Multiband Circular Polarizer Based on Fission Transmission of Linearly Polarized Wave for X-Band Applications

Directory of Open Access Journals (Sweden)

Farman Ali Mangi

2016-01-01

Full Text Available A multiband circular polarizer based on fission transmission of linearly polarized wave for x-band application is proposed, which is constructed of 2 × 2 metallic strips array. The linear-to-circular polarization conversion is obtained by decomposing the linearly incident x-polarized wave into two orthogonal vector components of equal amplitude and 90° phase difference between them. The innovative approach of “fission transmission of linear-to-circular polarized wave” is firstly introduced to obtain giant circular dichroism based on decomposition of orthogonal vector components through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer and two transmitted waves impinge on the upper printed strips layer to convert into four orthogonal vector components at the end of structure. This projection and transmission sequence of orthogonal components sustain the chain transmission of electromagnetic wave and can achieve giant circular dichroism. Theoretical analysis and microwave experiments are presented to validate the performance of the structure. The measured results are in good agreement with simulation results. In addition, the proposed circular polarizer exhibits the optimal performance with respect to the normal incidence. The right handed circularly polarized wave is emitted ranging from 10.08 GHz to 10.53 GHz and 10.78 GHz to 11.12 GHz, while the left handed circular polarized wave is excited at 10.54 GHz–10.70 GHz and 11.13 GHz–11.14 GHz, respectively.

Design and simulation of a novel circularly polarized antenna with polarization reconfigurable characteristics

Directory of Open Access Journals (Sweden)

Zhang Hai

2016-01-01

Full Text Available A novel circularly polarized antenna with polarization reconfigurable characteristics was designed using co-simulation of Ansoft HFSS and Designer software. It consists of a dual-polarized antenna and phase switching network which act as the feed network for the dual-polarized antenna. The phase switching network was designed based on a Wilkinson power divider, where the output port was connected with SPDT to form a switching network. By controlling the SPDT state-off / on, the phase difference of the two ports could be alternated, which generated the orthogonal modes between the two ports of dual-polarized antenna. So that Left-hand circular polarization (LHCP and Right-hand circular polarization (RHCP could be achieved. The simulation shown that reflection coefficient was less than -12 dB and the axial ratio was below 3 dB between 1.8 GHz and 2.4 GHz with polarization reconfigurable characteristics.

Generation of circular polarization of the cosmic microwave background

International Nuclear Information System (INIS)

Alexander, Stephon; Ochoa, Joseph; Kosowsky, Arthur

2009-01-01

The standard cosmological model, which includes only Compton scattering photon interactions at energy scales near recombination, results in zero primordial circular polarization of the cosmic microwave background. In this paper we consider a particular renormalizable and gauge-invariant standard model extension coupling photons to an external vector field via a Chern-Simons term, which arises as a radiative correction if gravitational torsion couples to fermions. We compute the transport equations for polarized photons from a Boltzmann-like equation, showing that such a coupling will source circular polarization of the microwave background. For the particular coupling considered here, the circular polarization effect is always negligible compared to the rotation of the linear polarization orientation, also derived using the same formalism. We note the possibility that limits on microwave background circular polarization may probe other photon interactions and related fundamental effects such as violations of Lorentz invariance.

Molecular photoelectron holography with circularly polarized laser pulses.

Science.gov (United States)

Yang, Weifeng; Sheng, Zhihao; Feng, Xingpan; Wu, Miaoli; Chen, Zhangjin; Song, Xiaohong

2014-02-10

We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.

Molecular electron recollision dynamics in intense circularly polarized laser pulses

Science.gov (United States)

Bandrauk, André D.; Yuan, Kai-Jun

2018-04-01

Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

A New Limit on CMB Circular Polarization from SPIDER

Science.gov (United States)

Nagy, J. M.; Ade, P. A. R.; Amiri, M.; Benton, S. J.; Bergman, A. S.; Bihary, R.; Bock, J. J.; Bond, J. R.; Bryan, S. A.; Chiang, H. C.; Contaldi, C. R.; Doré, O.; Duivenvoorden, A. J.; Eriksen, H. K.; Farhang, M.; Filippini, J. P.; Fissel, L. M.; Fraisse, A. A.; Freese, K.; Galloway, M.; Gambrel, A. E.; Gandilo, N. N.; Ganga, K.; Gudmundsson, J. E.; Halpern, M.; Hartley, J.; Hasselfield, M.; Hilton, G.; Holmes, W.; Hristov, V. V.; Huang, Z.; Irwin, K. D.; Jones, W. C.; Kuo, C. L.; Kermish, Z. D.; Li, S.; Mason, P. V.; Megerian, K.; Moncelsi, L.; Morford, T. A.; Netterfield, C. B.; Nolta, M.; Padilla, I. L.; Racine, B.; Rahlin, A. S.; Reintsema, C.; Ruhl, J. E.; Runyan, M. C.; Ruud, T. M.; Shariff, J. A.; Soler, J. D.; Song, X.; Trangsrud, A.; Tucker, C.; Tucker, R. S.; Turner, A. D.; Van Der List, J. F.; Weber, A. C.; Wehus, I. K.; Wiebe, D. V.; Young, E. Y.

2017-08-01

We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of Spider, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from Spider's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33< {\\ell }< 307. No other limits exist over this full range of angular scales, and Spider improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on {\\ell }({\\ell }+1){C}{\\ell }{VV}/(2π ) ranging from 141 to 255 μK2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

A New Limit on CMB Circular Polarization from SPIDER

Energy Technology Data Exchange (ETDEWEB)

Nagy, J. M.; Ade, P. A. R.; Amiri, M.; Benton, S. J.; Bergman, A. S.; Bihary, R.; Bock, J. J.; Bond, J. R.; Bryan, S. A.; Chiang, H. C.; Contaldi, C. R.; Doré, O.; Duivenvoorden, A. J.; Eriksen, H. K.; Farhang, M.; Filippini, J. P.; Fissel, L. M.; Fraisse, A. A.; Freese, K.; Galloway, M.; Gambrel, A. E.; Gandilo, N. N.; Ganga, K.; Gudmundsson, J. E.; Halpern, M.; Hartley, J.; Hasselfield, M.; Hilton, G.; Holmes, W.; Hristov, V. V.; Huang, Z.; Irwin, K. D.; Jones, W. C.; Kuo, C. L.; Kermish, Z. D.; Li, S.; Mason, P. V.; Megerian, K.; Moncelsi, L.; Morford, T. A.; Netterfield, C. B.; Nolta, M.; Padilla, I. L.; Racine, B.; Rahlin, A. S.; Reintsema, C.; Ruhl, J. E.; Runyan, M. C.; Ruud, T. M.; Shariff, J. A.; Soler, J. D.; Song, X.; Trangsrud, A.; Tucker, C.; Tucker, R. S.; Turner, A. D.; List, J. F. Van Der; Weber, A. C.; Wehus, I. K.; Wiebe, D. V.; Young, E. Y.

2017-08-01

We present a new upper limit on CMB circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for $B$-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the non-zero circular-to-linear polarization coupling of the HWP polarization modulators, data from SPIDER's 2015 Antarctic flight provides a constraint on Stokes $V$ at 95 and 150 GHz from $33<\\ell<307$. No other limits exist over this full range of angular scales, and SPIDER improves upon the previous limit by several orders of magnitude, providing 95% C.L. constraints on $\\ell (\\ell+1)C_{\\ell}^{VV}/(2\\pi)$ ranging from 141 $\\mu K ^2$ to 203 $\\mu K ^2$ at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain stronger constraints on circular polarization.

Inkjet printed circularly polarized antennas for GPS applications

KAUST Repository

Farooqui, Muhammad Fahad

2014-07-01

Two novel, inkjet printed circularly polarized antenna designs are presented for GPS applications. First antenna design comprises a planar monopole which has been made circularly polarized by the introduction of an L-shaped slit. The antenna shows a gain of 0.2 dBi at 1.575 GHz with 3-dB axial ratio bandwidth of 3.8%. The second antenna design comprises a modified monopole in the form of an inverted L and has been termed as circularly polarized inverted L antenna (CILA). The antenna shows a gain of -2 dBi at 1.575 GHz with 3-dB axial ratio bandwidth of 4.1%. Both the antenna designs are attractive for mobile applications.

Magnetic field generation by circularly polarized laser light and inertial plasma confinement in a miniature 'Magnetic Bottle' induced by circularly polarized laser light

International Nuclear Information System (INIS)

Kolka, E.

1993-07-01

A new concept of hot plasma confinement in a miniature magnetic bottle induced by circularly polarized laser light is suggested in this work. Magnetic fields generated by circularly polarized laser light may be of the order of megagauss. In this configuration the circularly polarized laser light is used to get confinement of a plasma contained in a good conductor vessel. The poloidal magnetic field induced by the circularly polarized laser and the efficiency of laser absorption by the plasma are calculated in this work. The confinement in this scheme is supported by the magnetic forces and the Lawson criterion for a DT plasma might be achieved for number density n=5*10 21 cm -3 and confinement time τ= 20 nsec. The laser and the plasma parameters required to get an energetic gain are calculated. (authors)

Multi-band circular polarizer based on a twisted triple split-ring resonator

International Nuclear Information System (INIS)

Wu Song; Huang Xiao-Jun; Yang He-Lin; Xiao Bo-Xun; Jin Yan

2014-01-01

A multi-band circular polarizer using a twisted triple split-ring resonator (TSRR) is presented and studied numerically and experimentally. At four distinct resonant frequencies, the incident linearly polarized wave can be transformed into left/right-handed circularly polarized waves. Numerical simulation results show that a y-polarized wave can be converted into a right-handed circularly polarized wave at 5.738 GHz and 9.218 GHz, while a left-handed circularly polarized wave is produced at 7.292 GHz and 10.118 GHz. The experimental results are in agreement with the numerical results. The surface current distributions are investigated to illustrate the polarization transformation mechanism. Furthermore, the influences of the structure parameters of the circular polarizer on transmission spectra are discussed as well. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Circular polarization observed in bioluminescence

NARCIS (Netherlands)

Wynberg, H.; Meijer, E.W.; Hummelen, J.C.; Dekkers, H.P.J.M.; Schippers, P.H.; Carlson, A.D.

1980-01-01

The left and right lanterns of live larvae of the fireflies Photuris lucicrescens and P. versicolor emitted circularly polarized light of opposite sense. A possible mechanism is discussed. [on SciFinder (R)

Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

Science.gov (United States)

Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

2018-04-01

The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

Femtosecond all-polarization-maintaining fiber laser operating at 1028 nm

DEFF Research Database (Denmark)

Olsson, R.K.; Andersen, T.V.; Leick, Lasse

2008-01-01

We present an effective solution for an all-polarization-maintaining modelocked femtosecond fiber laser operating at the central wavelength of 1028 nm. The laser is based on an Yb-doped active fiber. Modelocking is enabled by a semiconductor saturable absorber mirror, and the central wavelength i...... is enforced by a fiber Bragg grating. The laser is self-starting and demonstrates excellent stability gainst Q-switching. Pulse energies reach 13 nJ at 34 MHz repetition rate. External compression leads to near transform-limited pulses of 140 fs.......We present an effective solution for an all-polarization-maintaining modelocked femtosecond fiber laser operating at the central wavelength of 1028 nm. The laser is based on an Yb-doped active fiber. Modelocking is enabled by a semiconductor saturable absorber mirror, and the central wavelength...

Femtosecond pulse laser-induced self-organized nanostructures on the surface of ZnO crystal

International Nuclear Information System (INIS)

Zhong Minjian; Guo Guanglei; Yang Junyi; Ma Ninghua; Ye Guo; Ma Hongliang; Guo Xiaodong; Li Ruxin

2008-01-01

This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti:sapphire laser with a repetition rate of 250 kHz. For a linearly polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was promoted. The period of self-organization structures is about 180 nm. The grating orientation is adjusted by the laser polarization direction. A long range Bragg-like grating is formed by moving the sample at a speed of 10 μm/s. For a circularly polarized laser beam, uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal

Detecting spin polarization of nano-crystalline manganese doped zinc oxide thin film using circular polarized light

Energy Technology Data Exchange (ETDEWEB)

El-Sayed, H.M., E-mail: h_m_elsaid@hotmail.com

2016-02-01

The presence of spin polarization in Mn-doped ZnO thin film is very important for spintronic applications. Spin polarization was detected using simple method. This method depends on measuring the optical transmittance using circular polarized light in visible and near infra-red region. It was found that, there is a difference in the optical energy gap of the film for circular left and circular polarized light. For temperatures > 310 K the difference in energy gap is vanished. This result is confirmed by measuring the magnetic hysteresis of the film. This work introduces a promising method for measuring the ferromagnetism in diluted magnetic semiconductors. - Highlights: • Highly oriented c-axis of Mn-ZnO thin film doped with nitrogen is prepared. • The optical energy gap depends on the state of circularly polarized light. • The presence of spin polarization is confirmed using simple optical method. • Magnetic measurements are consistent with the results of the optical method.

A novel x-ray circularly polarized ranging method

Science.gov (United States)

Song, Shi-Bin; Xu, Lu-Ping; Zhang, Hua; Gao, Na; Shen, Yang-He

2015-05-01

Range measurement has found multiple applications in deep space missions. With more and further deep space exploration activities happening now and in the future, the requirement for range measurement has risen. In view of the future ranging requirement, a novel x-ray polarized ranging method based on the circular polarization modulation is proposed, termed as x-ray circularly polarized ranging (XCPolR). XCPolR utilizes the circular polarization modulation to process x-ray signals and the ranging information is conveyed by the circular polarization states. As the circular polarization states present good stability in space propagation and x-ray detectors have light weight and low power consumption, XCPolR shows great potential in the long-distance range measurement and provides an option for future deep space ranging. In this paper, we present a detailed illustration of XCPolR. Firstly, the structure of the polarized ranging system is described and the signal models in the ranging process are established mathematically. Then, the main factors that affect the ranging accuracy, including the Doppler effect, the differential demodulation, and the correlation error, are analyzed theoretically. Finally, numerical simulation is carried out to evaluate the performance of XCPolR. Projects supported by the National Natural Science Foundation of China (Grant Nos. 61172138 and 61401340), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2013JQ8040), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130203120004), the Open Research Fund of the Academy of Satellite Application, China (Grant No. 2014 CXJJ-DH 12), the Xi’an Science and Technology Plan, China (Grant No. CXY1350(4)), the Fundamental Research Funds for the Central Universities, China (Grant Nos. 201413B, 201412B, and JB141303), and the Open Fund of Key Laboratory of Precision Navigation and Timing Technology, National Time Service Center, Chinese

Slotted Circularly Polarized Microstrip Antenna for RFID Application

Directory of Open Access Journals (Sweden)

S. Kumar

2017-12-01

Full Text Available A single layer coaxial fed rectangular microstrip slotted antenna for circular polarization (CP is proposed for radio frequency identification (RFID application. Two triangular shaped slots and one rectangular slot along the diagonal axis of a square patch have been embedded. Due to slotted structure along the diagonal axis and less surface area, good quality of circular polarization has been obtained with the reduction in the size of microstrip antenna by 4.04 %. Circular polarization radiation performance has been studied by size and angle variation of diagonally slotted structures. The experimental result found for 10-dB return loss is 44 MHz with 10MHz of 3dB Axial Ratio (AR bandwidth respectively at the resonant frequency 910 MHz. The overall proposed antenna size including the ground plane is 80 mm x 80 mm x 4.572 mm.

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

Energy Technology Data Exchange (ETDEWEB)

Kortright, J.B.; Rice, M.; Hussain, Z. [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

Growing interest in utilizing circular polarization prompted the design of bend-magnet beamline 9.3.2 at the Advanced Light Source, covering the 30-1500 eV spectral region, to include vertical aperturing capabilities for optimizing the collection of circular polarization above and below the orbit plane. After commissioning and early use of the beamline, a multilayer polarimeter was used to characterize the polarization state of the beam as a function of vertical aperture position. This report partially summarizes the polarimetry measurements and compares results with theoretical calculations intended to simulate experimental conditions.

Circular polarization observed in bioluminescence

NARCIS (Netherlands)

Wijnberg, Hans; Meijer, E.W.; Hummelen, J.C.; Dekkers, H.P.J.M.; Schippers, P.H.; Carlson, A.D.

1980-01-01

While investigating circular polarization in luminescence, and having found it in chemiluminescence, we have studied bioluminescence because it is such a widespread and dramatic natural phenomenon. We report here that left and right lanterns of live larvae of the fireflies, Photuris lucicrescens and

Full-Stokes polarimetry with circularly polarized feeds. Sources with stable linear and circular polarization in the GHz regime

Science.gov (United States)

Myserlis, I.; Angelakis, E.; Kraus, A.; Liontas, C. A.; Marchili, N.; Aller, M. F.; Aller, H. D.; Karamanavis, V.; Fuhrmann, L.; Krichbaum, T. P.; Zensus, J. A.

2018-01-01

We present an analysis pipeline that enables the recovery of reliable information for all four Stokes parameters with high accuracy. Its novelty relies on the effective treatment of the instrumental effects even before the computation of the Stokes parameters, contrary to conventionally used methods such as that based on the Müller matrix. For instance, instrumental linear polarization is corrected across the whole telescope beam and significant Stokes Q and U can be recovered even when the recorded signals are severely corrupted by instrumental effects. The accuracy we reach in terms of polarization degree is of the order of 0.1-0.2%. The polarization angles are determined with an accuracy of almost 1°. The presented methodology was applied to recover the linear and circular polarization of around 150 active galactic nuclei, which were monitored between July 2010 and April 2016 with the Effelsberg 100-m telescope at 4.85 GHz and 8.35 GHz with a median cadence of 1.2 months. The polarized emission of the Moon was used to calibrate the polarization angle measurements. Our analysis showed a small system-induced rotation of about 1° at both observing frequencies. Over the examined period, five sources have significant and stable linear polarization; three sources remain constantly linearly unpolarized; and a total of 11 sources have stable circular polarization degree mc, four of them with non-zero mc. We also identify eight sources that maintain a stable polarization angle. All this is provided to the community for future polarization observations reference. We finally show that our analysis method is conceptually different from those traditionally used and performs better than the Müller matrix method. Although it has been developed for a system equipped with circularly polarized feeds, it can easily be generalized to systems with linearly polarized feeds as well. The data used to create Fig. C.1 are only available at the CDS via anonymous ftp to http

Circular polarization in a non-magnetic resonant tunneling device

Directory of Open Access Journals (Sweden)

Airey Robert

2011-01-01

Full Text Available Abstract We have investigated the polarization-resolved photoluminescence (PL in an asymmetric n-type GaAs/AlAs/GaAlAs resonant tunneling diode under magnetic field parallel to the tunnel current. The quantum well (QW PL presents strong circular polarization (values up to -70% at 19 T. The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affects the spin polarization of carriers in the QW. However, the circular polarization degree in the QW also depends on various other parameters, including the g-factors of the different layers, the density of carriers along the structure, and the Zeeman and Rashba effects.

Chiral retrieval method based on right circularly polarized and left circularly polarized waves

International Nuclear Information System (INIS)

Martín, Ernesto; Muñoz, Juan; Margineda, José; Molina-Cuberos, Gregorio J; García-Collado, Ángel J

2014-01-01

The free-wave characterization of metamaterials is usually carried out by illuminating a sample with a linearly polarized plane electromagnetic wave. At points before and after the sample, sensors are introduced to measure the transverse components of the field, in order to compute the reflection and transmission coefficients related with the co- and cross-polar field components. Based on this information, retrieval algorithms allow parameters like rotation angle, effective chirality and refraction index to be calculated. Here we propose to use the transmission signals under illumination with plane circularly polarized waves, without sensing the reflection signal, to calculate the chirality parameter and the rotation angle due to the electromagnetic activity of the material. This new method, which allows a simpler characterization of a chiral slab, is applied to the study of metamaterials composed of both periodic and random distributions of metallic structures with chiral symmetry. The experimental results are contrasted with simulations and alternative measurements obtained using linearly polarized waves. (paper)

Characterization of a microfocused circularly polarized x-ray probe

International Nuclear Information System (INIS)

Pollmann, J.; Srajer, G.; Maser, J.; Lang, J. C.; Nelson, C. S.; Venkataraman, C. T.; Isaacs, E. D.

