Showing papers on "Circular polarization published in 2003"
TL;DR: An introduction to the topic of circular polarization is necessary to promote an understanding of the propagation aspects of modern communications system design and a simple laboratory-based project is described that requires the design, fabrication, and measurement of a crossed dipole antenna.
Abstract: Many modern satellite and terrestrial point-to-point communications systems use circular polarization (CP) wave propagation in order to maximize the polarization efficiency component of the link budget. Therefore, in an undergraduate electromagnetics syllabus, an introduction to the topic of circular polarization is necessary to promote an understanding of the propagation aspects of modern communications system design. Students new to the antennas and propagation discipline often have difficulty in grasping the concept of CP; therefore, in this paper, the essential aspects of this topic are reinforced by a tutorial description of CP in terms of wave propagation, antenna properties, and measurement techniques. A simple laboratory-based project is described that requires the design, fabrication, and measurement of a crossed dipole antenna. The measured input impedance and radiation patterns are correlated with theory to highlight the conditions necessary to support CP wave propagation. By combining basic electromagnetic concepts with a series of simple intuitive laboratory experiments, the students can more easily visualize, and hence understand, CP wave propagation and its use in communications systems design.
451 citations
TL;DR: In this paper, it was shown that the spin polarization of uniformly distributed electrons causes a directed motion of electrons in the plane of the QW. But the effect of spin polarization on the motion of the electrons was not investigated.
Abstract: Spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs) are reviewed. The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas. It is shown that in QWs belonging to one of the gyrotropic crystal classes a non-equilibrium spin polarization of uniformly distributed electrons causes a directed motion of electrons in the plane of the QW. A characteristic feature of this electric current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization-induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribution of spin-polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to reach a conclusion as regards the in-plane symmetry of QWs. The effect can also be utilized to develop fast detectors for determining the degree of circular polarization of a radiation beam. Furthermore, spin photocurrents under infrared excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.
336 citations
TL;DR: In this paper, a review of the lasing and photonic properties of periodic one-dimensional anisotropic structures with the symmetry of a double helix is presented, including self-organized cholesteric liquid crystals (CLCs) and sculptured thin films created by vapor deposition.
232 citations
TL;DR: A method is demonstrated that combines images obtained with linearly and circularly polarized light to produce a polarization-gated image that is free from surface reflections and does not require optically flat plates or matching fluid.
Abstract: A major drawback in polarization gating of light backscattered from tissue is that surface reflections dominate the image. An optically flat plate and matching fluid applied to the tissue surface, combined with off-axis detection, were previously used to address this problem. This approach is often inappropriate or inconvenient for practical use and more importantly can affect the tissue's optical properties. A method is demonstrated that combines images obtained with linearly and circularly polarized light to produce a polarization-gated image that is free from surface reflections and does not require optically flat plates or matching fluid.
172 citations
TL;DR: In this paper, the photonic densities of states of two normal light modes for propagation parallel to the helical axis were derived, taking into account multiple reflections due to the finite film thickness, and the influence of the degree of order of the dye's transition dipole moment on the emission characteristics.
Abstract: Due to the sinusoidal modulation of the dielectric properties along the helical axis, cholesteric liquid crystals exhibit a photonic stop band for circularly polarized light, which strongly affects the emission of fluorescent guest molecules. In this paper, we discuss the resulting changes in the emission spectrum. In an analytical treatment, we first derive the photonic densities of states of the two normal light modes for propagation parallel to the helical axis, taking into account multiple reflections due to the finite film thickness. Then we discuss the influence of the degree of order of the dye's transition dipole moment on the emission characteristics. Finally, we present experimental results, which show excellent quantitative agreement with our theoretical description.
158 citations
TL;DR: In this article, the authors present the polarization detections in DR 21(OH) from both the thermal dust emission at 1.3 mm and the CO J = 2? 1 line obtained with the Berkeley-Illinois-Maryland Association array.
