber lightguides (SMFs) and in fiber ring interferometers (FRIs): the Pancharatnam phase stemming from the cyclic evolution of the polarization state of radiation (RP state) in SMF, the Rytov–Vladimirskii phase (RV phase) stemming from the Rytov effect (specifically, rotation of the polarization plane due to noncoplanar winding of SMFs), as well as the nonreciprocal phase difference of counterpropagating waves (NPDCW) and nonreciprocal geometric phase of counterpropagating waves (NGPCW), which are caused by polarization nonreciprocity (PN) in FRIs. We show that in the general case, the Pancharatnam phase for an arbitrary RP state is inconsistent with the real phase change of light fluctuations in mediathat possess not only circular but also linear birefringence. We show that the RV phase, having a geometric origin, can in principle be considered as a dynamic phase (DP). We also show that the NGPCW can be considered as an effect of the evolution of the RP state mapped on the Poincaré sphere in Ginzburg's orthogonal screw polarization modes (GSPMs) of SMFs in the FRI contour. We analyze a number of experiments in which geometric phases were detected in FRIs: changing the RV phase and Rytov's angle (RA) in response to change of the pitch of helicoidal winding of SMFs.

Excitons in monoclinic zinc diphosphide: The A-exciton series and Fano effect

The A-exciton series in the absorption spectra of β-ZnP2 monoclinic zinc diphosphide samples is investigated at different directions of the wave vector and different polarization states of radiation. It is shown that the oscillator strengths determined for the observed transitions are adequately described by the relationship Fn∝n−3 characteristic of S-type exciton states. The assumption is made that the A-exciton series is associated with the partially allowed dipole transitions to nS states of the orthoexciton with Γ2−(x) symmetry at ms=0. These states are mixed, to a first approximation, with nS states of the Γ2−(z) singlet exciton due to the spin-orbit 2 interaction and are split off by the long-range (nonanalytical) part of the exchange interaction. The Fano antiresonances arise in the absorption spectra at resonances of the A-exciton series when the radiation vector E (or the induction vector D) has a component along the crystallographic axis c. These antiresonances are induced by the configurational interaction of discrete exciton states of the A series with the continuum of the exciton-phonon spectrum due to indirect transitions to the 1S band of the singlet exciton with phonon emission.

Diffusion of photons with arbitrary state of polarization: the Monte Carlo code MCSHAPE

When X-rays penetrate in the matter, they interact with the atoms, producing secondary radiation that carries important information about the composition of the target. The polarization state is one of the properties of the incoming photons which changes as a consequence of the number and the type of the undergone interaction. Therefore, to study properly the atomic properties of a material, it is necessary to consider the evolution of the polarization state of radiation. It is presented MCSHAPE, a Monte Carlo code developed to describe the evolution of the polarization state of X-ray photons as a consequence of the multiple scattering collisions undergone during the diffusion into the sample. In order to study properly the transport of photons with an arbitrary state of polarization, the model adopted in this code is derived from the so called ‘vector’ transport equation [Radiative Transfer, Chapter 1, Section 15, Clarendon, Oxford, 1950; Nucl. Instr. and Meth. B 73 (1993) 341]. Using the Stokes parameters I, Q, U and V, having the dimension of an intensity and containing all the physical information about the polarization state, MCSHAPE simulates the full state of polarization of the photons at any given position, wavelength and solid angle.

Quantum interference of light polarization states via polarization quasiprobability functions

Quantum interference of polarization states of light radiation is investigated using a Wigner-type (W) polarization quasiprobability function. Two examples of light states, having the form of a macroscopically distinguishable superposition of either coherent or Fock states with alternatively excited polarization modes, are considered. Interference phenomena are shown to be connected with a specific entanglement of quantum states (due to their 'mirror-like' forms) and to be characterized by a universal 'four-photon' periodicity parameter. These effects are well exhibited via the negativity of the polarization W function and can be observed in direct polarization measurements.