2000-01-01

We report on the development of a circularly polarized x-ray microprobe in the intermediate energy range from 5 to 10 keV. In this experiment linearly polarized synchrotron radiation was circularly polarized by means of a Bragg-diffracting diamond phase retarder and subsequently focused down to a spot size of about 4x2 μm 2 by a Fresnel zone plate. The properties of the microprobe were characterized, and the technique was applied to the two-dimensional mapping of magnetic domains in HoFe 2 . (c) 2000 American Institute of Physics

Electrically small circularly polarized spherical antenna with air core

DEFF Research Database (Denmark)

Kim, O. S.

2013-01-01

An electrically small circularly polarized self-resonant spherical antenna with air core is presented. The antenna is a modified multiarm spherical helix exciting TM10 and TE10 spherical modes with equal radiated power, and thus yielding perfect circular polarization over the entire far......-field sphere (except the polar regions, where the radiation is low). The self-resonance is achieved by exciting higher-order TM modes, which provide the necessary electric stored energy in the near-field, while contributing negligibly to the far-field radiation of the antenna. The antenna has electrical size...

Negative circular polarization as a universal property of quantum dots

International Nuclear Information System (INIS)

Taylor, Matthew W.; Spencer, Peter; Murray, Ray

2015-01-01

This paper shows that negative circular polarization, a spin flip of polarized carriers resulting in emission of opposite helicity, can be observed in undoped, n-doped, and p-doped InAs/GaAs quantum dots. These results contradict the usual interpretation of the effect. We show using power dependent and time resolved spectroscopy that the generation of negative circular polarization correlates with excited state emission. Furthermore, a longer spin lifetime of negatively polarized excitons is observed where emission is largely ground state in character

Polarization control of high order harmonics in the EUV photon energy range.

Science.gov (United States)

Vodungbo, Boris; Barszczak Sardinha, Anna; Gautier, Julien; Lambert, Guillaume; Valentin, Constance; Lozano, Magali; Iaquaniello, Grégory; Delmotte, Franck; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

2011-02-28

We report the generation of circularly polarized high order harmonics in the extreme ultraviolet range (18-27 nm) from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. To circularly polarize the initially linearly polarized harmonics we have implemented a four-reflector phase-shifter. Fully circularly polarized radiation has been obtained with an efficiency of a few percents, thus being significantly more efficient than currently demonstrated direct generation of elliptically polarized harmonics. This demonstration opens up new experimental capabilities based on high order harmonics, for example, in biology and materials science. The inherent femtosecond time resolution of high order harmonic generating table top laser sources renders these an ideal tool for the investigation of ultrafast magnetization dynamics now that the magnetic circular dichroism at the absorption M-edges of transition metals can be exploited.

Circularly polarized antennas

CERN Document Server

Gao, Steven; Zhu, Fuguo

2013-01-01

This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

Magnetic x-ray circular dichroism in spin-polarized photoelectron diffraction

International Nuclear Information System (INIS)

Waddill, G.D.; Tobin, J.G.

1994-01-01

The first structural determination with spin-polarized, energy-dependent photoelectron diffraction using circularly-polarized x-rays is reported for Fe films on Cu(001). Circularly-polarized x-rays produced spin-polarized photoelectrons from the Fe 2p doublet, and intensity asymmetries in the 2p 3/2 level are observed. Fully spin-specific multiple scattering calculations reproduced the experimentally-determined energy and angular dependences. A new analytical procedure which focuses upon intensity variations due to spin-dependent diffraction is introduced. A sensitivity to local geometric and magnetic structure is demonstrated

Polarization variablity among Wolf-Rayet stars. IV. A complete lack of circular polarization in the optical continuum

International Nuclear Information System (INIS)

Robert, C.; Moffat, A.F.J.

1989-01-01

Quasi-simultaneous blue and red, broadband optical monitoring in linear and circular polarization and in intensity has been carried out over an interval of three weeks for several Wolf-Rayet stars that show relatively large Delta P variations in linear polarization. No significant varying Delta V component of circular polarization is detected in any of these stars. The lower upper limit Delta V/Delta P implies that the intrinsic linearly polarized light which does vary cannot be produced by electrons gyrating in a magnetic field, unless they are ultrarelativistic - a rather unlikely situation. The low mean circular polarization typically observed is probably interstellar in origin. Lack of periodicity in the observed variations of linear polarization implies that even weak magnetic field loops are unlikely to be involved in confining pockets of wind plasma. The observed linear polarization variations are related mainly to electron scattering. 25 refs

Bragg transmission phase plates for the production of circularly polarized x-rays

International Nuclear Information System (INIS)

Lang, J.C.; Srajer, G.

1994-01-01

A thin-crystal Si (400) Bragg transmission x-ray phase plate has been constructed for the production of 5 to 12 keV circularly polarized x-rays. Using multiple beam diffraction from a GaAs crystal, a direct measurement of the degree of circular polarization as a function of off-Bragg position was made. These measurements indicated nearly complete circular polarization (|P c | ≥ 0.95) and full helicity reversal on opposite sides of the rocking curve

Circular dichroism measurements at an x-ray free-electron laser with polarization control

Energy Technology Data Exchange (ETDEWEB)

Hartmann, G.; Shevchuk, I.; Walter, P.; Viefhaus, J. [Deutsches Elektronen-Synchrotron, Notkestraße 85, 22607 Hamburg (Germany); Lindahl, A. O. [PULSE at Stanford, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Knie, A. [Institut für Physik, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Glownia, J. M.; Helml, W.; Huang, Z.; Marinelli, A.; Nuhn, H.-D.; Moeller, S.; Coffee, R. N.; Ilchen, M., E-mail: markus.ilchen@xfel.eu [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Buck, J.; Galler, A.; Liu, J. [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); and others

2016-08-15

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O{sub 2} 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

Circular dichroism measurements at an x-ray free-electron laser with polarization control

Science.gov (United States)

Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

2016-08-01

A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

Interrogation of orbital structure by elliptically polarized intense femtosecond laser pulses

DEFF Research Database (Denmark)

Abu-Samha, Mahmoud; Madsen, Lars Bojer

2011-01-01

We solve the three-dimensional time-dependent Schrödinger equation and present investigations of the imprint of the orbital angular node in photoelectron momentum distributions of an aligned atomic p-type orbital following ionization by an intense elliptically polarized laser pulse of femtosecond...

Control of periodic surface structures on silicon by combined temporal and polarization shaping of femtosecond laser pulses

Science.gov (United States)

Fraggelakis, F.; Stratakis, E.; Loukakos, P. A.

2018-06-01

We demonstrate the capability to exercise advanced control on the laser-induced periodic surface structures (LIPSS) on silicon by combining the effect of temporal shaping, via tuning the interpulse temporal delay between double femtosecond laser pulses, along with the independent manipulation of the polarization state of each of the individual pulses. For this, cross-polarized (CP) as well as counter-rotating (CR) double circularly polarized pulses have been utilized. The pulse duration was 40 fs and the central wavelength of 790 nm. The linearly polarized double pulses are generated by a modified Michelson interferometer allowing the temporal delay between the pulses to vary from Δτ = -80 ps to Δτ = +80 ps with an accuracy of 0.2 fs. We show the significance of fluence balance between the two pulse components and its interplay with the interpulse delay and with the order of arrival of the individually polarized pulse components of the double pulse sequence on the final surface morphology. For the case of CR pulses we found that when the pulses are temporally well separated the surface morphology attains no axial symmetry. But strikingly, when the two CP pulses temporally overlap, we demonstrate, for the first time in our knowledge, the detrimental effect that the phase delay has on the ripple orientation. Our results provide new insight showing that temporal pulse shaping in combination with polarization control gives a powerful tool for drastically controlling the surface nanostructure morphology.

Circularly polarized light emission in scanning tunneling microscopy of magnetic systems

International Nuclear Information System (INIS)

Apell, S.P.; Penn, D.R.; Johansson, P.

2000-01-01

Light is produced when a scanning tunneling microscope is used to probe a metal surface. Recent experiments on cobalt utilizing a tungsten tip found that the light is circularly polarized; the sense of circular polarization depends on the direction of the sample magnetization, and the degree of polarization is of order 10%. This raises the possibility of constructing a magnetic microscope with very good spatial resolution. We present a theory of this effect for iron and cobalt and find a degree of polarization of order 0.1%. This is in disagreement with the experiments on cobalt as well as previous theoretical work which found order of magnitude agreement with the experimental results. However, a recent experiment on iron showed 0.0±2%. We predict that the use of a silver tip would increase the degree of circular polarization for a range of photon energies

Modeling radio circular polarization in the Crab nebula

Science.gov (United States)

Bucciantini, N.; Olmi, B.

2018-03-01

In this paper, we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extragalactic ones. Its spectral and polarization properties allow us to infer key information on the particles distribution function and magnetic field geometry. In recent years, our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric techniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

Linearly and circularly polarized laser photoinduced molecular order in azo dye doped polymer films

Directory of Open Access Journals (Sweden)

Saad Bendaoud

2017-01-01

Full Text Available Photo-induced behavior of Azo Disperse one (AZD1 doped Poly(Methyl MethAcrylate (PMMA using both linear and circular polarized light is studied. The anisotropy is not erased by the circular polarization light. The circular polarization light combined with relatively long lifetime of the cis state in azo dye doped polymers activate all transverse directions of the angular hole burning through the spot in the film inducing anisotropy. Under circular polarized light, there is no orientation perpendicularly to the helex described by the rotating electric field vector, trans molecules reorients in the propagation direction of the pump beam. The polarization state of the probe beam after propagation through the pumped spot depends strongly on the angle of incidence of both pump and probe beams on the input face. In the case where circular polarized pump and probe beams are under the same angle of incidence, the probe beam “sees” anisotropic film as if it is isotropic. Results of this work shows the possibility to reorient azobenzene-type molecules in two orthogonal directions using alternately linearly and circularly polarized beams.

Circularly polarized luminescence of syndiotactic polystyrene

Science.gov (United States)

Rizzo, Paola; Abbate, Sergio; Longhi, Giovanna; Guerra, Gaetano

2017-11-01

Syndiotactic polystyrene (s-PS) films, when crystallized from the amorphous state by temporary sorption of non-racemic guest molecules (like carvone) not only exhibit unusually high optical activity, both in the UV-Visible and Infrared ranges, but also present circularly polarized luminescence (CPL) with high dissymmetry ratios (g = ΔI/I values in the range 0.02-0.03). Experimental evidences provide support, rather than to the usual molecular circular dichroism, to a supramolecular chiral optical response being extrinsic to the site of photon absorption and emission, possibly associated with a helical morphology of s-PS crystallites.

Circular polarization measurements with a Ge(Li) detector

DEFF Research Database (Denmark)

Kopecký, J.; Warming, Inge Elisabeth

1969-01-01

This paper presents the results obtained in measurements of the degree of circular polarization of gamma transitions to bound states of 33S, 36Cl, 49Ti, 56Mn, 57Fe, 60Co and 64Cu following the capture of polarized thermal neutrons. Spin values have been determined on the basis of these results....

Circularly polarized near-field optical mapping of spin-resolved quantum Hall chiral edge states.

Science.gov (United States)

Mamyouda, Syuhei; Ito, Hironori; Shibata, Yusuke; Kashiwaya, Satoshi; Yamaguchi, Masumi; Akazaki, Tatsushi; Tamura, Hiroyuki; Ootuka, Youiti; Nomura, Shintaro

2015-04-08

We have successfully developed a circularly polarized near-field scanning optical microscope (NSOM) that enables us to irradiate circularly polarized light with spatial resolution below the diffraction limit. As a demonstration, we perform real-space mapping of the quantum Hall chiral edge states near the edge of a Hall-bar structure by injecting spin polarized electrons optically at low temperature. The obtained real-space mappings show that spin-polarized electrons are injected optically to the two-dimensional electron layer. Our general method to locally inject spins using a circularly polarized NSOM should be broadly applicable to characterize a variety of nanomaterials and nanostructures.

Preliminary Design of a Femtosecond Oscilloscope

CERN Document Server

Gazazyan, Edmond D; Kalantaryan, Davit K; Laziev, Edouard; Margaryan, Amour

2005-01-01

The calculations on motion of electrons in a finite length electromagnetic field of linearly and circularly polarized laser beams have shown that one can use the transversal deflection of electrons on a screen at a certain distance after the interaction region for the measurement of the length and longitudinal particle distribution of femtosecond bunches. In this work the construction and preliminary parameters of various parts of a device that may be called femtosecond oscilloscope are considered. The influence of various factors, such as the energy spread and size of the electron bunches, are taken into account. For CO2 laser intensity 1016 W/cm2 and field free drift length 1m the deflection is 5.3 and 0.06 cm, while the few centimeters long interaction length between 2 mirrors requires assembling accuracy 6 mm and 1.3 micron for 20 MeV to 50 keV, respectively.

Circularly polarized infrared and visible sum-frequency-generation spectroscopy: Vibrational optical activity measurement

International Nuclear Information System (INIS)

Cheon, Sangheon; Cho, Minhaeng

2005-01-01

Vibrational optical activity spectroscopies utilizing either circularly polarized ir or circularly polarized visible beams were theoretically investigated by considering the infrared and visible sum-frequency-generation (IV-SFG) schemes. In addition to the purely electric dipole-allowed chiral component of the IV-SFG susceptibility, the polarizability-electric quadrupole hyperpolarizability term also contributes to the vibrationally resonant IV-SFG susceptibility. The circular-intensity-difference signal is shown to be determined by the interferences between the all-electric dipole-allowed chiral component and the polarizability-electric-dipole or electric-dipole-electric-quadrupole Raman optical activity tensor components. The circularly polarized SFG methods are shown to be potentially useful coherent spectroscopic tools for determining absolute configurations of chiral molecules in condensed phases

A New Kind of Circular Polarization Leaky-Wave Antenna Based on Substrate Integrated Waveguide

Directory of Open Access Journals (Sweden)

Chong Zhang

2015-01-01

Full Text Available A new kind of circular polarization leaky-wave antenna with N-shaped slots cut in the upper side of substrate integrated waveguide (SIW is investigated and presented. The radiation pattern and polarization axial ratio of the leaky-wave antenna are studied. The results show that the width of N-shaped slots has significant effect on the circular polarization property of the antenna. By properly choosing structural parameters, the SIW based leaky-wave antenna can realize circular polarization with excellent axial ratio in 8 GHz satellite band.

Investigating circular patterns in linear polarization observations of Venus

NARCIS (Netherlands)

Mahapatra, G.; Stam, D.M.; Rossi, L.C.G.; Rodenhuis, M.; Snik, Frans; Keller, C.U.

2017-01-01

In this work, we analyse linear polarization data of the planet at a distance, obtained with the Extreme Polarimeter (ExPo) on the William Herschel Telescope
on La Palma. These spatially resolved, high-accuracy polarization observations of Venus show faint circular patterns centered on the

A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

DEFF Research Database (Denmark)

Kaminski, Maciej; Cukras, Janusz; Pecul, Magdalena

2015-01-01

We present a computational methodology to calculate the intensity of circular dichroism (CD) in spinforbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet–singlet transitions in chiral compounds. The protocol is based...

Chiral Plasmonic Nanostructures Fabricated by Circularly Polarized Light.

Science.gov (United States)

Saito, Koichiro; Tatsuma, Tetsu

2018-05-09

The chirality of materials results in a wide variety of advanced technologies including image display, data storage, light management including negative refraction, and enantioselective catalysis and sensing. Here, we introduce chirality to plasmonic nanostructures by using circularly polarized light as the sole chiral source for the first time. Gold nanocuboids as precursors on a semiconductor were irradiated with circularly polarized light to localize electric fields at specific corners of the cuboids depending on the handedness of light and deposited dielectric moieties as electron oscillation boosters by the localized electric field. Thus, plasmonic nanostructures with high chirality were developed. The present bottom-up method would allow the large-scale and cost-effective fabrication of chiral materials and further applications to functional materials and devices.

Analysis of the multipactor effect in circular waveguides excited by two orthogonal polarization waves

Energy Technology Data Exchange (ETDEWEB)

Pérez, A. M.; Boria, V. E. [Departamento de Comunicaciones-iTEAM, Universidad Politécnica de Valencia Camino de Vera s/n, 46022 Valencia (Spain); Gimeno, B. [Departamento de Física Aplicada y Electromagnetismo-ICMUV, Universitat de València c/Dr. Moliner, 50, 46100 Valencia (Spain); Anza, S.; Vicente, C.; Gil, J. [Aurora Software and Testing S.L., Edificio de Desarrollo Empresarial 9B, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)

2014-08-15

Circular waveguides, either employed as resonant cavities or as irises connecting adjacent guides, are widely present in many passive components used in different applications (i.e., particle accelerators and satellite subsystems). In this paper, we present the study of the multipactor effect in circular waveguides considering the coexistence of the two polarizations of the fundamental TE{sub 11} circular waveguide mode. For a better understanding of the problem, only low multipactor orders have been explored as a function of the polarization ellipse eccentricity. Special attention has been paid to the linear and circular polarizations, but other more general configurations have also been explored.

Analysis of the multipactor effect in circular waveguides excited by two orthogonal polarization waves

International Nuclear Information System (INIS)

Pérez, A. M.; Boria, V. E.; Gimeno, B.; Anza, S.; Vicente, C.; Gil, J.

2014-01-01

Circular waveguides, either employed as resonant cavities or as irises connecting adjacent guides, are widely present in many passive components used in different applications (i.e., particle accelerators and satellite subsystems). In this paper, we present the study of the multipactor effect in circular waveguides considering the coexistence of the two polarizations of the fundamental TE 11 circular waveguide mode. For a better understanding of the problem, only low multipactor orders have been explored as a function of the polarization ellipse eccentricity. Special attention has been paid to the linear and circular polarizations, but other more general configurations have also been explored

Arbitrary helicity control of circularly polarized light from lateral-type spin-polarized light-emitting diodes at room temperature

Science.gov (United States)

Nishizawa, Nozomi; Aoyama, Masaki; Roca, Ronel C.; Nishibayashi, Kazuhiro; Munekata, Hiro

2018-05-01

We demonstrate arbitrary helicity control of circularly polarized light (CPL) emitted at room temperature from the cleaved side facet of a lateral-type spin-polarized light-emitting diode (spin-LED) with two ferromagnetic electrodes in an antiparallel magnetization configuration. Driving alternate currents through the two electrodes results in polarization switching of CPL with frequencies up to 100 kHz. Furthermore, tuning the current density ratio in the two electrodes enables manipulation of the degree of circular polarization. These results demonstrate arbitrary electrical control of polarization with high speed, which is required for the practical use of lateral-type spin-LEDs as monolithic CPL light sources.

Optimized fan-shaped chiral metamaterial as an ultrathin narrow-band circular polarizer at visible frequencies

Science.gov (United States)

He, Yizhuo; Wang, Xinghai; Ingram, Whitney; Ai, Bin; Zhao, Yiping

2018-04-01

Chiral metamaterials have the great ability to manipulate the circular polarizations of light, which can be utilized to build ultrathin circular polarizers. Here we build a narrow-band circular polarizer at visible frequencies based on plasmonic fan-shaped chiral nanostructures. In order to achieve the best optical performance, we systematically investigate how different fabrication factors affect the chiral optical response of the fan-shaped chiral nanostructures, including incident angle of vapor depositions, nanostructure thickness, and post-deposition annealing. The optimized fan-shaped nanostructures show two narrow bands for different circular polarizations with the maximum extinction ratios 7.5 and 6.9 located at wavelength 687 nm and 774 nm, respectively.

Linear Polarization, Circular Polarization, and Depolarization of Gamma-ray Bursts: A Simple Case of Jitter Radiation

Energy Technology Data Exchange (ETDEWEB)

Mao, Jirong; Wang, Jiancheng, E-mail: jirongmao@mail.ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, Yunnan Province (China)

2017-04-01

Linear and circular polarizations of gamma-ray bursts (GRBs) have been detected recently. We adopt a simplified model to investigate GRB polarization characteristics in this paper. A compressed two-dimensional turbulent slab containing stochastic magnetic fields is considered, and jitter radiation can produce the linear polarization under this special magnetic field topology. Turbulent Faraday rotation measure (RM) of this slab makes strong wavelength-dependent depolarization. The jitter photons can also scatter with those magnetic clumps inside the turbulent slab, and a nonzero variance of the Stokes parameter V can be generated. Furthermore, the linearly and circularly polarized photons in the optical and radio bands may suffer heavy absorptions from the slab. Thus we consider the polarized jitter radiation transfer processes. Finally, we compare our model results with the optical detections of GRB 091018, GRB 121024A, and GRB 131030A. We suggest simultaneous observations of GRB multi-wavelength polarization in the future.