Abstract: We present the polarization detections in DR 21(OH) from both the thermal dust emission at 1.3 mm and the CO J = 2 ? 1 line obtained with the Berkeley-Illinois-Maryland Association array. Our results are consistent with the prediction of the Goldreich-Kylafis effect that the CO polarization is either parallel or perpendicular to the magnetic field direction. The detection of the polarized CO emission is over a more extended region than the dust polarization, while the dust polarization provides an aid in resolving the ambiguity of the CO polarization. The combined results suggest that the magnetic field direction in DR 21(OH) is parallel to the CO polarization and therefore parallel to the major axis of DR 21(OH). The strong correlation between the CO and dust polarization suggests that magnetic fields are remarkably uniform throughout the envelope and the cores. The dispersion in polarization position angles implies a magnetic field strength in the plane of the sky of about 1 mG, compared to about 0.5 mG inferred for the line-of-sight field from previous CN Zeeman observations. Our CO data also show that both MM 1 and MM 2 power high-velocity outflows with v 25 km s-1 relative to the systemic velocity.
118 citations
TL;DR: In this article, the authors present a systematic, empirical design technique to obtain optimum broadband impedance, axial-ratio (AR) and gain bandwidths for a singly-fed electromagnetically coupled patch antenna for circular polarization.
Abstract: We present a systematic, empirical design technique to obtain optimum broadband impedance, axial-ratio (AR) and gain bandwidths for a singly-fed electromagnetically coupled patch antenna for circular polarization. Our investigation has also revealed tradeoffs amongst obtainable AR, impedance bandwidth and AR bandwidth. Using two design examples at different frequency bands and for different senses of circular polarization, we have demonstrated the effectiveness of the proposed knowledge-based tuning method. We have obtained at C-band measured values of impedance bandwidth (VSWR/spl les/2) equal to 43%, 3-dB AR bandwidth of 8%, AR of less than 0.3 dB and a mean gain level of 7 dB. For the Ku-band element, a 40% impedance bandwidth and a 17.3% of 3-dB AR bandwidth have been obtained with a peak gain of 7.2 dBic.
109 citations
TL;DR: In this article, a single parasitic patch for circular polarization excitation of the dielectric resonator antenna (DRA) is investigated, and the integral equations for the conformal-strip and parasitic-patch currents are formulated by matching the appropriate boundary conditions.
Abstract: The use of a single parasitic patch for circular polarization (CP) excitation of the dielectric resonator antenna (DRA) is investigated. For demonstration, the technique is applied to the conformal-strip fed hemispherical DRA, excited at the fundamental TE/sub 111/ mode. Using the Green's function approach, the integral equations for the conformal-strip and parasitic-patch currents are formulated by matching the appropriate boundary conditions. The equations are then solved using the method of moments (MoM). In using the MoM, both the rigorous and simplified current expansions are used for the parasitic patch, and their results are compared with each other. In each case, the impedance integrals are evaluated by virtue of newly obtained recurrence formulas and direct analytical integration. Hence, the results can be calculated very efficiently without the need for any numerical integration, which greatly facilitates the numerical implementation. The input impedance, axial ratio, and radiation patterns of the CP DRA are calculated, and the results are in good agreement with measurements.
106 citations
TL;DR: This work has applied a retrogressive solution: mechanical light modulation by rotating a linear polarizer with respect to a quarter wave plate continuously tuned by tilting to the operating wavelength to anomalously birefringent crystals of 1,8-dihydroxyanthraquinone.
Abstract: A microscope was constructed for imaging circular dichroism of heterogeneous anisotropic media. To avoid linear biases that are common with electronic circular polarization modulation, we chose a retrogressive solution: mechanical light modulation by rotating a linear polarizer with respect to a quarter wave plate continuously tuned by tilting to the operating wavelength. Our comparatively slow technique succeeds with near-perfect circular input and signal averaging using a CCD camera. We have applied the method to anomalously birefringent crystals of 1,8-dihydroxyanthraquinone that are shown to have intergrown mirror image domains, undetected by X-ray diffraction because the twinning complexity renders differences in anomalous dispersion, already small, unreliable. The origin of the anomalous birefringence and the assignment of the absolute configuration are discussed.