Polarized directional reflectance from laurel and mullein leaves

The ability to perform polarimetric imaging throughout the vis- ible and infrared (IR) wavebands has improved considerably in the past decade. Systems now exist that enable measurements to be made of all four Stokes parameters arising from each pixel in the image. The ques- tion of whether polarimetric imaging offers an advantage over conven- tional imaging methods for discrimination of plant type in scenes of natu- ral vegetation remains to be answered. Although the size of a leaf may be below the spatial resolution of an imaging system, the polarimetric properties of individual leaves may affect the data observed from a tree or forest canopy. We report the results of measurements of the polarized hemispherical directional reflectance (HDR), which is related to the di- rectional emissivity, and bidirectional reflectance distribution function (BRDF) from two examples of leaves. To completely characterize the polarimetric properties of a leaf, and ultimately a leaf canopy, an exten- sive measurement of the polarized BRDF and HDR of individual leaves is required. This is necessary because of the large range of possible relative orientations of the illumination, leaf and observer, and the range of polarization states of incident radiation. We report a limited set of laboratory measurements designed to investigate whether any gross po- larimetric difference exist between two dissimilar types of plant leaves in the visible, near IR (NIR), and IR spectral wavebands. Laurel (prunus laurecatious) has a wax surface creating a gloss or glabrous appearance to the leaf. The surface of mullein (verbascum thapsus) is highly pubes- cent with a dense layer of hair over the adaxial surface, creating a highly diffuse surface reflectance. Significant differences are found between the two species of leaf in the measured polarized directional reflectance and emissivity. © 2002 Society of Photo-Optical Instrumentation Engineers.

TWO-BAND MAGNETO-OPTICAL ELEMENTS FOR SOFT X-RAY POLARIZATION ANALYSIS AT THE Fe, Co 2p AND Gd 3d EDGES

We present angle-, energy- and polarization-dependent magneto-optical properties of Gd/Fe and Gd/Co multilayers with periods of the order of 1 nm for the photon energy range of 700–1230 eV. In the vicinity of the 2p absorption edge of transition metals (TM) and the 3d edge of the rare earth elements (RE), the X ray magnetic circular dichroism (XMCD) was measured in transmission and the X ray resonant magnetic scattering (XRMS) was investigated in L-MOKE geometry. The magnetic state of Gd could be realized at room temperature. Based on these data a calibrated detector of the polarization state of synchrotron radiation has been developed.

Consideration on an undulator magnetic structure for polarization control

A magnetic structure composed of electromagnets and permanent magnets is proposed as an undulator to control the polarization state of synchrotron radiation. The horizontal field is produced by the permanent magnets and tuned by moving them along the undulator axis, while the vertical field is produced by the electromagnets and tuned by changing the coil current. The proposed device has two important degrees of freedom. One is that of the periodic length of the electromagnets and the other is that of the relative phase between the vertical and horizontal fields. Thanks to them, the proposed device works as various types of undulator to realize polarization control.

Explanation of the Motionless Electromagnetic Generator with O(3) Electrodynamics

Recently, Bearden el al. developed a device which is known as a motionless electromagnetic generator (MEG) and which produces a coefficient of performance (COP) far in excess of unity. The device has been independently replicated by Naudin. In this communication, the fundamental operational principle of the MEG is explained using a version of higher symmetry electrodynamics known as O(3) electrodynamics, which is based on the empirical existence of two circular polarization states of electromagnetic radiation, and which has been developed extensively in the literature. The theoretical explanation of the MEG with O(3) electrodynamics is straightforward: Magnetic energy is taken directly ex vacua and used to replenish the permanent magnets of the MEG device, which therefore produces a source of energy that, in theory, can be replenished indefinitely from the vacuum. Such a result is incomprehensible in U(1) Maxwell-Heaviside electrodynamics.