Ultrashort x-ray pulse generation by nonlinear Thomson scattering of a relativistic electron with an intense circularly polarized laser pulse

Directory of Open Access Journals (Sweden)

F. Liu

2012-07-01

Full Text Available The nonlinear Thomson scattering of a relativistic electron with an intense laser pulse is calculated numerically. The results show that an ultrashort x-ray pulse can be generated by an electron with an initial energy of 5 MeV propagating across a circularly polarized laser pulse with a duration of 8 femtosecond and an intensity of about 1.1×10^{21}  W/cm^{2}, when the detection direction is perpendicular to the propagation directions of both the electron and the laser beam. The optimal values of the carrier-envelop phase and the intensity of the laser pulse for the generation of a single ultrashort x-ray pulse are obtained and verified by our calculations of the radiation characteristics.

A survey of synchrotron radiation devices producing circular or variable polarization

International Nuclear Information System (INIS)

Kim, K.J.

1990-01-01

This paper reviews the properties and operating principles of the new types of synchrotron radiation devices that produce circular polarization, or polarization that can be modulated in arbitrary fashion

High Performance Circularly Polarized Microstrip Antenna

Science.gov (United States)

Bondyopadhyay, Probir K. (Inventor)

1997-01-01

A microstrip antenna for radiating circularly polarized electromagnetic waves comprising a cluster array of at least four microstrip radiator elements, each of which is provided with dual orthogonal coplanar feeds in phase quadrature relation achieved by connection to an asymmetric T-junction power divider impedance notched at resonance. The dual fed circularly polarized reference element is positioned with its axis at a 45 deg angle with respect to the unit cell axis. The other three dual fed elements in the unit cell are positioned and fed with a coplanar feed structure with sequential rotation and phasing to enhance the axial ratio and impedance matching performance over a wide bandwidth. The centers of the radiator elements are disposed at the corners of a square with each side of a length d in the range of 0.7 to 0.9 times the free space wavelength of the antenna radiation and the radiator elements reside in a square unit cell area of sides equal to 2d and thereby permit the array to be used as a phased array antenna for electronic scanning and is realizable in a high temperature superconducting thin film material for high efficiency.

Bandwidth broadening of a graphene-based circular polarization converter by phase compensation.

Science.gov (United States)

Gao, Xi; Yang, Wanli; Cao, Weiping; Chen, Ming; Jiang, Yannan; Yu, Xinhua; Li, Haiou

2017-10-02

We present a broadband tunable circular polarization converter composed of a single graphene sheet patterned with butterfly-shaped holes, a dielectric spacer, and a 7-layer graphene ground plane. It can convert a linearly polarized wave into a circularly polarized wave in reflection mode. The polarization converter can be dynamically tuned by varying the Fermi energy of the single graphene sheet. Furthermore, the 7-layer graphene acting as a ground plane can modulate the phase of its reflected wave by controlling the Femi energy, which provides constructive interference condition at the surface of the single graphene sheet in a broad bandwidth and therefore significantly broadens the tunable bandwidth of the proposed polarization converter.

Imaging linear and circular polarization features in leaves with complete Mueller matrix polarimetry.

Science.gov (United States)

Patty, C H Lucas; Luo, David A; Snik, Frans; Ariese, Freek; Buma, Wybren Jan; Ten Kate, Inge Loes; van Spanning, Rob J M; Sparks, William B; Germer, Thomas A; Garab, Győző; Kudenov, Michael W

2018-06-01

Spectropolarimetry of intact plant leaves allows to probe the molecular architecture of vegetation photosynthesis in a non-invasive and non-destructive way and, as such, can offer a wealth of physiological information. In addition to the molecular signals due to the photosynthetic machinery, the cell structure and its arrangement within a leaf can create and modify polarization signals. Using Mueller matrix polarimetry with rotating retarder modulation, we have visualized spatial variations in polarization in transmission around the chlorophyll a absorbance band from 650 nm to 710 nm. We show linear and circular polarization measurements of maple leaves and cultivated maize leaves and discuss the corresponding Mueller matrices and the Mueller matrix decompositions, which show distinct features in diattenuation, polarizance, retardance and depolarization. Importantly, while normal leaf tissue shows a typical split signal with both a negative and a positive peak in the induced fractional circular polarization and circular dichroism, the signals close to the veins only display a negative band. The results are similar to the negative band as reported earlier for single macrodomains. We discuss the possible role of the chloroplast orientation around the veins as a cause of this phenomenon. Systematic artefacts are ruled out as three independent measurements by different instruments gave similar results. These results provide better insight into circular polarization measurements on whole leaves and options for vegetation remote sensing using circular polarization. Copyright © 2018 The Author(s). Published by Elsevier B.V. All rights reserved.

Dual Circularly Polarized Omnidirectional Antenna with Slot Array on Coaxial Cylinder

Directory of Open Access Journals (Sweden)

Bin Zhou

2015-01-01

Full Text Available A dual circularly polarized (CP omnidirectional antenna based on slot array in coaxial cylinder structure is presented in this paper. It is constructed by perpendicular slot pairs around and along the axis of the coaxial cylinder to realize the omnidirectional CP property, and two ports are assigned in its two sides as left hand circularly polarized (LHCP port and right hand circularly polarized (RHCP port, respectively. The proposed antenna achieves a bandwidth of 16.4% ranging from 5.05 to 5.95 GHz with an isolation higher than 15 dB between the two CP ports, and the return loss (RL is higher than 10 dB within the bandwidth in both of the two ports. From the measured results, the average axial ratio (AR of the proposed antenna in omnidirectional plane is lower than 1.5 dB.

Beamline 9.3.2 - a high-resolution, bend-magnet beamline with circular polarization capability

Energy Technology Data Exchange (ETDEWEB)

Moler, E.J.; Hussain, Z.; Howells, M.R. [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

Beamline 9.3.2 is a high resolution, SGM beamline on an ALS bending magnet with access to photon energies from 30-1500 eV. Features include circular polarization capability, a rotating chamber platform that allows switching between experiments without breaking vacuum, an active feedback system that keeps the beam centered on the entrance slit of the monochromator, and a bendable refocusing mirror. The beamline optics consist of horizontally and vertically focussing mirrors, a Spherical Grating Monochromator (SGM) with movable entrance and exit slits, and a bendable refocussing mirror. In addition, a movable aperature has been installed just upstream of the vertically focussing mirror which can select the x-rays above or below the plane of the synchrotron storage ring, allowing the user to select circularly or linearly polarized light. Circularly polarized x-rays are used to study the magnetic properties of materials. Beamline 9.3.2 can supply left and right circularly polarized x-rays by a computer controlled aperture which may be placed above or below the plane of the synchrotron storage ring. The degree of linear and circular polarization has been measured and calibrated.

Simulation of erasure of photoinduced anisotropy by circularly polarized light

DEFF Research Database (Denmark)

Sajti, Sz.; Kerekes, Á.; Barabás, M.

2001-01-01

The temporal evolution of photoinduced birefringence is investigated on the basis of a model proposed by Pedersen and co-workers, This model is extended for the case of elliptically polarized light, and used to describe the erasure of photoinduced birefringence by circularly polarized light...

Broadband Circularly Polarized Slot Antenna Loaded by a Multiple-Circular-Sector Patch.

Science.gov (United States)

Trinh-Van, Son; Yang, Youngoo; Lee, Kang-Yoon; Hwang, Keum Cheol

2018-05-15

In this paper, a microstrip-fed broadband circularly polarized (CP) slot antenna is presented. CP operation can be attained simply by embedding an S-shaped strip. By loading with a multiple-circular-sector patch, which consists of 12 circular-sector patches with identical central angles of 30° and different radii, the 3 dB axial ratio (AR) bandwidth is significantly broadened. To validate the performance of the proposed antenna, an antenna prototype is fabricated and tested. The fabricated antenna is 54 mm × 54 mm × 0.8 mm in size. The measured -10 dB reflection and 3 dB AR bandwidths are 81.06% (1.68⁻3.97 GHz) and 70.55% (1.89⁻3.95 GHz), respectively. Within the 3 dB AR bandwidth, the measured peak gain is 3.81 dBic. Reasonable agreement is also obtained between the measured and simulated results.

Polymer photovoltaic cells sensitive to the circular polarization ofl light

NARCIS (Netherlands)

Gilot, J.; Abbel, R.J.; Lakhwani, G.; Meijer, E.W.; Schenning, A.P.H.J.; Meskers, S.C.J.

2009-01-01

Chiral conjugated polymer is used to construct a photovoltaic cell whose response depends on the circular polarization of the incoming light. The selectivity for left and right polarized light as a function of the thickness of the polymer layer is accounted for by modeling of the optical properties

Photoconductive detector of circularly polarized radiation based on a MIS structure with a CoPt layer

Science.gov (United States)

Kudrin, A. V.; Dorokhin, M. V.; Zdoroveishchev, A. V.; Demina, P. B.; Vikhrova, O. V.; Kalent'eva, I. L.; Ved', M. V.

2017-11-01

A photoconductive detector of circularly polarized radiation based on the metal-insulator-semiconductor structure of CoPt/(Al2O3/SiO2/Al2O3)/InGaAs/GaAs is created. The efficiency of detection of circularly polarized radiation is 0.75% at room temperature. The operation of the detector is based on the manifestation of the effect of magnetic circular dichroism in the CoPt layer, that is, the dependence of the CoPt transmission coefficient on the sign of the circular polarization of light and magnetization.

Diffusion weighted imaging with circularly polarized oscillating gradients

DEFF Research Database (Denmark)

Lundell, Henrik; Sønderby, Casper Kaae; Dyrby, Tim B

2015-01-01

presented. One major hurdle in practical implementation is the low effective diffusion weighting provided at high frequency with limited gradient strength. THEORY: As a solution to the low diffusion weighting of OGSE, circularly polarized OGSE (CP-OGSE) is introduced. CP-OGSE gives a twofold increase...

In-line production of a bi-circular field for generation of helically polarized high-order harmonics

Energy Technology Data Exchange (ETDEWEB)

Kfir, Ofer, E-mail: ofertx@technion.ac.il, E-mail: oren@si.technion.ac.il; Bordo, Eliyahu; Ilan Haham, Gil; Lahav, Oren; Cohen, Oren, E-mail: ofertx@technion.ac.il, E-mail: oren@si.technion.ac.il [Solid State Institute and Physics Department, Technion, Haifa 32000 (Israel); Fleischer, Avner [Solid State Institute and Physics Department, Technion, Haifa 32000 (Israel); Department of Physics and Optical Engineering, Ort Braude College, Karmiel 21982 (Israel)

2016-05-23

The recent demonstration of bright circularly polarized high-order harmonics of a bi-circular pump field gave rise to new opportunities in ultrafast chiral science. In previous works, the required nontrivial bi-circular pump field was produced using a relatively complicated and sensitive Mach-Zehnder-like interferometer. We propose a compact and stable in-line apparatus for converting a quasi-monochromatic linearly polarized ultrashort driving laser field into a bi-circular field and employ it for generation of helically polarized high-harmonics. Furthermore, utilizing the apparatus for a spectroscopic spin-mixing measurement, we identify the photon spins of the bi-circular weak component field that are annihilated during the high harmonics process.

Realizing Broadband and Invertible Linear-to-circular Polarization Converter with Ultrathin Single-layer Metasurface

Science.gov (United States)

Li, Zhancheng; Liu, Wenwei; Cheng, Hua; Chen, Shuqi; Tian, Jianguo

2015-01-01

The arbitrary control of the polarization states of light has attracted the interest of the scientific community because of the wide range of modern optical applications that such control can afford. However, conventional polarization control setups are bulky and very often operate only within a narrow wavelength range, thereby resisting optical system miniaturization and integration. Here, we present the basic theory, simulated demonstration, and in-depth analysis of a high-performance broadband and invertible linear-to-circular (LTC) polarization converter composed of a single-layer gold nanorod array with a total thickness of ~λ/70 for the near-infrared regime. This setup can transform a circularly polarized wave into a linearly polarized one or a linearly polarized wave with a wavelength-dependent electric field polarization angle into a circularly polarized one in the transmission mode. The broadband and invertible LTC polarization conversion can be attributed to the tailoring of the light interference at the subwavelength scale via the induction of the anisotropic optical resonance mode. This ultrathin single-layer metasurface relaxes the high-precision requirements of the structure parameters in general metasurfaces while retaining the polarization conversion performance. Our findings open up intriguing possibilities towards the realization of novel integrated metasurface-based photonics devices for polarization manipulation, modulation, and phase retardation. PMID:26667360

Comparison study for multiple ionization of carbonyl sulfide by linearly and circularly polarized intense femtosecond laser fields using Coulomb explosion imaging

Science.gov (United States)

Ma, Pan; Wang, Chuncheng; Luo, Sizuo; Yu, Xitao; Li, Xiaokai; Wang, Zhenzhen; Hu, Wenhui; Yu, Jiaqi; Yang, Yizhang; Tian, Xu; Cui, Zhonghua; Ding, Dajun

2018-05-01

We studied the relative yields and dissociation dynamics for two- and three-body Coulomb explosion (CE) channels from highly charged carbonyl sulfide molecules in intense laser fields using the CE imaging technique. The electron recollision contributions are evaluated by comparing the relative yields for the multiple ionization process in linearly polarized and circularly polarized (LP and CP) laser fields. The nonsequential multiple ionization is only confirmed for the charge states of 2 to 4 because the energy for further ionization from the inner orbital is much larger than the maximum recollision energy, 3.2U p . The novel deviations of kinetic energy releases distributions between LP and CP pulses are observed for the charge states higher than 4. It can be attributed to the stronger molecular bending in highly charged states before three-body CE with CP light, in which the bending wave packet is initialed by the triple or quartic ionization and spread along their potential curves. Compared to LP light, CP light ionizes a larger fraction of bending molecules in the polarization plane.

Near-field circular polarization probed by chiral polyfluorene

NARCIS (Netherlands)

Savoini, M.; Biagioni, P.; Lakhwani, G.; Meskers, S.C.J.; Duò, L.; Finazzi, M.

2009-01-01

We demonstrate that a high degree of circular polarization can be delivered to the near field (NF) of an aperture at the apex of hollow-pyramid probes for scanning optical microscopy. This result is achieved by analyzing the dichroic properties of an annealed thin polymer film containing a chiral

A New Dual Circularly Polarized Feed Employing a Dielectric Cylinder-Loaded Circular Waveguide Open End Fed by Crossed Dipoles

Directory of Open Access Journals (Sweden)

Jae-Hoon Bang

2016-01-01

Full Text Available This paper presents a new dual circularly polarized feed that provides good axial ratio over wide angles and low cross-polarized radiation in backward direction. A circular waveguide open end is fed with two orthogonally polarized waves in phase quadrature by a pair of printed crossed dipoles and a compact connectorized quadrature hybrid coupler. The waveguide aperture is loaded with a dielectric cylinder to reduce the cross-polarization beyond 90 degrees off the boresight. The fabricated feed has, at 5.5 GHz, 6.33-dBic copolarized gain, 3-dB beamwidth of 106°, 10-dB beamwidth of 195°, 3-dB axial ratio beamwidth of 215°, maximum cross-polarized gain of −21.4 dBic, and 27-dB port isolation. The reflection coefficient of the feed is less than −10 dB at 4.99–6.09 GHz.

Electron spin polarization in realistic trajectories around the magnetic node of two counter-propagating, circularly polarized, ultra-intense lasers

Science.gov (United States)

Del Sorbo, D.; Seipt, D.; Thomas, A. G. R.; Ridgers, C. P.

2018-06-01

It has recently been suggested that two counter-propagating, circularly polarized, ultra-intense lasers can induce a strong electron spin polarization at the magnetic node of the electromagnetic field that they setup (Del Sorbo et al 2017 Phys. Rev. A 96 043407). We confirm these results by considering a more sophisticated description that integrates over realistic trajectories. The electron dynamics is weakly affected by the variation of power radiated due to the spin polarization. The degree of spin polarization differs by approximately 5% if considering electrons initially at rest or already in a circular orbit. The instability of trajectories at the magnetic node induces a spin precession associated with the electron migration that establishes an upper temporal limit to the polarization of the electron population of about one laser period.

Magnetic field effects on ultrafast lattice compression dynamics of Si(111) crystal when excited by linearly-polarized femtosecond laser pulses

Science.gov (United States)

Hatanaka, Koji; Odaka, Hideho; Ono, Kimitoshi; Fukumura, Hiroshi

2007-03-01

Time-resolved X-ray diffraction measurements of Si (111) single crystal are performed when excited by linearly-polarized femtosecond laser pulses (780 nm, 260 fs, negatively-chirped, 1 kHz) under a magnetic field (0.47 T). Laser fluence on the sample surface is 40 mJ/cm^2, which is enough lower than the ablation threshold at 200 mJ/cm^2. Probing X-ray pulses of iron characteristic X-ray lines at 0.193604 and 0.193998 nm are generated by focusing femtosecond laser pulses onto audio-cassette tapes in air. Linearly-polarized femtosecond laser pulse irradiation onto Si(111) crystal surface induces transient lattice compression in the picosecond time range, which is confirmed by transient angle shift of X-ray diffraction to higher angles. Little difference of compression dynamics is observed when the laser polarization is changed from p to s-pol. without a magnetic field. On the other hand, under a magnetic field, the lattice compression dynamics changes when the laser is p-polarized which is vertical to the magnetic field vector. These results may be assigned to photo-carrier formation and energy-band distortion.

Astronomy in Denver: Probing Interstellar Circular Polarization with Polvis, a Full Stokes Single Shot Polarimeter

Science.gov (United States)

Wolfe, Tristan; Stencel, Robert E.

2018-06-01

Measurements of optical circular polarization (Stokes V) introduced by dust grains in the ISM are important for two main reasons. First of all, the polarization itself contains information about the metallic versus dielectric composition of the dust grains themselves (H. C. van de Hulst 1957, textbook). Additionally, circular polarization can help constrain the interstellar component of the polarization of any source that may have intrinsic polarization, which needs to be calibrated for astrophysical study. Though interstellar circular polarization has been observed (P. G. Martin 1972, MNRAS 159), most broadband measurements of ISM polarization include linear polarization only (Stokes Q and U), due to the relatively low circular polarization signal and the added instrumentation complexity of including V-measurement capability. Prior circular polarization measurements have also received very little follow-up in the past several decades, even as polarimeters have become more accurate due to advances in technology. The University of Denver is pursuing these studies with POLVIS, a prototype polarimeter that utilizes a stress-engineered optic ("SEO", A. K. Spilman and T. G. Brown 2007, Applied Optics IP 46) to produce polarization-dependent PSFs (A. M. Beckley and T. G. Brown 2010, Proc SPIE 7570). These PSFs are analyzed to provide simultaneous Stokes I, Q, U, and V measurements, in a single beam and single image, along the line-of-sight to point source-like objects. Polvis is the first polarimeter to apply these optics and measurement techniques for astronomical observations. We present the first results of this instrument in B, V, and R wavebands, providing a fresh look at full Stokes interstellar polarization. Importantly, this set of efforts will constrain the ISM contribution to the polarization with respect to intrinsic stellar components. The authors are grateful to the estate of William Herschel Womble for the support of astronomy at the University of Denver

Inkjet printed circularly polarized antennas for GPS applications

KAUST Repository

Farooqui, Muhammad Fahad; Shamim, Atif

2014-01-01

gain of 0.2 dBi at 1.575 GHz with 3-dB axial ratio bandwidth of 3.8%. The second antenna design comprises a modified monopole in the form of an inverted L and has been termed as circularly polarized inverted L antenna (CILA). The antenna shows a gain

Photoemission of Bi_{2}Se_{3} with Circularly Polarized Light: Probe of Spin Polarization or Means for Spin Manipulation?