103 citations
TL;DR: Detailed, high-resolution experimental data confirm with high precision the elliptic-field topological sign rule, loop rules, and Stokes singularity relations introduced recently.
Abstract: Polarization singularities and elliptic stationary points (collectively, elliptic critical points) were measured experimentally via the complex Stokes field S1 + iS2, where S1 and S2 are Stokes parameters This new, easily implemented method yielded detailed, high-resolution experimental data for all elliptic critical points These data confirm with high precision the elliptic-field topological sign rule, loop rules, and Stokes singularity relations introduced recently
99 citations
TL;DR: In this article, the polarization states of the higher order waves do not depend on the polarization state of the incoming light and that they are fully characterized by the polarization grating vector.
Abstract: Polarization gratings are nondepolarizing polarization elements that alter the polarization state of the transmitted light in a periodic way, yielding a polarization-dependent diffraction. Using both the Jones and Stokes formalisms, we demonstrate that the polarization states of the higher order waves do not depend on the polarization state of the incoming light and that they are fully characterized by the polarization grating vector. We furnish a general model for polarization gratings that can be advantageously used for their design and show that a chain of three polarization gratings is a achromatic in-line polarimeter. In addition, we show that polarization gratings can be used as a tool to measure polarization mode dispersion.
TL;DR: In this paper, the resonant optical excitation of a trion with circularly polarized light was described, and how this trion permits the readout of a single electron spin through a recycling transition.
Abstract: We describe theoretically the resonant optical excitation of a trion with circularly polarized light and discuss how this trion permits the readout of a single electron spin through a recycling transition. Optical pumping through a combination of circularly polarized optical $\ensuremath{\pi}$ pulses with permanent or $\ensuremath{\pi}$-pulsed transverse magnetic fields suggests feasible protocols for spin initialization.
TL;DR: In this paper, the primordial anisotropies of the cosmic microwave background (CMB) are linearly polarized via Compton-scattering, and the contribution can potentially reach the level of total Stokes-U at low frequencies due to the cubic dependence on the wavelength.
TL;DR: In this paper, the vector correlation approach for the study of dissociative photoionization of linear molecules enables us to achieve a complete description of molecular photoionisation by performing a single experiment using only one state of circularly, or elliptically, polarized light.
Abstract: In this paper we demonstrate that the vector correlation approach for the study of dissociative photoionization (DPI) of linear molecules enables us to achieve a complete description of molecular photoionization by performing a single experiment using only one state of circularly, or elliptically, polarized light. This is illustrated by the derivation of the complex dipole matrix elements for the benchmark DPI reaction of the NO molecule, where (4)–1 inner-valence ionization is induced by left-handed circularly polarized synchrotron radiation at h= 23.65 eV. The importance of electronic correlation for this process is emphasized by comparing the experimental results with multichannel Schwinger configuration interaction calculations. The energy dependence of the transition matrix elements and that of the electronic correlation in the 25–40 eV energy range are illustrated by the calculations and compared with the present results and recent experimental studies at 40.8 eV.
TL;DR: In this article, a single-fed elliptic dielectric resonator antenna is designed for circular polarization and a coaxial probe is chosen with the proper parameters to achieve wideband matching and good circular polarization properties.
Abstract: A single-fed elliptic dielectric resonator antenna is designed for circular polarization. The feed is a coaxial probe chosen with the proper parameters to achieve wideband matching and good circular polarization properties. The analysis is performed numerically using WIPL-D. The single-fed DRA achieves 3.5% circular polarization bandwidth and 14% matching bandwidth. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 454–456, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10948
TL;DR: In this paper, the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top and side emission configuration was compared.