Polar and Longitudinal Magnetooptical Kerr Effects in Magnetic Film/Spacer/Magnetic Substrate System

The paper deals with the electromagnetic theory of longitudinal and normal incidence polar magnetooptical Kerr effects (MOKE) in sandwich structures consisting of a magnetic film on a thick magnetic substrate separated by a nonmagnetic spacer. These structures are employed in fundamental studies of magnetic exchange coupling, tunnel magnetoresistance, spin polarized current,etc., as well as in the design of the magnetoelectronic devices,e.g., magnetic random access memories. The results are expressed in terms of the Jones reflection matrix. This makes the analysis of the observed MOKE in various experimental set-ups easier. To first order in off-diagonal elements of the permittivity tensor, the analytical expressions approximate the results obtained using rigorous matrix formalisms with a little loss in accuracy, provided the magnetooptical effects quadratic in the offdiagonal elements are negligible. The total MOKE is expressed as a a sum of components originating from magnetic film and magnetic substrate, respectively. The components enter the analytical expressions with different phases and may be identified separately by a proper control of the polarization state and photon energy of the incident radiation, angle of incidence, nonmagnetic spacer thickness, and radiation wavelength. The formulae are derived without any restriction on the magnetic film thickness. However, for a rapid evaluation of the trends the MOKE response is also treated under the assumption that the thickness of the magnetic film is much smaller than the radiation wavelength.

Quadrupole radiation from terahertz dipole antennas

We report what is to our knowledge the first detailed investigation of the polarization state of radiation from lens-coupled terahertz dipole antennas. The radiation exhibits a weak but measurable component that is polarized orthogonally to the orientation of the emitter dipole. The angular radiation pattern of this cross-polarized emission reveals that it is quadrupolar, rather than dipolar, in nature. One can understand this result by taking into account the photocurrent flowing in the strip lines that feed the dipole antenna. A Fresnel-Kirchhoff scalar diffraction calculation is used for calculating the frequency-dependent angular distribution of the radiation pattern, providing satisfactory agreement with the measurements.

Excitons in monoclinic zinc diphosphide: Orthoexciton and polariton effects at n=1 resonance

Quantitative investigations of the hydrogen-like exciton B series in the absorption spectra of the β-ZnP2 crystal for various wave vector directions and polarization states of radiation are conducted. It is shown that the B spectrum constitutes a single orthoexciton series with S-type envelope functions, and low-energy components in doublet lines belong to the S-type for lines in the series with n≥3. Polariton effects are clearly manifested at the B n=1 exciton resonance, and Bouguer’s law is violated. The oscillator strength tensor components are determined for transitions to the exciton states of the B series, and the polariton parameters at the B n=1 exciton resonance are calculated.

Effect of ray refraction on evolution of the polarization state of radiation propagating in a nonuniform, birefringent, optically active and dichroic medium

The differential equation derived previously [J. Opt. Soc. Am. A 17, 95 (2000)] that describes the evolution of the polarization state of radiation propagating in a nonuniform, anisotropic, and dichroic medium is extended to include the effect of ray refraction.

New methods for determining the polarization state of vacuum ultraviolet radiation

Two new methods are proposed for determining the polarization of vacuum ultraviolet radiation which permit the determination of an arbitrary polarization mode for photons with energies of 10–100 eV. The essence of these methods is to create and detect a nonequilibrium population of the magnetic sublevels of atoms and molecules excited by the original VUV radiation and then determine the polarization of this radiation based on these measurements in accordance with known formulas.

Modulational method of eliminating the zero shift of a fiber ring interferometer induced by polarization nonreciprocity

A new method is proposed to eliminate the zero shift of a fiber ring interferometer induced by polarization nonreciprocity. This method is based on periodic modulation of the polarization state of nonmonochromatic radiation at the entrance to the interferometer ring system. Numerical estimates are given.

Quintessence and the Rest of the World: Suppressing Long-Range Interactions

A nearly massless, slowly rolling scalar field $\ensuremath{\varphi}$ may provide most of the energy density of the current Universe. One potential difficulty with this idea is that couplings to ordinary matter should lead to observable long-range forces and time dependence of the constants of nature. I explore the possibility that an approximate global symmetry serves to suppress such couplings even further. Such a symmetry would allow a coupling of $\ensuremath{\varphi}$ to the pseudoscalar ${F}_{\ensuremath{\mu}\ensuremath{\nu}}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{F}}^{\ensuremath{\mu}\ensuremath{\nu}}$ of electromagnetism, which would rotate the polarization state of radiation from distant sources. This effect is fairly well constrained, but it is conceivable that future improvements could lead to a detection of a cosmological scalar field.