Directory of Open Access Journals (Sweden)

J. Sánchez-Barriga

2014-03-01

Full Text Available Topological insulators are characterized by Dirac-cone surface states with electron spins locked perpendicular to their linear momenta. Recent theoretical and experimental work implied that this specific spin texture should enable control of photoelectron spins by circularly polarized light. However, these reports questioned the so far accepted interpretation of spin-resolved photoelectron spectroscopy. We solve this puzzle and show that vacuum ultraviolet photons (50–70 eV with linear or circular polarization indeed probe the initial-state spin texture of Bi_{2}Se_{3} while circularly polarized 6-eV low-energy photons flip the electron spins out of plane and reverse their spin polarization, with its sign determined by the light helicity. Our photoemission calculations, taking into account the interplay between the varying probing depth, dipole-selection rules, and spin-dependent scattering effects involving initial and final states, explain these findings and reveal proper conditions for light-induced spin manipulation. Our results pave the way for future applications of topological insulators in optospintronic devices.

Electrical access to critical coupling of circularly polarized waves in graphene chiral metamaterials.

Science.gov (United States)

Kim, Teun-Teun; Oh, Sang Soon; Kim, Hyeon-Don; Park, Hyun Sung; Hess, Ortwin; Min, Bumki; Zhang, Shuang

2017-09-01

Active control of polarization states of electromagnetic waves is highly desirable because of its diverse applications in information processing, telecommunications, and spectroscopy. However, despite the recent advances using artificial materials, most active polarization control schemes require optical stimuli necessitating complex optical setups. We experimentally demonstrate an alternative-direct electrical tuning of the polarization state of terahertz waves. Combining a chiral metamaterial with a gated single-layer sheet of graphene, we show that transmission of a terahertz wave with one circular polarization can be electrically controlled without affecting that of the other circular polarization, leading to large-intensity modulation depths (>99%) with a low gate voltage. This effective control of polarization is made possible by the full accessibility of three coupling regimes, that is, underdamped, critically damped, and overdamped regimes by electrical control of the graphene properties.

Construction and performance of BL28 of the Photon Factory for circularly polarized synchrotron radiation

International Nuclear Information System (INIS)

Kagoshima, Y.; Muto, S.; Miyahara, T.; Koide, T.; Yamamoto, S.; Kitamura, H.

1992-01-01

A branch beamline, BL28A, has been constructed for the application of circularly polarized vacuum ultraviolet radiation. The radiation can be obtained in the helical undulator operation mode of an insertion device, EMPW number-sign 28, which is also cut for elliptically polarized hard x-ray radiation. T first harmonic of the helical undulator radiation can be tuned from 40 to 350 eV with its corresponding K value from 3 to 0.2. A monochromator working basically with constant deviation optics was installed, and has started its operation. A circularly polarized flux of ∼10 10 photons/s has been achieved with energy resolution of around 500--1000 at the first harmonic peak. The circular polarization after the monochromator was estimated to be higher than 70% by comparing theory and experiment on the magnetic circular dichroism of nickel films in the 3p-3d excitation region. The design philosophy of the beamline and recent results on the performance tests are presented

Construction and performance of BL28 of the Photon Factory for circularly polarized synchrotron radiation

Science.gov (United States)

Kagoshima, Yasushi; Muto, Sadatsugu; Miyahara, Tsuneaki; Koide, Tsuneharu; Yamamoto, Shigeru; Kitamura, Hideo

1992-01-01

A branch beamline, BL28A, has been constructed for the application of circularly polarized vacuum ultraviolet radiation. The radiation can be obtained in the helical undulator operation mode of an insertion device, EMPW♯28, which is also cut for elliptically polarized hard x-ray radiation. T first harmonic of the helical undulator radiation can be tuned from 40 to 350 eV with its corresponding K value from 3 to 0.2. A monochromator working basically with constant deviation optics was installed, and has started its operation. A circularly polarized flux of ˜1010 photons/s has been achieved with energy resolution of around 500-1000 at the first harmonic peak. The circular polarization after the monochromator was estimated to be higher than 70% by comparing theory and experiment on the magnetic circular dichroism of nickel films in the 3p-3d excitation region. The design philosophy of the beamline and recent results on the performance tests are presented.

Polarization dependent switching of asymmetric nanorings with a circular field

Directory of Open Access Journals (Sweden)

Nihar R. Pradhan

2016-01-01

Full Text Available We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

Circular polarization of light by planet Mercury and enantiomorphism of its surface minerals.

Science.gov (United States)

Meierhenrich, Uwe J; Thiemann, Wolfram H P; Barbier, Bernard; Brack, André; Alcaraz, Christian; Nahon, Laurent; Wolstencroft, Ray

2002-04-01

Different mechanisms for the generation of circular polarization by the surface of planets and satellites are described. The observed values for Venus, the Moon, Mars, and Jupiter obtained by photo-polarimetric measurements with Earth based telescopes, showed accordance with theory. However, for planet Mercury asymmetric parameters in the circular polarization were measured that do not fit with calculations. For BepiColombo, the ESA cornerstone mission 5 to Mercury, we propose to investigate this phenomenon using a concept which includes two instruments. The first instrument is a high-resolution optical polarimeter, capable to determine and map the circular polarization by remote scanning of Mercury's surface from the Mercury Planetary Orbiter MPO. The second instrument is an in situ sensor for the detection of the enantiomorphism of surface crystals and minerals, proposed to be included in the Mercury Lander MSE.

Ionization of oriented carbonyl sulfide molecules by intense circularly polarized laser pulses

DEFF Research Database (Denmark)

Dimitrovski, Darko; Abu-Samha, Mahmoud; Madsen, Lars Bojer

2011-01-01

We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molec......We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction......-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron...

Circular polarization opportunities at the SASE3 undulator line of the European XFEL

Energy Technology Data Exchange (ETDEWEB)

Serkez, Svitozar; Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2016-08-15

XFELs provide X-ray pulses with unprecedented peak brightness and ultrashort duration. They are usually driven by planar undulators, meaning that the output radiation is linearly polarized. For many experimental applications, however, polarization control is critical: besides the ability to produce linearly polarized radiation, one often needs the possibility of generating circularly polarized radiation with a high, stable degree of polarization. This may be achieved by using a first part of the XFEL undulator to produce bunching and then, by propagating the the bunched beam through an ''afterburner'' - a short undulator with tunable polarization, where only limited gain takes place. One of the issues that one needs to consider in this case is the separation of the circularly polarized radiation obtained in the radiator from the linearly polarized background produced in the first part of the FEL. In this article we review several methods to do so, including the inverse tapering technique. In particular, we use the Genesis FEL code to simulate a case study pertaining to the SASE3 FEL line at the European XFEL with up-to-date parameters and we confirm that a high degree of circular polarization is expected. Moreover, we propose to further improve the effectiveness of the inverse tapering technique either via angular separation of the linearly polarized radiation or strongly defocusing it at the sample position. In this way we exploit the unique flexibility of the European XFEL from both the electron beam and the photon beam optics side.

High-flux normal incidence monochromator for circularly polarized synchrotron radiation

International Nuclear Information System (INIS)

Schaefers, F.; Peatman, W.; Eyers, A.; Heckenkamp, C.; Schoenhense, G.; Heinzmann, U.

1986-01-01

A 6.5-m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low-signal experiments such as spin- and angle-resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk--Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 10 11 photons s -1 bandwidth -1 (0.2--0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved

Negative circular polarization emissions from WSe2/MoSe2 commensurate heterobilayers

KAUST Repository

Hsu, Wei-Ting; Lu, Li-Syuan; Wu, Po-Hsun; Lee, Ming-Hao; Chen, Peng-Jen; Wu, Pei-Ying; Chou, Yi-Chia; Jeng, Horng-Tay; Li, Lain-Jong; Chu, Ming-Wen; Chang, Wen-Hao

2018-01-01

Van der Waals heterobilayers of transition metal dichalcogenides with spin-valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe/MoSe heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities.

Negative circular polarization emissions from WSe2/MoSe2 commensurate heterobilayers

KAUST Repository

Hsu, Wei-Ting

2018-04-11

Van der Waals heterobilayers of transition metal dichalcogenides with spin-valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe/MoSe heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities.

Measurement of the circular polarization in radio emission from extensive air showers confirms emission mechanisms

NARCIS (Netherlands)

Scholten, O.; Trinh, T. N. G.; Bonardi, A.; Buitink, S.; Correa, P.; Corstanje, A.; Hasankiadeh, Q. Dorosti; Falcke, H.; Horandel, J. R.; Mitra, P.; Mulrey, K.; Nelles, A.; Rachen, J. P.; Rossetto, L.; Schellart, P.; Thoudam, S.; ter Veen, S.; de Vries, K. D.; Winchen, T.

2016-01-01

We report here on a novel analysis of the complete set of four Stokes parameters that uniquely determine the linear and/or circular polarization of the radio signal for an extensive air shower. The observed dependency of the circular polarization on azimuth angle and distance to the shower axis is a

A Novel Dual-Band Circularly Polarized Rectangular Slot Antenna

Directory of Open Access Journals (Sweden)

Biao Li

2016-01-01

Full Text Available A coplanar waveguide fed dual-band circularly polarized rectangular slot antenna is presented. The proposed antenna consists of a rectangular metal frame acting as a ground and an S-shaped monopole as a radiator. The spatial distribution of the surface current density is employed to demonstrate that the circular polarization is generated by the S-shaped monopole which controls the path of the surface currents. An antenna prototype, having overall dimension 37 × 37 × 1 mm3, has been fabricated on FR4 substrate with dielectric constant 4.4. The proposed antenna achieves 10 dB return loss bandwidths and 3 dB axial ratio (AR in the frequency bands 2.39–2.81 GHz and 5.42–5.92 GHz, respectively. Both these characteristics are suitable for WLAN and WiMAX applications.

Colloidal InP/ZnS core-shell nanocrystals studied by linearly and circularly polarized photoluminescence

International Nuclear Information System (INIS)

Langof, L.; Fradkin, L.; Ehrenfreund, E.; Lifshitz, E.; Micic, O.I.; Nozik, A.J.

2004-01-01

The magneto-optical properties of InP/ZnS core-shell nanocrystals (NCs) were investigated by measuring the degree of linear and circular polarization of photoluminescence (PL) spectra, in the presence of an external magnetic field under resonant or non-resonant excitation. The linearly polarized PL data strongly indicate that InP/ZnS NCs have a prolongated shape. The resonant-excited circularly polarized PL decay curves indicate that the spin relaxation time of the studied samples is shorter than the radiative lifetime of their exciton. Furthermore, the magnetic field-induced circularly polarized PL process reveals an exciton g factor (g ex ) of 0.55. Thus, such studies may serve as a tool to directly estimate the NC's shape anisotropy and to determine the g-factor of charge carriers and excitons in those NCs

Colloidal InP/ZnS core shell nanocrystals studied by linearly and circularly polarized photoluminescence

Science.gov (United States)

Langof, L.; Fradkin, L.; Ehrenfreund, E.; Lifshitz, E.; Micic, O. I.; Nozik, A. J.

2004-02-01

The magneto-optical properties of InP/ZnS core-shell nanocrystals (NCs) were investigated by measuring the degree of linear and circular polarization of photoluminescence (PL) spectra, in the presence of an external magnetic field under resonant or non-resonant excitation. The linearly polarized PL data strongly indicate that InP/ZnS NCs have a prolongated shape. The resonant-excited circularly polarized PL decay curves indicate that the spin relaxation time of the studied samples is shorter than the radiative lifetime of their exciton. Furthermore, the magnetic field-induced circularly polarized PL process reveals an exciton g factor ( gex) of 0.55. Thus, such studies may serve as a tool to directly estimate the NC's shape anisotropy and to determine the g-factor of charge carriers and excitons in those NCs.

Circular-Polarization-Selective Transmission Induced by Spin-Orbit Coupling in a Helical Tape Waveguide

Science.gov (United States)

Liu, Yahong; Guo, Qinghua; Liu, Hongchao; Liu, Congcong; Song, Kun; Yang, Biao; Hou, Quanwen; Zhao, Xiaopeng; Zhang, Shuang; Navarro-Cía, Miguel

2018-05-01

Spin-orbit coupling of light, describing the interaction between the polarization (spin) and spatial degrees of freedom (orbit) of light, plays an important role in subwavelength scale systems and leads to many interesting phenomena, such as the spin Hall effect of light. Here, based on the spin-orbit coupling, we design and fabricate a helical tape waveguide (HTW), which can realize a circular-polarization-selective process. When the incident circularly polarized wave is of the same handedness as the helix of the HTW, a nearly complete transmission is observed; in contrast, a counterrotating circular polarization of incident wave results in a much lower transmission or is even totally blocked by the HTW. Indeed, both simulations and experiments reveal that the blocked component of power leaks through the helical aperture of the HTW and forms a conical beam analogous to helical Cherenkov radiation due to the conversion from the spin angular momentum to the orbital angular momentum. Our HTW structure demonstrates its potential as a polarization selector in a broadband frequency range.

Ultra-wideband circular-polarization converter with micro-split Jerusalem-cross metasurfaces

Science.gov (United States)

Gao, Xi; Yu, Xing-Yang; Cao, Wei-Ping; Jiang, Yan-Nan; Yu, Xin-Hua

2016-12-01

An ultrathin micro-split Jerusalem-cross metasurface is proposed in this paper, which can efficiently convert the linear polarization of electromagnetic (EM) wave into the circular polarization in ultra-wideband. By symmetrically employing two micro-splits on the horizontal arm (in the x direction) of the Jerusalem-cross structure, the bandwidth of the proposed device is significantly extended. Both simulated and experimental results show that the proposed metasurface is able to convert linearly polarized waves into circularly polarized waves in a frequency range from 12.4 GHz to 21 GHz, with an axis ratio better than 1 dB. The simulated results also show that such a broadband and high-performance are maintained over a wide range of incident angle. The presented polarization converter can be used in a number of areas, such as spectroscopy and wireless communications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61461016 and 61661012), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant Nos. 2014GXNSFAA118366, 2014GXNSFAA118283, and 2015jjBB7002), and the Innovation Project of Graduate Education of Guilin University of Electronic Technology, China (Grant No. 2016YJCX82).

X-BAND CIRCULARLY POLARIZED RECTENNAS FOR MICROWAVE POWER TRANSMISSION APPLICATIONS

Institute of Scientific and Technical Information of China (English)

Yang Xuexia; Xu Junshu; Xu Deming; Xu Changlong

2008-01-01

Circularly polarized rectennas operating at X-band are studied in this paper. The quasi-square patches fed by aperture coupling are used as the circularly polarized receiving antennas,which are easily matched and integrated with the circuits of rectennas. The double-layer structure not only minimizes the size of the rectennas but also decreases the effects of the circuits on the antenna. The receiving elements have broader bandwidth and higher gain than the single-layer patches.Two rectennas operating at 10GHz are designed, fabricated and measured. The voltage of 3.86V on a load of 200Ωis measured and a high RF-DC conversion efficiency of 75% is obtained at 9.98GHz. It is convenient for this kind of rectennas to form large arrays for high power applications.

Colloidal InP/ZnS core-shell nanocrystals studied by linearly and circularly polarized photoluminescence

Energy Technology Data Exchange (ETDEWEB)

Langof, L.; Fradkin, L.; Ehrenfreund, E.; Lifshitz, E.; Micic, O.I.; Nozik, A.J

2004-02-16

The magneto-optical properties of InP/ZnS core-shell nanocrystals (NCs) were investigated by measuring the degree of linear and circular polarization of photoluminescence (PL) spectra, in the presence of an external magnetic field under resonant or non-resonant excitation. The linearly polarized PL data strongly indicate that InP/ZnS NCs have a prolongated shape. The resonant-excited circularly polarized PL decay curves indicate that the spin relaxation time of the studied samples is shorter than the radiative lifetime of their exciton. Furthermore, the magnetic field-induced circularly polarized PL process reveals an exciton g factor (g{sub ex}) of 0.55. Thus, such studies may serve as a tool to directly estimate the NC's shape anisotropy and to determine the g-factor of charge carriers and excitons in those NCs.

Circularly Polarized Luminescence from a Pyrene-Cyclodextrin Supra-Dendron.

Science.gov (United States)

Zhang, Yuening; Yang, Dong; Han, Jianlei; Zhou, Jin; Jin, Qingxian; Liu, Minghua; Duan, Pengfei

2018-05-22

Soft nanomaterials with circularly polarized luminescence (CPL) have been currently attracting great interest. Here, we report a pyrene-containing π-peptide dendron hydrogel, which shows 1D and 2D nanostructures with varied CPL activities. It was found that the individual dendrons formed hydrogels in a wide pH range (3-12) and self-assembled into helices with pH-tuned pitches. Through chirality transfer, the pyrene unit could show CPL originated from both the monomer and excimer bands. When cyclodextrin was introduced, different supra-dendrons were obtained with β-cyclodextrin (PGAc@β-CD) and γ-cyclodextrin (PGAc@γ-CD) through host-guest interactions, respectively. Interestingly, the PGAc@β-CD and PGAc@γ-CD supra-dendrons self-assembled into 2D nanosheet and entangled nanofibers, respectively, showing cyclodextrin induced circularly polarized emission from both the monomer and excimer bands of the pyrene moiety. Thus, through a simple host-guest interaction, both the nanostructures and the chiroptical activities could be modulated.

Miniature magnetic bottle confined by circularly polarized laser light and measurements of the inverse Faraday effect in plasmas

International Nuclear Information System (INIS)

Eliezer, S.; Paiss, Y.; Horovitz, Y.; Henis, Z.

1997-01-01

A new concept of hot plasma confinement in a miniature magnetic bottle induced by circularly polarized laser light is suggested. Magnetic fields generated by circularly polarized laser light may be of the order of megagauss, depending on the laser intensity. In this configuration the circularly polarized light is used to obtain confinement of a plasma contained in a good conductor vessel. The confinement in this scheme is supported by the magnetic forces. The Lawson criterion for a DT plasma might be achieved for number density n = 5*10 21 cm -3 and confinement time τ= 20 ns. The laser and plasma parameters required to obtain an energetic gain are calculated. Experiments and preliminary calculations were performed to study the feasibility of the above scheme. Measurements of the axial magnetic field induced by circularly polarized laser light, the so called inverse Faraday effect, and of the absorption of circularly polarized laser light in plasma, are reported. The experiments were performed with a circularly polarized Nd:YAG laser, having a wavelength of 1.06 τm and a pulse duration of 7 ns, in a range of irradiances from 10 9 to 10 14 W/cm 2 . Axial magnetic fields from 500 Gauss to 2 megagauss were measured. Up to 5*10 13 W/cm 3 the results are in agreement with a nonlinear model of the inverse Faraday effect dominated by the ponderomotive force. For the laser irradiance studied here, 9*10 13 - 2.5*10 14 W/cm 2 , the absorption of circularly polarized light was 14% higher relative to the absorption of linear polarized light

Variation of linear and circular polarization persistence for changing field of view and collection area in a forward scattering environment

Science.gov (United States)

van der Laan, John D.; Wright, Jeremy B.; Scrymgeour, David A.; Kemme, Shanalyn A.; Dereniak, Eustace L.

2016-05-01

We present experimental and simulation results for a laboratory-based forward-scattering environment, where 1 μm diameter polystyrene spheres are suspended in water to model the optical scattering properties of fog. Circular polarization maintains its degree of polarization better than linear polarization as the optical thickness of the scattering environment increases. Both simulation and experiment quantify circular polarization's superior persistence, compared to that of linear polarization, and show that it is much less affected by variations in the field of view and collection area of the optical system. Our experimental environment's lateral extent was physically finite, causing a significant difference between measured and simulated degree of polarization values for incident linearly polarized light, but not for circularly polarized light. Through simulation we demonstrate that circular polarization is less susceptible to the finite environmental extent as well as the collection optic's limiting configuration.

Rydberg atoms in circular polarization: Classical stabilization in optical frequency fields

International Nuclear Information System (INIS)

Chism, Will; Reichl, L.E.