Abstract: Detection of the degree of circular polarization of the electroluminescence of a light-emitting diode fitted with a spin injecting contact (a spin-LED) allows for a direct determination of the spin polarization of the injected carriers. Here, we compare the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top- and side-emission configuration. In contrast with top emission, we cannot detect the electrical spin injection in side emission from analysing the degree of circular polarization of the electroluminescence. To reduce resonant optical pumping of quantum-well excitons in the side emission, we have analysed structures with mesa sizes as small as 1 micron.
TL;DR: In this paper, the authors compared the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top and side emission configurations.
Abstract: Detection of the degree of circular polarization of the electroluminescence of a light-emitting diode (LED) fitted with a spin injecting contact (a spin-LED) allows the direct determination of the spin polarization of the injected carriers. Here, we compare the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top- and side-emission configurations. In contrast to top emission, we cannot detect the electrical spin injection in side emission by analyzing the degree of circular polarization of the electroluminescence. To reduce resonant optical pumping of quantum-well excitons in side emission, we have analyzed structures with mesa sizes as small as 1 μm.
TL;DR: The theoretical analysis shows that the proposed apparatus exhibits unique feature which allows it to operate as a polarization-independent multiwavelength periodic filter with a good channel isolation and to make its channel wavelength switchable by varying effective birefringence of the polarization-diversity loop through the proper adjustment of the polarized controllers contained within the loop.
Abstract: In this paper a polarization-independent all-fiber multiwavelength-switchable filter based on a polarization-diversity loop configuration is newly proposed. The proposed apparatus consists of a polarization beam splitter, high birefringence fibers, and polarization controllers. Our theoretical analysis shows that the apparatus exhibits unique feature which allows it to operate as a polarization-independent multiwavelength periodic filter with a good channel isolation and to make its channel wavelength switchable by varying effective birefringence of the polarization-diversity loop through the proper adjustment of the polarization controllers contained within the loop. Theoretical prediction was experimentally verified.
Patent•
19 Dec 2003TL;DR: In this paper, a switchable stereoscopic display system, wherein the switchable display system can display two-dimensional and three-dimensional images, includes an organic light emitting diode (OLED) display device; electronics that rapidly updates individual OLEDs; and a linearly polarizer for the OLED display device.
Abstract: A switchable stereoscopic display system, wherein the switchable stereoscopic display system can display two-dimensional and three-dimensional images, includes: an organic light emitting diode (OLED) display device; Electronics that rapidly updates individual OLEDs; and a linearly polarizer for the OLED display device. Additionally, a circular polarizing layer changes light from linearly polarized light to circular polarized light. A polarization layer, on top of the circular polarization layer, switches a polarization direction of emitted light within the OLED display device. Other electronics switches the polarization direction within independent segments of the polarization layer. Refreshed OLEDs are synched with the independent segments of the polarization layer.
TL;DR: A novel method for forming linearly polarized axially symmetric beams with various polarization orders that is based on computer-generated space-variant subwavelength gratings is presented and a phase modification of a helical structure that results from the Pancharatnam-Berry phase is experimentally demonstrated.
Abstract: We present a novel method for forming linearly polarized axially symmetric beams with various polarization orders that is based on computer-generated space-variant subwavelength gratings. We introduce and experimentally demonstrate that our space-variant polarization state manipulations are accompanied by a phase modification of a helical structure that results from the Pancharatnam-Berry phase. We have verified the polarization properties of our gratings for laser radiation at 10.6-microm wavelength.
11 Feb 2003-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a helicity switching system was developed by means of selecting radiation from two helical undulators in synchrotron radiation experiments, where right and left circular photon beams were alternately supplied to the beamline using electron beam orbit bumps.
Abstract: Helicity switching of circularly polarized undulator radiation provides a valuable tool in synchrotron radiation experiments, particularly in the study of circular dichroism. At SPring-8, we have developed a helicity switching system by means of selecting radiation from two helical undulators. Right and left circular photon beams are alternately supplied to the beamline using electron beam orbit bumps. Instead of reversing the magnetic field applied to a sample, helicity switched light was used in magnetic circular dichroism measurements and the measuring time was reduced by 1 3 .