Transmission of polarized infrared radiation through lamellar gratings on a silicon wafer

Studies of the zero angle of incidence transmission through lamellar gratings on silicon wafers were performed with polarized radiation in the spectral interval from 1.5 to 14 μm. All measured spectra consist of two parts: an oscillatory part at the wavelengths smaller than the grating period, and a nonoscillatory part at the wavelengths larger than the grating period. In some cases the transmittance in the oscillatory parts can be low, down to 4%, that demonstrates the effect of infrared “color separation.” We found experimentally that for gratings with periods larger than the maximum wavelength, the shape of the spectrum is polarization independent, while for gratings with periods smaller than the maximum wavelength the spectrum is very sensitive to the polarization of the radiation, especially in the nonoscillatory part. These results are consistent with the electromagnetic theory which states that at wavelengths smaller than the typical distance of index variations scalar approximation works, making no difference between the polarization states of radiation, whereas in the opposite case vector treatment is required. We developed a method of smoothing the interference fringes that emerge theoretically due to Fabry–Perot resonances in the substrate, but are not seen in the experiment due to the scattering of radiation by imperfections in the substrate. The method assumes this scattering to cause fluctuations of optical-path phase φo through the substrate. To calculate the apparent transmittance, the fringed one is specially filtered over φo. It is shown that for gratings with large periods the transmission spectra measured in our experimental conditions can be accounted for provided that one adopts a certain contribution of the ± first-order beam. The numerical simulations are in good agreement with experimental results.

Polarization characteristics of the “forbidden” second optical harmonic of femtosecond laser pulses in a bacteriorhodopsin solution

The generation of the second harmonic of femtosecond laser pulses in a bacteriorhodopsin solution has been experimentally studied for various wavelengths and polarization states of radiation at the fundamental frequency. The polarization properties of the effect are analyzed under various experimental conditions. The nature and properties of the signal are treated as the manifestation of a superposition of nonlinear optical effects of various orders (the second and the fourth). The second-order effects can have both an electric-dipole and a magnetic-dipole or electric-quadrupole character. In analyzing fourth-order processes, besides the direct electric-dipole contribution, the possibility of the participation of cascade processes at second-and third-order nonlinearities is also allowed.

Optimized External IR Reflection Spectroscopy for Quantitative Determination of Borophosphosilicate Glass Parameters

Infrared (IR) external reflection spectroscopy has been optimized for the quantitative determination of composition and film thickness of borophosphosilicate glass (BPSG) deposited on silicon wafer substrates. The precision of the partial least-squares calibrations for boron and phosphorus contents and thin-film thickness were measured as the cross-validated standard error of prediction statistic. The results showed that BPSG IR reflection spectra collected over a wide range of incident IR radiation angles (15°, 25°, 45°, and 60°) can be used for the simultaneous quantification of these three BPSG parameters. When high angles of incidence were employed, the measurement was found to be more sensitive to small errors in the angle of incidence. The polarization state of the incident IR radiation did not noticeably affect the prediction of the three calibrated BPSG parameters. The results achieved in this study provide guidelines for at-line process monitoring and quality control of BPSG thin films used in the fabrication of microelectronic devices. Index Headings: IR reflection; Multivariate calibration; Partial least-squares

Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation

Using multilayer linear polarizers, we have characterized the polarization state of radiation from bend-magnet beamline 9.3.2 at the Advanced Light Source as a function of vertical opening angle at photon energies of 367 and 722 eV. Both a fine slit and a coarse semi-aperture were stepped across the beam to accept different portions of the vertical radiation fan. Polarimetry yields the degree of linear polarization directly and the degree of circular polarization indirectly assuming an immeasurably small amount of unpolarized radiation based on the close agreement of the theoretical and experimental results for linear polarization. The results are in good agreement with theoretical calculations, with departures from theory resulting from uncertainty in the effective aperture of the measured beam. The narrow 0.037-mrad aperture on the orbit plane transmits a beam whose degree of linear polarization exceeds 0.99 at these energies. The wide semi-aperture blocking the beam from above and below transmits a beam with a maximum figure of merit, given by the square root of flux times the degree of circular polarization, when the aperture edge is on the orbit plane thus blocking only half of the total available flux.