2002-01-01

We investigate the classical dynamics of the Rydberg atom in circularly polarized laser fields, restricted to the two-dimensional plane of polarization. We use a Poincare surface of section to study nonlinear resonance structures for optical frequency driving fields. We demonstrate the existence and morphology of these structures as the laser intensity transitions from moderate to intense

Control of emitted light polarization in a 1310 nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection

Energy Technology Data Exchange (ETDEWEB)

Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Hurtado, A.; Al Seyab, R. K.; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Korpijarvi, V.-M.; Guina, M. [Optoelectronics Research Centre (ORC), Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere (Finland)

2014-11-03

We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.

Circular polarization of gravitational waves from non-rotating supernova cores: a new probe into the pre-explosion hydrodynamics

Science.gov (United States)

Hayama, Kazuhiro; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

2018-06-01

We present an analysis of the circular polarization of gravitational waves (GWs) using results from three-dimensional (3D), general relativistic (GR) core-collapse simulations of a non-rotating 15 M⊙ star. For the signal detection, we perform a coherent network analysis taking into account the four interferometers of LIGO Hanford, LIGO Livingston, VIRGO, and KAGRA. We focus on the Stokes V parameter, which directly characterizes the asymmetry of the GW circular polarization. We find that the amplitude of the GW polarization becomes bigger for our 3D-GR model that exhibits strong activity of the standing accretion shock instability (SASI). Our results suggest that the SASI-induced accretion flows to the proto-neutron star (PNS) lead to a characteristic, low-frequency modulation (100-200 Hz) in both the waveform and the GW circular polarization. By estimating the signal-to-noise ratio of the GW polarization, we demonstrate that the detection horizon of the circular polarization extends by more than a factor of several times farther comparing to that of the GW amplitude. Our results suggest that the GW circular polarization, if detected, could provide a new probe into the pre-explosion hydrodynamics such as the SASI activity and the g-mode oscillation of the PNS.

Circular polarization of gravitational waves from non-rotating supernova cores: a new probe into the pre-explosion hydrodynamics

Science.gov (United States)

Hayama, Kazuhiro; Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya

2018-04-01

We present an analysis of the circular polarization of gravitational-waves (GWs) using results from three-dimensional (3D), general relativistic (GR) core-collapse simulations of a non-rotating 15M⊙ star. For the signal detection, we perform a coherent network analysis taking into account the four interferometers of LIGO Hanford, LIGO Livingston, VIRGO, and KAGRA. We focus on the Stokes V parameter, which directly characterizes the asymmetry of the GW circular polarization. We find that the amplitude of the GW polarization becomes bigger for our 3D-GR model that exhibits strong activity of the standing accretion shock instability (SASI). Our results suggest that the SASI-induced accretion flows to the proto-neutron star (PNS) lead to a characteristic, low-frequency modulation (100 ˜ 200 Hz) in both the waveform and the GW circular polarization. By estimating the signal-to-noise ratio of the GW polarization, we demonstrate that the detection horizon of the circular polarization extends by more than a factor of several times farther comparing to that of the GW amplitude. Our results suggest that the GW circular polarization, if detected, could provide a new probe into the pre-explosion hydrodynamics such as the SASI activity and the g-mode oscillation of the PNS.

Improvement of the crossed undulator design for effective circular polarization control in X-ray FELs

Energy Technology Data Exchange (ETDEWEB)

Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2011-01-15

The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90 %) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. The obvious and technically possible extension considered in this paper, is to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity switching, a high degree of circular polarization (over 95%) and a high output power level, comparable with the saturation power level in the baseline undulator at fundamental wavelength. We present feasibility study and exemplifications for the LCLS baseline in the soft X-ray regime. (orig.)

Chirality and energy transfer amplified circularly polarized luminescence in composite nanohelix

Science.gov (United States)

Yang, Dong; Duan, Pengfei; Zhang, Li; Liu, Minghua

2017-01-01

Transfer of both chirality and energy information plays an important role in biological systems. Here we show a chiral donor π-gelator and assembled it with an achiral π-acceptor to see how chirality and energy can be transferred in a composite donor–acceptor system. It is found that the individual chiral gelator can self-assemble into nanohelix. In the presence of the achiral acceptor, the self-assembly can also proceed and lead to the formation of the composite nanohelix. In the composite nanohelix, an energy transfer is realized. Interestingly, in the composite nanohelix, the achiral acceptor can both capture the supramolecular chirality and collect the circularly polarized energy from the chiral donor, showing both supramolecular chirality and energy transfer amplified circularly polarized luminescence (ETACPL). PMID:28585538

Circularly polarized antennas for active holographic imaging through barriers

Science.gov (United States)

McMakin, Douglas L [Richland, WA; Severtsen, Ronald H [Richland, WA; Lechelt, Wayne M [West Richland, WA; Prince, James M [Kennewick, WA

2011-07-26

Circularly-polarized antennas and their methods of use for active holographic imaging through barriers. The antennas are dielectrically loaded to optimally match the dielectric constant of the barrier through which images are to be produced. The dielectric loading helps to remove barrier-front surface reflections and to couple electromagnetic energy into the barrier.

Comparison of two superconducting elliptical undulators for generating circularly polarized light

Directory of Open Access Journals (Sweden)

C. S. Hwang

2004-09-01

Full Text Available The potential use of two planar superconducting elliptical undulators—a vertically wound racetrack coil structure and a staggered array structure—to generate a circularly polarized hard x-ray source was investigated. The magnetic poles and wires of the up and down magnet arrays were rotated in alternating directions on the horizontal plane, an elliptical field is generated to provide circularly polarized light in the electron-storage ring and the energy-recovery linac accelerator. Rapid switching between right- and left-circularly polarized radiations is performed using two undulators with oppositely rotated wires and poles. Given a periodic length of 15 mm and a gap of 5 mm, the magnetic-flux densities in the elliptical undulator are B_{z}=1.2   T (B_{x}=0.6   T and B_{z}=0.35   T (B_{x}=0.15   T in the planar vertically wound racetrack coil and the staggered structure with poles rotated by 35° and 25°, respectively. In maximizing the merit of the flux and the width of the effective field region in the two superconducting elliptical undulators, the trade-off rotation angles of the coils and poles are 20° and 5°, for vertically wound racetrack coil and staggered undulators, respectively.

A Minkowski Fractal Circularly Polarized Antenna for RFID Reader

Directory of Open Access Journals (Sweden)

Yanzhong Yu

2014-11-01

Full Text Available A design of fractal-like antenna with circular polarization for radio frequency identification (RFID reader applications is presented in this article. The modified Minkowski fractal structure is adopted as radiating patch for size reduction and broadband operation. A corner-truncated technology and a slot-opened method are employed to realize circular polarization and improve the gain of the proposed antenna, respectively. The proposed antenna is analyzed and optimized by HFSS. Return loss and maximum gain of the optimized antenna achieve to -22.2 dB and 1.12 dB at 920 MHz, respectively. The optimized design has an axial ratio (AR of 1.2 dB at central frequency of 920 MHz and impedance bandwidth (S11<=-10 dB of 40 MHz (4.3 %. Its input impedance is (57.9-j2.6 W that is close to input impedance of coaxial line (50 W. Numerical results demonstrate that the optimized antenna exhibits acceptable performances and may satisfy requirements of RFID reader applications.

Femtosecond laser-induced herringbone patterns

Science.gov (United States)

Garcell, Erik M.; Lam, Billy; Guo, Chunlei

2018-06-01

Femtosecond laser-induced herringbone patterns are formed on copper (Cu). These novel periodic structures are created following s-polarized, large incident angle, femtosecond laser pulses. Forming as slanted and axially symmetric laser-induced periodic surface structures along the side walls of ablated channels, the result is a series of v-shaped structures that resemble a herringbone pattern. Fluence mapping, incident angle studies, as well as polarization studies have been conducted and provide a clear understanding of this new structure.

Triband Omnidirectional Circularly Polarized Dielectric Resonator Antenna with Top-Loaded Alford Loop

Directory of Open Access Journals (Sweden)

Chunxia Cheng

2014-01-01

Full Text Available A triband omnidirectional circularly polarized dielectric resonator antenna with a top-loaded modified Alford loop for GSM, WLAN, and WiMAX applications is proposed. Fed by an axial probe, the DRA (dielectric resonator antenna radiates like a vertically polarized electric monopole. The top-loaded modified Alford loop provides an equivalent horizontally polarized magnetic dipole mode at triband. Omnidirectional CP (circular polarized fields can be obtained when the two orthogonally polarized fields are equal in amplitude with phase quadrature. The antenna has been successfully simulated, fabricated, and measured. The experimental and numerical results exhibit that the antenna can obtain usable CP bandwidths of 1.925–1.955 GHz, 2.36–2.48 GHz, and 3.502–3.53 GHz with return loss larger than 10 dB and axial ratio less than 3 dB. In addition, over the three bands, the antenna obtains very good omnidirectional CP radiation patterns in the azimuth plane. Moreover, an average CP gain in the azimuth plane of 1.2, 1.6, and −1.5 dBic for the lower, middle, and upper bands has been obtained.

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

CERN Document Server

Shvets, G

2002-01-01

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

International Nuclear Information System (INIS)

G. Shvets; N.J. Fisch; J.-M. Rax

2002-01-01

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation

Linear versus circular polarization of head coils - comparison on phantom and in the clinic

International Nuclear Information System (INIS)

Schratter, M.; Kramer, J.; Prayer, L.; Wimberger, D.; Imhof, H.; Schmid, W.

1990-01-01

Two different head coils - one with linear polarization and the other with circular polarization - were compared under the same measurement conditions. Comparison was done on a phantom with waterfilled and gadolinium-filled pin-holes, as well as on anatomical MR images of 23 volunteers. In three volunteers the whole brain was examined while, in the remaining 20 volunteers the sella region or cerebellopontine angleregion was examined. Criteria for comparison were signal-to-noise ratio, background noise, and detail resolution (phantom), as well as subjective criteria - image sharpness, anatomical, contrast, and recognition of anatomical details -, evaluated on anatomical MR images by four radiologists independently of each other. The results show a significant improvement of signal-to-noise ratio, lower background noise and therefore marked improvement of images harpness, and moderate improvement in the recognition of anatomical details using the circular polarized head coil; as for as detail resolution and anatomical contrast were concerned, however, no significant difference was seen between the two coils. Major advantages of the circular, polarized head coil in clinical application are shorter measurement times (reduced number of acquisitions), as well as thinner slices without loss of signal-to-noise ratio. (orig.) [de

Wideband Circularly Polarized Printed Ring Slot Antenna for 5 GHz – 6 GHz

Science.gov (United States)

Nasrun Osman, Mohamed; Rahim, Mohamad Helmi A.; Jusoh, Muzammil; Sabapathy, Thennarasan; Rahim, Mohamad Kamal A.; Norlyana Azemi, Saidatul

2018-03-01

This paper presents the design of circularly polarized printed slot antenna operating at 5 – 6 GHz. The proposed antenna consists of L-shaped feedline on the top of structure and circular ring slot positioned at the ground plane underneath the substrate as a radiator. A radial and narrow slot in the ground plane provides coupling between the L-shaped feedline and circular ring slot. The circular polarization is realized by implementing the slits perturbation located diagonally to perturb the current flow on the slot structure. The antenna prototype is fabricated on FR4 substrate. The simulated and measured results are compared and analyzed to demonstrate the performance of the antenna. Good measured of simulated results are obtained at the targeted operating frequency. The simulated -10dB reflection coefficient bandwidths and axial ratio are 750 MHz and 165 MHz, respectively. The investigation on the affect of the important parameters towards the reflection coefficient and axial are also presented. The proposed antenna is highly potential to be used for wireless local area network (WLAN) and wireless power transfer (WPT).

Circularly polarized light to study linear magneto-optics for ferrofluids: θ-scan technique

Science.gov (United States)

Meng, Xiangshen; Huang, Yan; He, Zhenghong; Lin, Yueqiang; Liu, Xiaodong; Li, Decai; Li, Jian; Qiu, Xiaoyan

2018-06-01

Circularly polarized light can be divided into two vertically linearly polarized light beams with  ±π/2 phase differences. In the presence of an external magnetic field, when circularly polarized light travels through a ferrofluid film, whose thickness is no more than that of λ/4 plate, magneto-optical, magnetic birefringence and dichroism effects cause the transmitted light to behave as elliptically polarized light. Using angular scan by a continuously rotating polarizer as analyzer, the angular (θ) distribution curve of relative intensity (T) corresponding to elliptically polarized light can be measured. From the T  ‑  θ curve having ellipsometry, the parameters such as the ratio of short to long axis, and angular orientation of the long axis to the vertical field direction can be obtained. Thus, magnetic birefringence and dichroism can be probed simultaneously by measuring magneto-optical, positive or negative birefringence and dichroism features from the transmission mode. The proposed method is called θ-scan technique, and can accurately determine sample stability, magnetic field direction, and cancel intrinsic light source ellipticity. This study may be helpful to further research done to ferrofluids and other similar colloidal samples with anisotropic optics.

Extended high circular polarization in the Orion massive star forming region: implications for the origin of homochirality in the solar system.

Science.gov (United States)

Fukue, Tsubasa; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hough, James H; Bailey, Jeremy; Whittet, Douglas C B; Lucas, Philip W; Nakajima, Yasushi; Hashimoto, Jun

2010-06-01

We present a wide-field (approximately 6' x 6') and deep near-infrared (K(s) band: 2.14 mum) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming. Our results reveal that a high circular polarization region is spatially extended (approximately 0.4 pc) around the massive star-forming region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization, in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly polarized radiation, then enantiomeric excesses could have been induced, through asymmetric photochemistry, in the parent bodies of the meteorites and subsequently delivered to Earth. These could then have played a role in the development of biological homochirality on Earth.

Omnidirectional narrow optical filters for circularly polarized light in a nanocomposite structurally chiral medium.

Science.gov (United States)

Avendaño, Carlos G; Palomares, Laura O

2018-04-20

We consider the propagation of electromagnetic waves throughout a nanocomposite structurally chiral medium consisting of metallic nanoballs randomly dispersed in a structurally chiral material whose dielectric properties can be represented by a resonant effective uniaxial tensor. It is found that an omnidirectional narrow pass band and two omnidirectional narrow band gaps are created in the blue optical spectrum for right and left circularly polarized light, as well as narrow reflection bands for right circularly polarized light that can be controlled by varying the light incidence angle and the filling fraction of metallic inclusions.

W-Band Circularly Polarized TE11 Mode Transducer

Science.gov (United States)

Zhan, Mingzhou; He, Wangdong; Wang, Lei

2018-06-01

This paper presents a balanced sidewall exciting approach to realize the circularly polarized TE11 mode transducer. We used a voltage vector transfer matrix to establish the relationship between input and output vectors, then we analyzed amplitude and phase errors to estimate the isolation of degenerate mode. A mode transducer with a sidewall exciter was designed based on the results. In the 88-100 GHz frequency range, the simulated axial ratio is less than 1.05 and the isolation of linearly polarization TE11 mode is higher than 30 dBc. In back-to-back measurements, the return loss is generally greater than 20 dB with a typical insertion loss of 1.2 dB. Back-to-back transmission measurements are in excellent agreement with simulations.

Circular polarization with crossed-planar undulators in high-gain FELs

CERN Document Server

Kim, K J K J

2000-01-01

We propose a crossed undulator configuration for a high-gain free-electron laser to allow versatile polarization control. This configuration consists of a long (saturation length) planar undulator, a dispersive section, and a short (a few gain lengths) planar undulator oriented perpendicular to the first one. In the first undulator, a radiation component linearly polarized in the x-direction is amplified to saturation. In the second undulator, the x-polarized component propagates freely, while a new component, polarized in the y-direction, is generated and reaches saturation in a few gain lengths. By adjusting the strength of the dispersive section, the relative phase of two radiation components can be adjusted to obtain a suitable polarization for the total radiation field, including the circular polarization. The operating principle of the high-gain crossed undulator, which is quite different from that of the crossed undulator for spontaneous radiation, is illustrated in terms of 1-D FEL theory.

Dual-band linearly and circularly polarized microstrip patch antennas with meandering slot and metallic vias

DEFF Research Database (Denmark)

Zhang, Jin; Lin, Xianqi; Yu, Jiawei

2018-01-01

performances. The characteristics are analyzed in detail where we find that the existence of the vias also improves the impedance matching. Four samples are designed, where dual-band with both linear polarization, dual-band with circular- and linear-polarization, and single band with linear polarization...

Simulation of generation and dynamics of polarization singularities with circular Airy beams.

Science.gov (United States)

Ye, Dong; Peng, Xinyu; Zhou, Muchun; Xin, Yu; Song, Minmin

2017-11-01

The generation and dynamics of polarization singularities have been underresearched for years, while the focusing property of the topological configuration has not been explored much. In this paper, we simulated the generation of low-order polarization singularities with a circular Airy beam and explored the focusing property of the synthetic light field during propagation due to the autofocusing of the component. Our work researched the focusing properties of the polarization singularity configuration, which may help to develop its application prospect.

Tight focusing of radially polarized circular Airy vortex beams

Science.gov (United States)

Chen, Musheng; Huang, Sujuan; Shao, Wei

2017-11-01

Tight focusing properties of radially polarized circular Airy vortex beams (CAVB) are studied numerically. The light field expressions for the focused fields are derived based on vectorial Debye theory. We also study the relationship between focal profiles, such as light intensity distribution, radius of focal spot and focal length, and the parameters of CAVB. Numerical results demonstrate that we can generate a radially polarized CAVB with super-long focal length, super-strong longitudinal intensity or subwavelength focused spot at the focal plane by properly choosing the parameters of incident light and high numerical aperture (NA) lens. These results have potential applications for optical trapping, optical storage and particle acceleration.

Design of a C- Band Circular Polarization Microstrip Antenna

Science.gov (United States)

Yohandri; Jumiah, Yusna; Tetuko Sri Sumantyo, Josaphat

2018-04-01

The development of circularly polarized microstrip antenna is an interesting topic in current research, due to its superiority in various applications. In this work, the design of a circular polarization antenna that will be operated in the C-band range will be described. The developed antenna is intended to be used for Synthetic Aperture Radar (SAR) applications. Through this application, various targets or areas on the surface of the earth, such as buildings, soil and land can be observed. To get the ideal antenna characteristic, in this research the various parameters in antenna design will be simulated. A software CST Studio will be operated in this simulation. Based on the simulation results, the optimum parameters are obtained in term of reflection coefficient, VSWR, axial ratio, and gain. The reflection coefficient of the antenna (S11) is obtained at -19.75 dB and VSWR of 1.23. Meanwhile, the axial ratio and gain of the antenna were obtained at 2.66 dB and 2.1 dBi, respectively. Based on this simulated results, antenna design is potential to be developed and fabricated for SAR sensor applications.

Emission of circularly polarized recombination radiation from p-doped GaAs and GaAs0.62P0.38 under the impact of polarized electrons

International Nuclear Information System (INIS)

Fromme, B.; Baum, G.; Goeckel, D.; Raith, W.

1989-01-01

Circularly polarized light is emitted in radiative transitions of polarized electrons from the conduction to the valence band in GaAs or GaAs 1-x P x crystals. The degree of light polarization is directly related to the polarization of the conduction-band electrons at the instant of recombination and allows conclusions about the depolarization of electrons in the conduction band. The depolarization is caused by spin-relaxation processes. The efficiency of these processes depends on crystal type, crystal temperature, degree of doping, and kinetic energy of the electrons. Highly p-doped GaAs and GaAs 0.62 P 0.38 crystals (N A >1x10 19 atoms/cm 3 ) were bombarded with polarized electrons (initial polarization 38%), and the spectral distribution and the circular polarization of the emitted recombination radiation were measured. The initial kinetic energy of the electrons in the conduction band was varied between 5 and 1000 eV. The measurements of the spectral distribution show that the electrons are thermalized before recombination occurs, independent of their initial energy. An important thermalization process in this energy range is the excitation of crystal electrons by electron-hole pair creation. The circular polarization of the recombination radiation lies below 1% in the whole energy range. It decreases with increasing electron energy but is still of measurable magnitude at 100 eV in the case of GaAs 0.62 P 0.38 . The circular polarization is smaller for GaAs than for GaAs 0.62 P 0.38 , which we attribute to more efficient spin relaxation in GaAs

Electron ionization and spin polarization control of Fe atom adsorbed graphene irradiated by a femtosecond laser

International Nuclear Information System (INIS)

Yu, Dong; Jiang, Lan; Wang, Feng; Li, Xin; Qu, Liangti; Lu, Yongfeng

2015-01-01

We investigate the structural properties and ionized spin electrons of an Fe–graphene system, in which the time-dependent density functional theory (TDDFT) within the generalized gradient approximation is used. The electron dynamics, including electron ionization and ionized electron spin polarization, is described for Fe atom adsorbed graphene under femtosecond laser irradiation. The theoretical results show that the electron ionization and ionized electron spin polarization are sensitive to the laser parameters, such as the incident angle and the peak intensity. The spin polarization presents the maximum value under certain laser parameters, which may be used as a source of spin-polarized electrons. - Highlights: • The structural properties of Fe–graphene system are investigated. • The electron dynamics of Fe–graphene system under laser irradiation are described. • The Fe–graphene system may be used as a source of spin-polarized electrons

Assessment of tissue polarimetric properties using Stokes polarimetric imaging with circularly polarized illumination.