TL;DR: In this article, the carrier polarization-dependent optical matrix elements for InAs/GaAs self-assembled quantum dots (SAQDs) for electron and hole spin injection into a range of quantum dot sizes and shapes, and for arbitrary emission directions.
Abstract: A quantum dot spin light emitting diode provides a test of carrier spin injection into a qubit and a means for analyzing carrier spin injection and local spin polarization. Even with 100% spin-polarized carriers the emitted light may be only partially circularly polarized due to the geometry of the dot. We have calculated carrier polarization-dependent optical matrix elements for InAs/GaAs self-assembled quantum dots (SAQDs) for electron and hole spin injection into a range of quantum dot sizes and shapes, and for arbitrary emission directions. Calculations for typical SAQD geometries with emission along [110] show light that is only 5% circularly polarized for spin states that are 100% polarized along [110]. Measuring along the growth direction gives near unity conversion of spin to photon polarization and is the least sensitive to uncertainties in SAQD geometry.
TL;DR: In this paper, the sign of the photogalvanic effect can be changed by tuning the radiation frequency of circularly polarized light, which can be found to be a direct consequence of the lifting of the spin degeneracy due to k-linear terms in the Hamiltonian.
Abstract: We show that the sign of the circular photogalvanic effect can be changed by tuning the radiation frequency of circularly polarized light. Here resonant inversion of the photogalvanic effect has been observed for direct intersubband transition in n-type GaAs quantum well structures. This inversion of the photon helicity driven current is a direct consequence of the lifting of the spin degeneracy due to k-linear terms in the Hamiltonian in combination with energy and momentum conservation and optical selection rules.
TL;DR: In this paper, the polarization properties of monochromatic light beams are studied and it is shown that the electric and magnetic fields in an electromagnetic beam have different polarization properties in general.
Abstract: The polarization properties of monochromatic light beams are studied In contrast to the idealization of an electromagnetic plane wave, finite beams which are everywhere linearly polarized in the same direction do not exist Neither do beams which are everywhere circularly polarized in a fixed plane It is also shown that transversely finite beams cannot be purely transverse in both their electric and magnetic vectors, and that their electromagnetic energy travels at less than c The electric and magnetic fields in an electromagnetic beam have different polarization properties in general, but there exists a class of steady beams in which the electric and magnetic polarizations are the same (and in which energy density and energy flux are independent of time) Examples are given of exactly and approximately linearly polarized beams, and of approximately circularly polarized beams
TL;DR: It is shown that the standard model in the literature for self-focusing of circularly polarized beams can lead to completely wrong results, that circular polarization is stable during self- focusing, and that nonparaxiality and vectorial effects arrest collapse, leading instead to focusing-defocusing oscillations.
Abstract: We present a systematic study of propagation of circularly polarized beams in a Kerr medium. In contrast to previous studies, vectorial effects (i.e., coupling to the axial component of the electric field and the grad-div term) and nonparaxiality are not neglected in the derivation. This leads to a system of equations that takes into account nonparaxiality, vectorial effects, and coupling to the opposite circular component (i.e., the one rotating in the opposite direction). Using this system we show that the standard model in the literature for self-focusing of circularly polarized beams can lead to completely wrong results, that circular polarization is stable during self-focusing, and that nonparaxiality and vectorial effects arrest collapse, leading instead to focusing-defocusing oscillations. We also show that circularly polarized beams are much less likely to undergo multiple filamentation than linearly polarized beams.
TL;DR: This study reports on polymer liquid crystals with periodically oriented mesogenic side chains and demonstrates that the resulting two-dimensional polarization gratings multiplex-diffract the laser beam and convert the polarization state at the same time.
Abstract: We report on polymer liquid crystals with periodically oriented mesogenic side chains and demonstrate that the resulting two-dimensional polarization gratings multiplex-diffract the laser beam and convert the polarization state at the same time. Two-dimensional diffraction patterns with various kinds of polarization states can be successfully generated by designing a combination of one-dimensional polarization gratings. This study is a considerable advance towards the realization of highly functionalized passive optical devices that can control both the beam propagation direction and the polarization state.
TL;DR: In this article, the authors achieved depth-resolved polarization microscopy by measuring third-harmonic generation induced by a tightly focused circularly polarized beam, in which the birefringence compensates for the phase mismatch between the fundamental and the third harmonic induced by dispersion.
Abstract: We achieve depth-resolved polarization microscopy by measuring third-harmonic generation induced by a tightly focused circularly polarized beam. In crystals exhibiting strong birefringence this signal is dominated by positively phase-matched third-harmonic generation. This process occurs in only optically anisotropic media, in which the birefringence compensates for the phase mismatch between the fundamental and the third harmonic induced by dispersion. Both the intensity and the polarization of the emitted signal provide information on the local optical anisotropy. We demonstrate the technique by imaging biogenic crystals in sea urchin larval spicules.
01 Mar 2003
TL;DR: Carbon polarization-dependent optical matrix elements for InAs/GaAs self-assembled quantum dots (SAQDs) for electron and hole spin injection into a range of quantum dot sizes and shapes, and for arbitrary emission directions are calculated.
Abstract: A quantum dot spin light emitting diode provides a test of carrier spin injection into a qubit and a means for analyzing carrier spin injection and local spin polarization. Even with 100% spin-polarized carriers the emitted light may be only partially circularly polarized due to the geometry of the dot. We have calculated carrier polarization-dependent optical matrix elements for InAs/GaAs self-assembled quantum dots (SAQDs) for electron and hole spin injection into a range of quantum dot sizes and shapes, and for arbitrary emission directions. Calculations for typical SAQD geometries with emission along [110] show light that is only 5% circularly polarized for spin states that are 100% polarized along [110]. Measuring along the growth direction gives near unity conversion of spin to photon polarization and is the least sensitive to uncertainties in SAQD geometry.
TL;DR: In this article, the authors demonstrate the possibility to control the generation of high-order harmonics by a thin layer of graphite upon varying the polarization and intensity of the laser field and show that even for very large deviations from exact circular polarization (the elliptical polarization angle is $\ensuremath{\theta}=45\ifmmode^\circ\else\text degree\fi{}),$ the dynamical symmetry based selection rules
Abstract: We demonstrate the possibility to control the generation of high-order harmonics by a thin layer of graphite upon varying the polarization and intensity of the laser field. While for monochromatic linearly polarized laser fields all odd-order harmonics are emitted, we find that even for very large deviations from exact circular polarization (the elliptical polarization angle is $\ensuremath{\theta}=45\ifmmode^\circ\else\textdegree\fi{}),$ the dynamical symmetry based selection rules $\ensuremath{\Omega}=(6m\ifmmode\pm\else\textpm\fi{}1)\ensuremath{\omega},$ $m=1,2,3\dots{},$ where $\ensuremath{\omega}$ and $\ensuremath{\Omega}$ are the fundamental and harmonic frequencies [Phys. Rev. Lett 80, 3743, 1998], are valid. Our results show that the generation and control of high-order harmonics in thin layers of graphite by varying the polarization and intensity of an infrared laser field is feasible and should be observed in experiments.
18 Jul 2003
TL;DR: In this paper, the sign of the photogalvanic effect can be changed by tuning the radiation frequency of circularly polarized light, which is shown to be a direct consequence of the lifting of the spin degeneracy due to k-linear terms in the Hamiltonian in conjunction with energy and momentum conservation and optical selection rules.
Abstract: We show that the sign of the circular photogalvanic effect can be changed by tuning the radiation frequency of circularly polarized light. Here resonant inversion of the photogalvanic effect has been observed for direct
intersubband transition in n-type GaAs quantum well structures. This inversion of the photon helicity driven
current is a direct consequence of the lifting of the spin degeneracy due to k-linear terms in the Hamiltonian in
combination with energy and momentum conservation and optical selection rules.