Science.gov (United States)

Qi, Ji; He, Honghui; Lin, Jianyu; Dong, Yang; Chen, Dongsheng; Ma, Hui; Elson, Daniel S

2018-04-01

Tissue-depolarization and linear-retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here, we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular-depolarization and linear-retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry, respectively. It is found that circular-depolarization obtained from these 2 methods is very similar in both geometries, and that linear-retardance is highly quantitatively similar for transmission geometry and qualitatively similar for reflection geometry. The majority of tissue circular-depolarization and linear-retardance image information (represented by local image contrast features) obtained from Mueller polarimetry is well preserved from Stokes polarimetry in both geometries. These findings can be referred to for further understanding tissue Stokes polarimetric data, and for further application of Stokes polarimetry under the circumstances where short acquisition time or low optical system complexity is a priority, such as polarimetric endoscopy and microscopy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On-chip synthesis of circularly polarized emission of light with integrated photonic circuits.

Science.gov (United States)

He, Li; Li, Mo

2014-05-01

The helicity of circularly polarized (CP) light plays an important role in the light-matter interaction in magnetic and quantum material systems. Exploiting CP light in integrated photonic circuits could lead to on-chip integration of novel optical helicity-dependent devices for applications ranging from spintronics to quantum optics. In this Letter, we demonstrate a silicon photonic circuit coupled with a 2D grating emitter operating at a telecom wavelength to synthesize vertically emitting, CP light from a quasi-TE waveguide mode. Handedness of the emitted circular polarized light can be thermally controlled with an integrated microheater. The compact device footprint enables a small beam diameter, which is desirable for large-scale integration.

Quantitative assessment of spinal cord injury using circularly polarized coherent anti-Stokes Raman scattering microscopy

Science.gov (United States)

Bae, Kideog; Zheng, Wei; Huang, Zhiwei

2017-08-01

We report the quantitative assessment of spinal cord injury using the circularly polarized coherent anti-Stokes Raman scattering (CP-CARS) technique together with Stokes parameters in the Poincaré sphere. The pump and Stokes excitation beams are circularly polarized to suppress both the linear polarization-dependent artifacts and the nonresonant background of tissue CARS imaging, enabling quantitative CP-CARS image analysis. This study shows that CP-CARS imaging uncovers significantly increased phase retardance of injured spinal cord tissue as compared to normal tissue, suggesting that CP-CARS is an appealing label-free imaging tool for determining the degree of tissue phase retardance, which could serve as a unique diagnostic parameter associated with nervous tissue injury.

Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation.

Science.gov (United States)

Hayama, Kazuhiro; Kuroda, Takami; Nakamura, Ko; Yamada, Shoichi

2016-04-15

We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores just prior to collapse. It has been demonstrated by three dimensional simulations that nonaxisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the postbounce cores. It is not surprising, then, that the gravitational waves emitted by such fluid motions are circularly polarized. We show, in this Letter, that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of the Galaxy as long as the rotation period of the core is shorter than a few seconds prior to collapse.

Measurement of the circular polarization of gamma radiation from heavy ion collisions

International Nuclear Information System (INIS)

Lauterbach, C.

1981-01-01

For the nuclear reactions 16 O + 27 Al, 16 O + 58 Ni, 16 O + 62 Ni, 40 Ar + sup(nat)Ag, 86 Kr + sup(nat)Ag, and 86 Kr + 197 Au at incident energies of about 7 MeV/nucleon the circular polarization of the #betta# radiation emitted by the reaction products was measured. The projectile - like reaction products were detected by a δE-E telescope at a fixed angle of 35 0 relative to the beam axis. It is shown that the sign of the scattering angle for the classical orbit of the reaction partners can be determined by the experimental detection of circularly polarized #betta#-radiation from the decay of the highly excited reaction products. In the performed experiments for the first time extensive polarization phenomena in deep inelastic reactions were observed. The dominance of negative scattering angles was verified for a large range of light and medium-heavy systems. The results are compared with the predictions of theoretical models in which statistical or quantum mechanical fluctuations of the dynamical quantities are regarded. (orig./HSI) [de

Concave pulse shaping of a circularly polarized laser pulse from non-uniform overdense plasmas

Energy Technology Data Exchange (ETDEWEB)

Hur, Min Sup [School of Natural Science, UNIST, BanYeon-Ri 100, Ulju-gun, Ulsan, 689-798 (Korea, Republic of); Kulagin, Victor V. [Sternberg Astronomical Institute, Moscow State University, Universitetsky prosp. 13, Moscow, 119992 (Russian Federation); Suk, Hyyong, E-mail: hysuk@gist.ac.kr [Department of Physics and Photon Science, GIST, 123 Cheomdan-gwangiro, Buk-gu, Gwangju, 500-712 (Korea, Republic of)

2015-03-20

Pulse shaping of circularly polarized laser pulses in nonuniform overdense plasmas are investigated numerically. Specifically we show by two-dimensional particle-in-cell simulations the generation of a concave pulse front of a circularly polarized, a few tens of petawatt laser pulse from a density-tapered, overdense plasma slab. The concept used for the transverse-directional shaping is the differential transmittance depending on the plasma density, and the laser intensity. For suitable selection of the slab parameters for the concave pulse shaping, we studied numerically the pulse transmittance, which can be used for further parameter design of the pulse shaping. The concavely shaped circularly polarized pulse is expected to add more freedom in controlling the ion-beam characteristics in the RPDA regime. - Highlights: • Laser pulse shaping for a concave front by non-uniform overdense plasma was studied. • Particle-in-cell (PIC) simulations were used for the investigation. • A laser pulse can be shaped by a density-tapered overdense plasma. • The concave and sharp pulse front are useful in many laser–plasma applications. • They are important for ion acceleration, especially in the radiation pressure dominant regime.

Room-temperature single-photon sources with definite circular and linear polarizations based on single-emitter fluorescence in liquid crystal hosts

International Nuclear Information System (INIS)

Winkler, Justin M; Lukishova, Svetlana G; Bissell, Luke J

2013-01-01

Definite circular and linear polarizations of room-temperature single-photon sources, which can serve as polarization bases for quantum key distribution, are produced by doping planar-aligned liquid crystal hosts with single fluorescence emitters. Chiral 1-D photonic bandgap microcavities for a single handedness of circularly polarized light were prepared from both monomeric and oligomeric cholesteric liquid crystals. Fluorescent emitters, such as nanocrystal quantum dots, nitrogen vacancy color centers in nanodiamonds, and rare-earth ions in nanocrystals, were doped into these microcavity structures and used to produce circularly polarized fluorescence of definite handedness. Additionally, we observed circularly polarized resonances in the spectrum of nanocrystal quantum dot fluorescence at the edge of the cholesteric microcavity's photonic stopband. For this polarization we obtained a ∼4.9 enhancement of intensity compared to the polarization of the opposite handedness that propagates without photonic bandgap microcavity effects. Such a resonance is indicative of coupling of quantum dot fluorescence to the cholesteric microcavity mode. We have also used planar-aligned nematic liquid crystal hosts to align DiI dye molecules doped into the host, thereby providing a single-photon source of linear polarization of definite direction. Antibunching is demonstrated for fluorescence of nanocrystal quantum dots, nitrogen vacancy color centers, and dye molecules in these liquid crystal structures.

Multiphoton ionization of the hydrogen atom by a circularly polarized electromagnetic field

International Nuclear Information System (INIS)

Prepelitsa, O.B.

1999-01-01

This paper examines the multiphoton ionization of the ground state of the hydrogen atom in the field of a circularly polarized intense electromagnetic wave. To describe the states of photoelectrons, quasiclassical wave functions are introduced that partially allow for the effect of an intense electromagnetic wave and that of the Coulomb potential. Expressions are derived for the angular and energy distributions of photoelectrons with energies much lower than the ionization potential of an unperturbed atom. It is found that, due to allowance for the Coulomb potential in the wave function of the final electron states, the transition probability near the ionization threshold tends to a finite value. In addition, the well-known selection rules for multiphoton transitions in a circularly polarized electromagnetic field are derived in a natural way. Finally, the results are compared with those obtained in the Keldysh-Faisal-Reiss approximation

Femtosecond laser inscribed cladding waveguide lasers in Nd:LiYF4 crystals

Science.gov (United States)

Li, Shi-Ling; Huang, Ze-Ping; Ye, Yong-Kai; Wang, Hai-Long

2018-06-01

Depressed circular cladding, buried waveguides were fabricated in Nd:LiYF4 crystals with an ultrafast Yb-doped fiber master-oscillator power amplifier laser. Waveguides were optimized by varying the laser writing conditions, such as pulse energy, focus depth, femtosecond laser polarization and scanning velocity. Under optical pump at 799 nm, cladding waveguides showed continuous-wave laser oscillation at 1047 nm. Single- and multi-transverse modes waveguide laser were realized by varying the waveguide diameter. The maximum output power in the 40 μm waveguide is ∼195 mW with a slope efficiency of 34.3%. The waveguide lasers with hexagonal and cubic cladding geometry were also realized.

A Study of the use of a Crystal as a `Quarter-Wave Plate' to Produce High Energy Circularly Polarized Photons

CERN Multimedia

Kononets, I

2002-01-01

%NA59 %title\\\\ \\\\We present a proposal to study the use of a crystal as a `quarter-wave plate' to produce high energy circularly polarized photons, starting from unpolarized electrons. The intention is to generate linearly polarized photons by letting electrons pass a crystalline target, where they interact coherently with the lattice nuclei. The photon polarization is subsequently turned into circular polarization after passing another crystal, which acts as a `quarter-wave plate'.

Multiphoton processes in the field of two-frequency circularly polarized plane electromagnetic waves

International Nuclear Information System (INIS)

Yu, An

1997-01-01

The authors solve Dirac's equation for an electron in the field of a two-frequency plane electromagnetic wave, deriving general formulae for the probabilities of radiation of a photon by the electron, and for the probabilities for pair production by a photon when the two-frequency wave is circularly polarized. In contrast to the case of a monochromatic-plane electromagnetic wave, when an electron is in the field of a two-frequency circularly polarized wave, besides the absorption of multiphotons and emission of simple harmonics of the individual waves, stimulated multiphoton emission processes and various composite harmonic-photon emission processes are occurred: when a high-energy photon is in a such a field, multiphoton processes also follow the pair production processes

Classical origins of stabilization in circularly polarized laser fields

International Nuclear Information System (INIS)

Chism, Will; Choi, Dae-Il; Reichl, L. E.

2000-01-01

We investigate the interaction of a two-dimensional model atom with an intense, high-frequency circularly polarized laser pulse. As the laser intensity is increased, the ionization rate initially increases, then decreases dramatically, with the electron wave function developing an asymmetric ring form which rotates with the electric field. We provide evidence that this wave form is due to localization of the electron onto nonlinear classical structures. (c) 2000 The American Physical Society

Plasmon-mediated circularly polarized luminescence of GaAs in a scanning tunneling microscope

Energy Technology Data Exchange (ETDEWEB)

Mühlenberend, Svenja; Gruyters, Markus; Berndt, Richard, E-mail: berndt@physik.uni-kiel.de [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel (Germany)

2015-12-14

The electroluminescence from p-type GaAs(110) in a scanning tunneling microscope has been investigated at 6 K. Unexpectedly, high degrees of circular polarization have often been observed with ferromagnetic Ni tips and also with paramagnetic W and Ag tips. The data are interpreted in terms of two distinct excitation mechanisms. Electron injection generates intense luminescence with low polarization. Plasmon-mediated generation of electron-hole pairs leads to less intense emission, which, however, is highly polarized for many tips.

Two-color stabilization of atomic hydrogen in circularly polarized laser fields

International Nuclear Information System (INIS)

Bauer, D.; Ceccherini, F.

2002-01-01

The dynamic stabilization of atomic hydrogen against ionization in high-frequency single- and two-color, circularly polarized laser pulses is observed by numerically solving the three-dimensional, time-dependent Schroedinger equation. The single-color case is revisited and numerically determined ionization rates are compared with both, the exact and the approximate high-frequency Floquet rates. The positions of the peaks in the photoelectron spectra can be explained with the help of dressed initial states. In two-color laser fields of opposite circular polarization, the stabilized probability density may be shaped in various ways. For laser frequencies ω 1 and ω 2 =nω 1 , n=2,3,..., and sufficiently large excursion amplitudes (n+1) distinct probability density peaks are observed. This may be viewed as the generalization of the well-known 'dichotomy' in linearly polarized laser fields, i.e, as 'trichotomy', 'quatrochotomy', 'pentachotomy' etc. All those observed structures and their 'hula-hoop'-like dynamics can be understood with the help of high-frequency Floquet theory and the two-color Kramers-Henneberger transformation. The shaping of the probability density in the stabilization regime can be realized without additional loss in the survival probability, as compared to the corresponding single-color results

Frenkel-exciton decomposition analysis of circular dichroism and circularly polarized luminescence for multichromophoric systems.

Science.gov (United States)

Shiraogawa, Takafumi; Ehara, Masahiro; Jurinovich, Sandro; Cupellini, Lorenzo; Mennucci, Benedetta

2018-06-15

Recently, a method to calculate the absorption and circular dichroism (CD) spectra based on the exciton coupling has been developed. In this work, the method was utilized for the decomposition of the CD and circularly polarized luminescence (CPL) spectra of a multichromophoric system into chromophore contributions for recently developed through-space conjugated oligomers. The method which has been implemented using rotatory strength in the velocity form and therefore it is gauge-invariant, enables us to evaluate the contribution from each chromophoric unit and locally excited state to the CD and CPL spectra of the total system. The excitonic calculations suitably reproduce the full calculations of the system, as well as the experimental results. We demonstrate that the interactions between electric transition dipole moments of adjacent chromophoric units are crucial in the CD and CPL spectra of the multichromophoric systems, while the interactions between electric and magnetic transition dipole moments are not negligible. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Minimum Q circularly polarized electrically small spherical antennas

DEFF Research Database (Denmark)

Kim, Oleksiy S.

2011-01-01

The radiation problem for the TM10- and TE10-mode electric current densities on the surface of a spherical magnetic-coated PEC core is solved analytically. The combination of the electric and magnetic dipole modes reduces the radiation Q of the antenna. Moreover, with an appropriately designed...... magnetic-coated PEC core the stored energies of these modes balance each other making the antenna self-resonant and at the same time ensuring a perfect circularly polarized radiation. Numerical results for a practical dual-mode electrically small antenna confirm the theoretical predictions. A 4-arm...

Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

Directory of Open Access Journals (Sweden)

Kai-Jun Yuan

2015-01-01

Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

Dynamical model of coherent circularly polarized optical pulse interactions with two-level quantum systems

International Nuclear Information System (INIS)

Slavcheva, G.; Hess, O.

2005-01-01

We propose and develop a method for theoretical description of circularly (elliptically) polarized optical pulse resonant coherent interactions with two-level atoms. The method is based on the time-evolution equations of a two-level quantum system in the presence of a time-dependent dipole perturbation for electric dipole transitions between states with total angular-momentum projection difference (ΔJ z =±1) excited by a circularly polarized electromagnetic field [Feynman et al., J. Appl. Phys. 28, 49 (1957)]. The adopted real-vector representation approach allows for coupling with the vectorial Maxwell's equations for the optical wave propagation and thus the resulting Maxwell pseudospin equations can be numerically solved in the time domain without any approximations. The model permits a more exact study of the ultrafast coherent pulse propagation effects taking into account the vector nature of the electromagnetic field and hence the polarization state of the optical excitation. We demonstrate self-induced transparency effects and formation of polarized solitons. The model represents a qualitative extension of the well-known optical Maxwell-Bloch equations valid for linearly polarized light and a tool for studying coherent quantum control mechanisms

Analysis of Circularly Polarized Hemispheroidal Dielectric Resonator Antenna Phased Arrays Using the Method of Auxiliary Sources

DEFF Research Database (Denmark)

Larsen, Niels Vesterdal; Breinbjerg, Olav

2007-01-01

The method of auxiliary sources is employed to model and analyze probe-fed hemispheroidal dielectric resonator antennas and arrays. Circularly polarized antenna elements of different designs are analyzed, and impedance bandwidths of up to 14.7% are achieved. Selected element designs are subsequen......The method of auxiliary sources is employed to model and analyze probe-fed hemispheroidal dielectric resonator antennas and arrays. Circularly polarized antenna elements of different designs are analyzed, and impedance bandwidths of up to 14.7% are achieved. Selected element designs...

Circularly polarized harmonic generation by intense bicircular laser pulses: electron recollision dynamics and frequency dependent helicity

Science.gov (United States)

Bandrauk, André D.; Mauger, François; Yuan, Kai-Jun

2016-12-01

Numerical solutions of time-dependent Schrödinger equations for one and two electron cyclic molecules {{{H}}}nq+ exposed to intense bichromatic circularly polarized laser pulses of frequencies {ω }1 and {ω }2, such that {ω }1/{ω }2={n}1/{n}2 (integer) produce circularly polarized high order harmonics with a cut-off recollision maximum energy at and greater than the linear polarization law (in atomic units) {N}m{ω }1={I}p+3.17{U}p, where I p is the ionization potential and {U}p={(2{E}0)}2/4{ω }2 is the ponderomotive energy defined by the field E 0 (intensity I={{cE}}02/8π ) from each pulse and mean frequency ω =({ω }1+{ω }2)/2 . An electron recollision model in a rotating frame at rotating frequency {{Δ }}ω =({ω }1-{ω }2)/2 predicts this simple result as a result of recollision dynamics in a combination of bichromatic circularly polarized pulses. The harmonic helicities and their intensities are shown to depend on compatible symmetries of the net pulse electric fields with that of the molecules.

State preparation and detector effects in quantum measurements of rotation with circular polarization-entangled photons and photon counting

Science.gov (United States)

Cen, Longzhu; Zhang, Zijing; Zhang, Jiandong; Li, Shuo; Sun, Yifei; Yan, Linyu; Zhao, Yuan; Wang, Feng

2017-11-01

Circular polarization-entangled photons can be used to obtain an enhancement of the precision in a rotation measurement. In this paper, the method of entanglement transformation is used to produce NOON states in circular polarization from a readily generated linear polarization-entangled photon source. Detection of N -fold coincidences serves as the postselection and N -fold superoscillating fringes are obtained simultaneously. A parity strategy and conditional probabilistic statistics contribute to a better fringe, saturating the angle sensitivity to the Heisenberg limit. The impact of imperfect state preparation and detection is discussed both separately and jointly. For the separated case, the influence of each system imperfection is pronounced. For the joint case, the feasibility region for surpassing the standard quantum limit is given. Our work pushes the state preparation of circular polarization-entangled photons to the same level as that in the case of linear polarization. It is also confirmed that entanglement can be transformed into different frames for specific applications, serving as a useful scheme for using entangled sources.

Circularly Polarized Antenna Array Fed by Air-Bridge Free CPW-Slotline Network

Directory of Open Access Journals (Sweden)

Yilin Liu

2017-01-01

Full Text Available A novel design of 1×2 and 2×2 circularly polarized (CP microstrip patch antenna arrays is presented in this paper. The two CP antenna arrays are fed by sequentially rotated coplanar waveguide (CPW to slotline networks and are processed on 1 mm thick single-layer FR4 substrates. Both of the two arrays are low-profile and lightweight. An air-bridge free CPW-slotline power splitter is appropriately designed to form the feeding networks and realize the two CP antenna arrays. The mechanism of circular polarization in this design is explained. The simulated and measured impedance bandwidths as well as the 3 dB axial ratio bandwidths and the radiation patterns of the two proposed antenna arrays are presented. This proposed design can be easily extended to form a larger plane array with good performance owing to its simple structure.

Angular momentum of circularly polarized light in dielectric media

OpenAIRE

Mansuripur, Masud

2014-01-01

A circularly polarized plane-wave is known to have no angular momentum when examined through Maxwell's equations. This, however, contradicts the experimentally observed facts, where finite segments of plane waves are known to be capable of imparting angular momentum to birefringent platelets. Using a superposition of four plane-waves propagating at slightly different angles to a common direction, we derive an expression for the angular momentum density of a single plane-wave in the limit when...

Circular motion of particles suspended in a Gaussian beam with circular polarization validates the spin part of the internal energy flow

DEFF Research Database (Denmark)

Angelsky, O. V.; Bekshaev, A. Ya.; Maksimyak, P. P.

2012-01-01

switching to the right (left) circular polarization, the particles performed spinning motion in agreement with the angular momentum imparted by the field, but they were involved in an orbital rotation around the beam axis as well, which in previous works [Y. Zhao et al, Phys. Rev. Lett. 99, 073901 (2007......Non-spherical dielectric microparticles were suspended in a water-filled cell and exposed to a coherent Gaussian light beam with controlled state of polarization. When the beam polarization is linear, the particles were trapped at certain off-axial position within the beam cross section. After...... of inhomogeneously polarized paraxial beams [A. Bekshaev et al, J. Opt. 13, 053001 (2011)]....

Absorption of circularly polarized light by solids

International Nuclear Information System (INIS)

Jalbert, G.; Brandi, H.S.

1984-03-01

The multiphoton absorption rate of circularly polarized light, by direct gap crystals, was investigated following a non-perturbative scheme proposed by Jones and Reiss. It was possible to derive closed analytical solutions, for the N-photon transition rate, valid for all field strenghts of practical interest. The accuracy of the approximations introduced in deriving these results was determined comparing the numerical computations of the multiphoton transition rate ('exact') with the analytical solutions. Specific calculations are done for ZnS and GaAs in the presence of a Nd-laser. It is shown that this formalism leads to a total transition rate which has not the tunneling behavior previously discussed by several authors within similar contexts. (Author) [pt

Attosecond polarization control in atomic RABBITT-like experiments assisted by a circularly polarized laser

Science.gov (United States)

Boll, D. I. R.; Fojón, O. A.

2017-12-01

We study theoretically the single ionization of noble gas atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. We employ a non-perturbative model that under certain approximations gives closed-form expressions for the angular distributions of photoelectrons. Interestingly, our model allow us to interpret these angular distributions as two-centre interferences where the orientation and the modulus of the separation vector between the virtual emitters is governed by the assistant laser field. Additionally, we show that such a configuration of light fields is similar to the polarization control technique, where both the attosecond pulse train and the assistant laser field have linear polarizations whose relative orientation may be controlled. Moreover, in order to compare our results with the available experimental data, we obtain analytical expressions for the cross sections integrated over the photoelectron emission angles. By means of these expressions, we define the ‘magic time’ as the delay for which the total cross sections for atomic targets exhibit the same functional form as the one of the monochromatic photoionization of diatomic molecular targets.

CORPORATE FEED WITH DUAL SEGMENT CIRCULAR POLARIZED ARRAY RECTENNA FOR LOW POWER RF ENERGY HARVESTING

Directory of Open Access Journals (Sweden)

CHIA CHAO KANG

2016-06-01

Full Text Available This paper focuses on the investigation of the level powers that can be scavenged from the ambient environment by using corporate feed with dual segment circular polarized antenna array . It will converts the received power to direct current (DC. Being a circular polarized antenna, it has higher inductance per unit area, a good Q-factor and compact capability. The design of corporate-series feed rectenna array is to achieve a high gain antenna and maximize the RF energy received by the rectenna system at ultra low power levels. The entire structure was investigated using a combination of harmonic balance nonlinear analysis and full wave electromagnetic field analysis. The results show that 5.0 dBi gain for circular polarized antenna array can be achieved at frequency 956 MHz. When the input power of 20 dBm fed into the transmitting antenna, the maximum distance for radio frequency (RF harvesting is 5.32m. The output DC voltage for various values of incident RF power is also presented. There are noticed reasonable agreements between the simulated and measured result and the works concludes that the investigation of RF energy harvesting system was successful.

Detecting primordial gravitational waves with circular polarization of the redshifted 21 cm line. I. Formalism

Science.gov (United States)

Hirata, Christopher M.; Mishra, Abhilash; Venumadhav, Tejaswi

2018-05-01

We propose a new method to measure the tensor-to-scalar ratio r using the circular polarization of the 21 cm radiation from the pre-reionization epoch. Our method relies on the splitting of the F =1 hyperfine level of neutral hydrogen due to the quadrupole moment of the cosmic microwave background (CMB). We show that unlike the Zeeman effect, where MF=±1 have opposite energy shifts, the CMB quadrupole shifts MF=±1 together relative to MF=0 . This splitting leads to a small circular polarization of the emitted 21 cm radiation. In this paper (Paper I in a series on this effect), we present calculations on the microphysics behind this effect, accounting for all processes that affect the hyperfine transition. We conclude with an analytic formula for the circular polarization from the Dark Ages as a function of pre-reionization parameters and the value of the remote quadrupole of the CMB. We also calculate the splitting of the F =1 hyperfine level due to other anisotropic radiation sources and show that they are not dominant. In a companion paper (Paper II) we make forecasts for measuring the tensor-to-scalar ratio r using future radio arrays.

Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

Science.gov (United States)

Greem. David; DuToit, Cornelis

2013-01-01

The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

Rotated infrared antenna transmitarray for the manipulation of circularly polarized wavefronts

Directory of Open Access Journals (Sweden)

He Yuchu

2014-01-01

Full Text Available An IR optical transmitarray is presented based on Antenna Array Sheet (AAS for the manipulation of circularly polarized light. The unit cell of the transmitarray comprises three layers of metallic elliptical patches. Complete phase control is achieved through the local rotation of each unit cell. Thin refraction and focusing transmitarrays of this sort are demonstrated at infrared frequencies. Moreover, a new concept for realizing a polarization-discriminating device is introduced based on a flat refracting lens. These devices are compatible with current fabrication technology and can become crucial for the integration with other IR and nano-photonic devices.

Phase dispersion of Raman and Rayleigh-enhanced four-wave mixings in femtosecond polarization beats

International Nuclear Information System (INIS)

Yan, Zhao; Zhi-Qiang, Nie; Chang-Biao, Li; Yan-Peng, Zhang; Chen-Li, Gan; Huai-Bin, Zheng; Yuan-Yuan, Li; Ke-Qing, Lu

2009-01-01

Based on color-locking noisy field correlation in three Markovian stochastic models, phase dispersions of the Raman- and Rayleigh-enhanced four-wave mixing (FWM) have been investigated. The phase dispersions are modified by both linewidth and time delay for negative time delay, but only by linewidth for positive time delay. Moreover, the results under narrowband condition are close to the nonmodified nonlinear dispersion and absorption of the material. Homodyne and heterodyne detections of the Raman, the Rayleigh and the mixing femtosecond difference-frequency polarization beats have also been investigated, separately

DOA and Polarization Estimation Using an Electromagnetic Vector Sensor Uniform Circular Array Based on the ESPRIT Algorithm.

Science.gov (United States)

Wu, Na; Qu, Zhiyu; Si, Weijian; Jiao, Shuhong

2016-12-13

In array signal processing systems, the direction of arrival (DOA) and polarization of signals based on uniform linear or rectangular sensor arrays are generally obtained by rotational invariance techniques (ESPRIT). However, since the ESPRIT algorithm relies on the rotational invariant structure of the received data, it cannot be applied to electromagnetic vector sensor arrays (EVSAs) featuring uniform circular patterns. To overcome this limitation, a fourth-order cumulant-based ESPRIT algorithm is proposed in this paper, for joint estimation of DOA and polarization based on a uniform circular EVSA. The proposed algorithm utilizes the fourth-order cumulant to obtain a virtual extended array of a uniform circular EVSA, from which the pairs of rotation invariant sub-arrays are obtained. The ESPRIT algorithm and parameter pair matching are then utilized to estimate the DOA and polarization of the incident signals. The closed-form parameter estimation algorithm can effectively reduce the computational complexity of the joint estimation, which has been demonstrated by numerical simulations.

A Low-Profile Dual-Layer Patch Antenna with a Circular Polarizer Consisting of Dual Semicircular Resonators

Directory of Open Access Journals (Sweden)

Li Guo

2018-06-01

Full Text Available In this paper, a circular polarizer comprising dual semicircular split-rings (DSSRs is presented. By placing it above an elliptical radiator that radiates linearly polarized (LP waves, dual-layer patch antennas capable of radiating right-hand (RH or left-hand (LH circularly polarized (CP waves are achieved in terms of the different offset direction of the bottom splits of the DSSRs. Because of both the capacitive coupling to the radiator and the degenerate modes existing in the excited DSSRs, the DSSRs collaboratively result in a circularly polarized radiation, successfully converting incident LP waves into CP ones. Simulated results show that the impedance, axial ratio (AR, and gain frequency response of both proposed CP antennas are identical, with a simulated 3-dB AR bandwidth of 72 MHz covering 2.402–2.474 GHz and a gain enhanced by 3.9 dB. The proposed antennas were fabricated and measured, revealing an operational bandwidth of 65 MHz (2.345–2.41 GHz and a peak gain up to 9 dBi. Moreover, a low profile of 0.063λ0 is maintained. The proposed CP antennas could be as a candidate for wireless target detection applications in terms of their identical frequency response property.

Circular polarization of γ-quanta radiated in the capture of polarized neutrons by protons and the quark compound bag model

International Nuclear Information System (INIS)

Grach, I.L.; Shmatkov, M.Zh.

1983-01-01

The circular polarization Psub(γ) of γ-quanta radiated in the capture of polarized neutrons by protons is calculated The contribution of the M1 and E2 radiation of nucleons to Psub(γ) is found using the accurate wave functions of the continuous spectrum. The contribution of the six-quark bag to the polarization Psub(γ) is determined. The value of Psub(γ) is related to the admixture of the 6q-bag in the deuteron. Experimental value of Psub(γ) corresponds to small (< or approximately 0.7%) admixture of the bag

Interpreting tunneling time in circularly polarized strong-laser ionization

OpenAIRE

Yuan, MingHu; Xin, PeiPei; Chu, TianShu; Liu, HongPing

2016-01-01

We propose a method to study the tunneling process by analyzing the time-dependent ionization yield in circularly polarized laser. A numerical calculation shows that for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs. the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obviou...

Circularly-polarized, semitransparent and double-sided holograms based on helical photonic structures.

Science.gov (United States)

Kobashi, Junji; Yoshida, Hiroyuki; Ozaki, Masanori

2017-11-28

Recent advances in nanofabrication techniques are opening new frontiers in holographic devices, with the capability to integrate various optical functions in a single device. However, while most efficient holograms are achieved in reflection-mode configurations, they are in general opaque because of the reflective substrate that must be used, and therefore, have limited applicability. Here, we present a semi-transparent, reflective computer-generated hologram that is circularly-polarization dependent, and reconstructs different wavefronts when viewed from different sides. The integrated functionality is realized using a single thin-film of liquid crystal with a self-organized helical structure that Bragg reflects circularly-polarized light over a certain band of wavelengths. Asymmetry depending on the viewing side is achieved by exploiting the limited penetration depth of light in the helical structure as well as the nature of liquid crystals to conform to different orientational patterns imprinted on the two substrates sandwiching the material. Also, because the operation wavelength is determined by the reflection band position, pseudo-color holograms can be made by simply stacking layers with different designs. The unique characteristics of this hologram may find applications in polarization-encoded security holograms and see-through holographic signage where different information need to be displayed depending on the viewing direction.

An offset-fed 20/30 GHz dual-band circularly polarized reflectarray antenna

DEFF Research Database (Denmark)

Smith, Thomas Gunst; Vesterdal, Niels; Gothelf, Ulrich

2013-01-01

A dual-frequency circularly polarized offset reflectarray antenna for Ka-band satellite communication is presented. The reflectarray is designed using the concentric dual split-loop element which enables full 360° phase adjustment simultaneously in two separate frequency bands. The elements have...... been optimized to suppress the cross-polar reflection. Thereafter, the element data is used for synthesis of the reflectarray layout and computation of the associated radiation patterns. The reflectarray is 400mm × 400mm and radiates LHCP at 19.95 GHz and RHCP at 29.75 GHz. Aperture efficiencies of 58......% and 60% are obtained at these frequencies, and the cross-polarization is more than 25 dB below peak gain....

A solid-state dedicated circularly polarized luminescence spectrophotometer: Development and application.

Science.gov (United States)

Harada, Takunori; Hayakawa, Hiroshi; Watanabe, Masayuki; Takamoto, Makoto

2016-07-01

A new solid-state dedicated circularly polarized luminescence (CPL) instrument (CPL-200CD) was successfully developed for measuring true CPL spectra for optically anisotropic samples on the basis of the Stokes-Mueller matrix approach. Electric components newly installed in the CPL-200CD include a pulse motor-driven sample rotation holder and a 100 kHz lock-in amplifier to achieve the linearly polarized luminescence measurement, which is essential for obtaining the true CPL signal for optically anisotropic samples. An acquisition approach devised for solid-state CPL analysis reduces the measurement times for a data set by ca. 98% compared with the time required in our previous method. As a result, the developed approach is very effective for samples susceptible to light-induced degradation. The theory and implementation of the method are described, and examples of its application to a CPL sample with macroscopic anisotropies are provided. An important advantage of the developed instrument is its ability to obtain molecular information for both excited and ground states because circular dichroism measurements can be performed by switching the monochromatic light to white light without rearrangement of the sample.

SEARCH FOR A MAGNETIC FIELD VIA CIRCULAR POLARIZATION IN THE WOLF-RAYET STAR EZ CMa

International Nuclear Information System (INIS)

De la Chevrotière, A.; St-Louis, N.; Moffat, A. F. J.

2013-01-01

We report on the first deep, direct search for a magnetic field via the circular polarization of Zeeman splitting in a Wolf-Rayet (W-R) star. Using the highly efficient ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, we observed at three different epochs one of the best W-R candidates in the sky expected to harbor a magnetic field, the bright, highly variable WN4 star EZ CMa = WR6 = HD 50896. We looked for the characteristic circular polarization (Stokes V) pattern in strong emission lines that would arise as a consequence of a global, rotating magnetic field with a split monopole configuration. We also obtained nearly simultaneous linear polarization spectra (Stokes Q and U), which are dominated by electron scattering, most likely from a flattened wind with large-scale corotating structures. As the star rotates with a period of 3.766 days, our view of the wind changes, which in turn affects the value of the linear polarization in lines versus continuum at the ∼0.2% level. Depending on the epoch of observation, our Stokes V data were affected by significant crosstalk from Stokes Q and U to V. We removed this spurious signal from the circular polarization data and experimented with various levels of spectral binning to increase the signal-to-noise ratio of our data. In the end, no magnetic field is unambiguously detected in EZ CMa. Assuming that the star is intrinsically magnetic and harbors a split monopole configuration, we find an upper limit of B ∼ 100 G for the intensity of its field in the line-forming regions of the stellar wind.

SEARCH FOR A MAGNETIC FIELD VIA CIRCULAR POLARIZATION IN THE WOLF-RAYET STAR EZ CMa

Energy Technology Data Exchange (ETDEWEB)

De la Chevrotiere, A.; St-Louis, N.; Moffat, A. F. J. [Departement de Physique, Universite de Montreal and Centre de Recherche en Astrophysique du Quebec (CRAQ), C. P. 6128, succ. centre-ville, Montreal (Quebec) H3C 3J7 (Canada); Collaboration: MiMeS Collaboration

2013-02-20

We report on the first deep, direct search for a magnetic field via the circular polarization of Zeeman splitting in a Wolf-Rayet (W-R) star. Using the highly efficient ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, we observed at three different epochs one of the best W-R candidates in the sky expected to harbor a magnetic field, the bright, highly variable WN4 star EZ CMa = WR6 = HD 50896. We looked for the characteristic circular polarization (Stokes V) pattern in strong emission lines that would arise as a consequence of a global, rotating magnetic field with a split monopole configuration. We also obtained nearly simultaneous linear polarization spectra (Stokes Q and U), which are dominated by electron scattering, most likely from a flattened wind with large-scale corotating structures. As the star rotates with a period of 3.766 days, our view of the wind changes, which in turn affects the value of the linear polarization in lines versus continuum at the {approx}0.2% level. Depending on the epoch of observation, our Stokes V data were affected by significant crosstalk from Stokes Q and U to V. We removed this spurious signal from the circular polarization data and experimented with various levels of spectral binning to increase the signal-to-noise ratio of our data. In the end, no magnetic field is unambiguously detected in EZ CMa. Assuming that the star is intrinsically magnetic and harbors a split monopole configuration, we find an upper limit of B {approx} 100 G for the intensity of its field in the line-forming regions of the stellar wind.

Femtosecond pulse shaping using plasmonic snowflake nanoantennas

Energy Technology Data Exchange (ETDEWEB)

Tok, Ruestue Umut; Sendur, Kuersat [Sabanci University, Orhanli-Tuzla, 34956, Istanbul (Turkey)

2011-09-15

We have theoretically demonstrated femtosecond pulse manipulation at the nanoscale using the plasmonic snowflake antenna's ability to localize light over a broad spectrum. To analyze the interaction of the incident femtosecond pulse with the plasmonic nanoantenna, we first decompose the diffraction limited incident femtosecond pulse into its spectral components. The interaction of each spectral component with the nanoantenna is analyzed using finite element technique. The time domain response of the plasmonic antenna is obtained using inverse Fourier transformation. It is shown that the rich spectral characteristics of the plasmonic snowflake nanoantenna allow manipulation of the femtosecond pulses over a wide spectrum. Light localization around the gap region of the nanoantenna is shown for femtosecond pulses. As the alignment of incident light polarization is varied, different antenna elements oscillate, which in turn creates a different spectrum and a distinct femtosecond response.

Low-Cost and High-Gain SIW Circularly Polarized Circular-Horn-Loaded Antenna for Broadband Millimeter-Wave Applications

Directory of Open Access Journals (Sweden)

Ming Du

2017-09-01

Full Text Available A wideband, low-cost and high-gain circularly polarized (CP circular-horn-loaded antenna based on substrate integrated waveguide (SIW technology operating at Ka band is presented. The proposed antenna, which is built on a single-layer substrate, consists of five parts: a short-ended SIW, a centro-symmetric wide slot, an L-shaped probe, a circular horn and a transition from SIW to air-filled rectangular waveguide for measurement. The slot is etched on the upper ground of the SIW, while the L-shaped probe for generating CP wave is printed inside the slot and connected to the SIW. A circular horn is also loaded on the surface of the SIW slot for high gain. Then, the proposed antenna with a dimension of 45×45×24.16 mm3 was fabricated and measured. The measured results show that the antenna has a wide impedance matching bandwidth of 28.6% from 30 to 40 GHz for |S11| ≤10 dB and a wide axial ratio (AR bandwidth of 22.8% from 31.5 to 39.6 GHz for AR ≤ 3 dB. The measured maximum gain is 15.6 dBi at 36 GHz with slight fluctuations over the 30–40-GHz frequency range. This kind of antenna merits low cost and easy integration with common differential circuits at the same time.

Plasmon mediated non-photochemical nucleation of nanoparticles by circularly polarized light

OpenAIRE

Karpov, Victor G.; Grigorchuk, Nicholas I.

2014-01-01

We predict nucleation of pancake shaped metallic nanoparticles having plasmonic frequencies in resonance with a non-absorbed circularly polarized electromagnetic field. We show that the same field can induce nucleation of randomly oriented needle shaped particles. The probabilities of these shapes are estimated vs. field frequency and strength, material parameters, and temperature. This constitutes a quantitative model of non-photochemical laser induced nucleation (NPLIN) consistent with the ...

Intense field stabilization in circular polarization: Three-dimensional time-dependent dynamics

International Nuclear Information System (INIS)

Choi, Dae-Il; Chism, Will

2002-01-01

We investigate the stabilization of hydrogen atoms in a circularly polarized laser field. We use a three-dimensional, time-dependent approach to study the quantum dynamics of hydrogen atoms subject to high-intensity, short-wavelength, laser pulses. We find an enhanced survival probability as the field is increased under fixed envelope conditions. We also confirm wave packet behaviors previously seen in two-dimensional time-dependent computations

Steady state ion acceleration by a circularly polarized laser pulse

International Nuclear Information System (INIS)

Zhang Xiaomei; Shen Baifei; Cang Yu; Li Xuemei; Jin Zhangying; Wang Fengchao

2007-01-01

The steady state ion acceleration at the front of a cold solid target by a circularly polarized flat-top laser pulse is studied with one-dimensional particle-in-cell (PIC) simulation. A model that ions are reflected by a steady laser-driven piston is used by comparing with the electrostatic shock acceleration. A stable profile with a double-flat-top structure in phase space forms after ions enter the undisturbed region of the target with a constant velocity

Controlling electron quantum paths for generation of circularly polarized high-order harmonics by H2+ subject to tailored (ω , 2 ω ) counter-rotating laser fields

Science.gov (United States)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2018-04-01

Recently, studies of high-order harmonics (HHG) from atoms driven by bichromatic counter-rotating circularly polarized laser fields as a source of coherent circularly polarized extreme ultraviolet (XUV) and soft-x-ray beams in a tabletop-scale setup have received considerable attention. Here, we demonstrate the ability to control the electron recollisions giving three returns per one cycle of the fundamental frequency ω by using tailored bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields with a molecular target. The full control of the electronic pathway is first analyzed by a classical trajectory analysis and then extended to a detailed quantum study of H2+ molecules in bichromatic (ω , 2 ω ) counter-rotating circularly polarized laser fields. The radiation spectrum contains doublets of left- and right-circularly polarized harmonics in the XUV ranges. We study in detail the below-, near-, and above-threshold harmonic regions and describe how excited-state resonances alter the ellipticity and phase of the generated harmonic peaks.

Applications of circularly polarized photons at the ALS with a bend magnet source

International Nuclear Information System (INIS)

1992-02-01

The purpose of this workshop is to focus attention on, and to stimulate the scientific exploitation of, the natural polarization properties of bend-magnet synchrotron radiation at the ALS -- for research in biology, materials science, physics, and chemistry. The topics include: The Advanced Light Source; Magnetic Circular Dichroism and Differential Scattering on Biomolecules; Tests of Fundamental Symmetries; High T c Superconductivity; Photoemission from Magnetic and Non-magnetic Solids; Studies of Highly Correlated Systems; and Instrumentation for Photon Transport and Polarization Measurements

Research of the impact of coupling between unit cells on performance of linear-to-circular polarization conversion metamaterial with half transmission and half reflection

Science.gov (United States)

Guo, Mengchao; Zhou, Kan; Wang, Xiaokun; Zhuang, Haiyan; Tang, Dongming; Zhang, Baoshan; Yang, Yi

2018-04-01

In this paper, the impact of coupling between unit cells on the performance of linear-to-circular polarization conversion metamaterial with half transmission and half reflection is analyzed by changing the distance between the unit cells. An equivalent electrical circuit model is then built to explain it based on the analysis. The simulated results show that, when the distance between the unit cells is 23 mm, this metamaterial converts half of the incident linearly-polarized wave into reflected left-hand circularly-polarized wave and converts the other half of it into transmitted left-hand circularly-polarized wave at 4.4 GHz; when the distance is 28 mm, this metamaterial reflects all of the incident linearly-polarized wave at 4.4 GHz; and when the distance is 32 mm, this metamaterial converts half of the incident linearly-polarized wave into reflected right-hand circularly-polarized wave and converts the other half of it into transmitted right-hand circularly-polarized wave at 4.4 GHz. The tunability is realized successfully. The analysis shows that the changes of coupling between unit cells lead to the changes of performance of this metamaterial. The coupling between the unit cells is then considered when building the equivalent electrical circuit model. The built equivalent electrical circuit model can be used to perfectly explain the simulated results, which confirms the validity of it. It can also give help to the design of tunable polarization conversion metamaterials.

A Circular Polarized Rectenna with Out-of-Band Suppression for Microwave Power Transmission

Directory of Open Access Journals (Sweden)

Weijun Hong

2016-01-01

Full Text Available A novel circular polarized rectenna with out-of-band suppression is proposed in this paper. The circular polarization is realized by corner perturbation on a rectangular radiation patch and enhanced by a diagonal slim slot etched at the center of the patch. An open stub connecting to the quarter wavelength impedance transformer is used to suppress out-of-band wave through harmonics notching. The results of simulations and experiments agree very well, which show that the rectenna obtained −19 dB return loss at 2.4 GHz and −15.5 dB, −18.1 dB, and −11.4 dB suppression on second, third, and fourth harmonic frequency bands, respectively. The reflection coefficient in overall out-of-band, up to 10 GHz, is limited up to −3 dB. Integrated with a voltage doubling rectification circuit, the proposed rectenna can obtain 75.5% RF-to-DC conversion efficiency.

Computational efficiency improvement with Wigner rotation technique in studying atoms in intense few-cycle circularly polarized pulses

International Nuclear Information System (INIS)

Yuan, Minghu; Feng, Liqiang; Lü, Rui; Chu, Tianshu

2014-01-01

We show that by introducing Wigner rotation technique into the solution of time-dependent Schrödinger equation in length gauge, computational efficiency can be greatly improved in describing atoms in intense few-cycle circularly polarized laser pulses. The methodology with Wigner rotation technique underlying our openMP parallel computational code for circularly polarized laser pulses is described. Results of test calculations to investigate the scaling property of the computational code with the number of the electronic angular basis function l as well as the strong field phenomena are presented and discussed for the hydrogen atom

Investigation of beam self-polarization in the future e+e- circular collider

Science.gov (United States)

Gianfelice-Wendt, E.

2016-10-01

The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the e+e- Future Circular Collider (FCC-e+e-) for Z and W W physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of self-polarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs) errors for a simplified FCC-e+e- ring are presented.

Dual-scale nanoripple/nanoparticle-covered microspikes on silicon by femtosecond double pulse train irradiation in water

Energy Technology Data Exchange (ETDEWEB)

Meng, Ge; Jiang, Lan [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Li, Xin, E-mail: lixin02@bit.edu.cn [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Xu, Yongda; Shi, Xuesong; Yan, Ruyu [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Lu, Yongfeng [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0511 (United States)

2017-07-15

Highlights: • A simple method to fabricate dual-scale structures on silicon is proposed. • Nanoripple-covered or nanoparticle-covered microspikes are obtained on Si firstly. • They are obtained by temporally-shaped fs laser one-step irradiation in water. • Their application in SERS was proved with a high sensitivity of up to 10{sup 8}. - Abstract: Novel dual-scale structures were obtained by femtosecond double pulse train (subpulse delay Δt > 0 ps) one-step irradiating silicon in water. The dual-scale structures consist of microspikes of ∼2 μm width and ∼0.5 μm height, and nanoripples with a mean period of 146 nm or nanoparticles with a mean diameter of 90 nm which entirely cover on the microspikes, for linearly polarized or circularly polarized femtosecond laser respectively. The formation of dual-scale structures involves the following processes: (1) Continuously laser energy deposited at femtosecond to picosecond timescales within silicon surfaces and central regions, will result in enhanced capillary waves and thinner melted silicon layers. Hence, the microspikes can be induced at laser fluences below ablation threshold; (2) Later (>500–800 pulses), a mass of debris and bubbles produced will lead to the remarkably and uniformly scattering or shielding of subsequent incident laser energy. Hence, the nanostructures can be induced. The novel structures exhibit high-sensitive surface enhanced Raman scattering with an enhancement factor of 10{sup 8} for Rhodamine 6G detecting. Besides, the novel structures have application potentials in improving the silicon hydrophobicity, antireflection, etc.

Polarization controlled deep sub-wavelength periodic features written by femtosecond laser on nanodiamond thin film surface

Energy Technology Data Exchange (ETDEWEB)

Kumar Kuntumalla, Mohan; Srikanth, Vadali V. S. S., E-mail: vvsssse@uohyd.ernet.in [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Rajamudili, Kuladeep; Rao Desai, Narayana [School of Physics, University of Hyderabad, Hyderabad 500046 (India)

2014-04-21

Deep sub-wavelength (Λ/λ = ∼0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration = ∼110 fs and central wavelength of ∼800 nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of < λ/4) of the surface features is less than the laser wavelength. This work gives an experimental proof of polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.

Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

Science.gov (United States)

Wang, Jigang

2014-03-01

Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

Competition of circularly polarized laser modes in the modulation instability of hot magnetoplasma

International Nuclear Information System (INIS)

Sepehri Javan, N.

2013-01-01

The present study is aimed to investigate the problem of modulation instability of an intense laser beam in the hot magnetized plasma. The propagation of intense circularly polarized laser beam along the external magnetic field is considered using a relativistic fluid model. The nonlinear equation describing the interaction of laser pulse with magnetized hot plasma is derived in the quasi-neutral approximation, which is valid for hot plasma. Nonlinear dispersion equation for hot plasma is obtained. For left- and right-hand polarizations, the growth rate of instability is achieved and the effect of temperature, external magnetic field, and kind of polarization on the growth rate is considered. It is observed that for the right-hand polarization, increase of magnetic field leads to the increasing of growth rate. Also for the left-hand polarization, increase of magnetic field inversely causes decrease of the growth rate.

Negative circular polarization dynamics in InP/InGaP quantum dots

Science.gov (United States)

Nekrasov, S. V.; Kusrayev, Yu G.; Akimov, I. A.; Korenev, V. L.; Langer, L.; Salewski, M.

2016-08-01

Photoluminescence (PL) negative circular polarization (NCP) dynamics of InP/InGaP quantum dots (QDs) was studied. Time resolved measurements of PL demonstrated that NCP vanishes, when transverse magnetic field is applied, while oscillations of polarization (that are typical for both low-dimensional and bulk materials) do not occur. Hole g-factor spread in the QD ensemble was supposed to be the most probable reason for such NCP magnetic field behavior. The dependence of NCP dynamics on the repetition period of excitation laser pulses was investigated. In case of fairly small repetition period (T = 13.3 ns) long living NCP (13.3 ns < t < 133 ns) was detected, what was ascribed to resident electron spin orientation, accumulated during many laser pulses. In that regime more than one luminescence polarization decay time exist.

Negative circular polarization dynamics in InP/InGaP quantum dots

International Nuclear Information System (INIS)

Nekrasov, S V; Kusrayev, Yu G; Akimov, I A; Korenev, V L; Langer, L; Salewski, M

2016-01-01

Photoluminescence (PL) negative circular polarization (NCP) dynamics of InP/InGaP quantum dots (QDs) was studied. Time resolved measurements of PL demonstrated that NCP vanishes, when transverse magnetic field is applied, while oscillations of polarization (that are typical for both low-dimensional and bulk materials) do not occur. Hole g-factor spread in the QD ensemble was supposed to be the most probable reason for such NCP magnetic field behavior. The dependence of NCP dynamics on the repetition period of excitation laser pulses was investigated. In case of fairly small repetition period (T = 13.3 ns) long living NCP (13.3 ns < t < 133 ns) was detected, what was ascribed to resident electron spin orientation, accumulated during many laser pulses. In that regime more than one luminescence polarization decay time exist. (paper)

Light trapping and circularly polarization at a Dirac point in 2D plasma photonic crystals

Science.gov (United States)

Li, Qian; Hu, Lei; Mao, Qiuping; Jiang, Haiming; Hu, Zhijia; Xie, Kang; Wei, Zhang

2018-03-01

Light trapping at the Dirac point in 2D plasma photonic crystal has been obtained. The new localized mode, Dirac mode, is attributable to neither photonic bandgap nor total internal reflection. It exhibits a unique algebraic profile and possesses a high-Q factor resonator of about 105. The Dirac point could be modulated by tuning the filling factor, plasma frequency and plasma cyclotron frequency, respectively. When a magnetic field parallel to the wave vector is applied, Dirac modes for right circularly polarized and left circularly polarized waves could be obtained at different frequencies, and the Q factor could be tuned. This property will add more controllability and flexibility to the design and modulation of novel photonic devices. It is also valuable for the possibilities of Dirac modes in photonic crystal containing other kinds of metamaterials.

Investigation of beam self-polarization in the future e^{+}e^{-} circular collider

Directory of Open Access Journals (Sweden)

E. Gianfelice-Wendt

2016-10-01

Full Text Available The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV in the e^{+}e^{-} Future Circular Collider (FCC-e^{+}e^{-} for Z and WW physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of self-polarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs errors for a simplified FCC-e^{+}e^{-} ring are presented.

Controlled assembly of high-order nanoarray metal structures on bulk copper surface by femtosecond laser pulses

Science.gov (United States)

Qin, Wanwan; Yang, Jianjun

2017-07-01

We report a new one-step maskless method to fabricate high-order nanoarray metal structures comprising periodic grooves and particle chains on a single-crystal Cu surface using femtosecond laser pulses at the central wavelength of 400 nm. Remarkably, when a circularly polarized infrared femtosecond laser pulse (spectrally centered at 800 nm) pre-irradiates the sample surface, the geometric dimensions of the composite structure can be well controlled. With increasing the energy fluence of the infrared laser pulse, both the groove width and particle diameter are observed to reduce, while the measured spacing-to-diameter ratio of the nanoparticles tends to present an increasing tendency. A physical scenario is proposed to elucidate the underlying mechanisms: as the infrared femtosecond laser pulse pre-irradiates the target, the copper surface is triggered to display anomalous transient physical properties, on which the subsequently incident Gaussian blue laser pulse is spatially modulated into fringe-like energy depositions via the excitation of ultrafast surface plasmon. During the following relaxation processes, the periodically heated thin-layer regions can be transferred into the metastable liquid rivulets and then they break up into nanodroplet arrays owing to the modified Rayleigh-like instability. This investigation indicates a simple integrated approach for active designing and large-scale assembly of complexed functional nanostructures on bulk materials.

Time-resolved Femtosecond Photon Echo Probes Bimodal Solvent Dynamics

NARCIS (Netherlands)

Pshenichnikov, M.S; Duppen, K.; Wiersma, D. A.

1995-01-01

We report on time-resolved femtosecond photon echo experiments of a dye molecule in a polar solution. The photon echo is time resolved by mixing the echo with a femtosecond gate pulse in a nonlinear crystal. It is shown that the temporal profile of the photon echo allows separation of the

In-line phase retarder and polarimeter for conversion of linear to circular polarization

Energy Technology Data Exchange (ETDEWEB)

Kortright, J.B.; Smith, N.V.; Denlinger, J.D. [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

An in-line polarimeter including phase retarder and linear polarizer was designed and commissioned on undulator beamline 7.0 for the purpose of converting linear to circular polarization for experiments downstream. In commissioning studies, Mo/Si multilayers at 95 eV were used both as the upstream, freestanding phase retarder and the downstream linear polarized. The polarization properties of the phase retarder were characterized by direct polarimetry and by collecting MCD spectra in photoemission from Gd and other magnetic surfaces. The resonant birefringence of transmission multilayers results from differing distributions of s- and p-component wave fields in the multilayer when operating near a structural (Bragg) interference condition. The resulting phase retardation is especially strong when the interference is at or near the Brewster angle, which is roughly 45{degrees} in the EUV and soft x-ray ranges.

Scanning differential polarization microscope: Its use to image linear and circular differential scattering

International Nuclear Information System (INIS)

Mickols, W.; Maestre, M.F.

1988-01-01

A differential polarization microscope that couples the sensitivity of single-beam measurement of circular dichroism and circular differential scattering with the simultaneous measurement of linear dichroism and linear differential scattering has been developed. The microscope uses a scanning microscope stage and single-point illumination to give the very shallow depth of field found in confocal microscopy. This microscope can operate in the confocal mode as well as in the near confocal condition that can allow one to program the coherence and spatial resolution of the microscope. This microscope has been used to study the change in the structure of chromatin during the development of sperm in Drosophila

Detecting primordial gravitational waves with circular polarization of the redshifted 21 cm line. II. Forecasts

Science.gov (United States)

Mishra, Abhilash; Hirata, Christopher M.

2018-05-01

In the first paper of this series, we showed that the CMB quadrupole at high redshifts results in a small circular polarization of the emitted 21 cm radiation. In this paper we forecast the sensitivity of future radio experiments to measure the CMB quadrupole during the era of first cosmic light (z ˜20 ). The tomographic measurement of 21 cm circular polarization allows us to construct a 3D remote quadrupole field. Measuring the B -mode component of this remote quadrupole field can be used to put bounds on the tensor-to-scalar ratio r . We make Fisher forecasts for a future Fast Fourier Transform Telescope (FFTT), consisting of an array of dipole antennas in a compact grid configuration, as a function of array size and observation time. We find that a FFTT with a side length of 100 km can achieve σ (r )˜4 ×10-3 after ten years of observation and with a sky coverage fsky˜0.7 . The forecasts are dependent on the evolution of the Lyman-α flux in the pre-reionization era, that remains observationally unconstrained. Finally, we calculate the typical order of magnitudes for circular polarization foregrounds and comment on their mitigation strategies. We conclude that detection of primordial gravitational waves with 21 cm observations is in principle possible, so long as the primordial magnetic field amplitude is small, but would require a very futuristic experiment with corresponding advances in calibration and foreground suppression techniques.

Extension of supercontinuum spectrum, generated in polarization-maintaining photonic crystal fiber, using chirped femtosecond pulses

Science.gov (United States)

Vengelis, Julius; Jarutis, Vygandas; Sirutkaitis, Valdas

2018-01-01

We present results of experimental and numerical investigation of supercontinuum (SC) generation in polarization-maintaining photonic crystal fiber (PCF) using chirped femtosecond pulses. The initial unchirped pump pulse source was a mode-locked Yb:KGW laser generating 52-nJ energy, 110-fs duration pulses at 1030 nm with a 76-MHz repetition rate. The nonlinear medium was a 32-cm-long polarization-maintaining PCF manufactured by NKT Photonics A/S. We demonstrated the influence of pump pulse chirp on spectral characteristics of a SC. We showed that by chirping pump pulses positively or negatively one can obtain a broader SC spectrum than in the case of unchirped pump pulses at the same peak power. Moreover, the extension can be controlled by changing the amount of pump pulse chirp. Numerical simulation results also indicated that pump pulse chirp yields an extension of SC spectrum.

A Wideband and Compact Circularly-Polarized Rectenna for Low Power Application

OpenAIRE

Okba , Abderrahim; Takacs , Alexandru; Aubert , Hervé; Bellion , Anthony; Grenana , D

2017-01-01

International audience; This paper presents a wideband and compact circularly polarized rectenna composed by an Archimedean spiral antenna that covers the S and C frequency bands and a silicon Schottky diode. This rectenna (rectifier + antenna) is used for electromagnetic energy harvesting over a wide frequency band, in order to power autonomous wireless sensors used for satellite health monitoring. For low incident power densities (around 14 µW/cm²) the measured efficiency of at least 19% be...

Chaotic scattering from hydrogen atoms in a circularly polarized laser field

International Nuclear Information System (INIS)

Okon, Elias; Parker, William; Chism, Will; Reichl, Linda E.

2002-01-01

We investigate the classical dynamics of a hydrogen atom in a circularly polarized laser beam with finite radius. The spatial cutoff for the laser field allows us to use scattering processes to examine the laser-atom dynamics. We find that for certain field parameters, the delay times, the angular momentum, and the distance of closest approach of the scattered electron exhibit fractal behavior. This fractal behavior is a signature of chaos in the dynamics of the atom-field system

Enantiopure distorted ribbon-shaped nanographene combining two-photon absorption-based upconversion and circularly polarized luminescence.

Science.gov (United States)

Cruz, Carlos M; Márquez, Irene R; Mariz, Inês F A; Blanco, Victor; Sánchez-Sánchez, Carlos; Sobrado, Jesús M; Martín-Gago, José A; Cuerva, Juan M; Maçôas, Ermelinda; Campaña, Araceli G

2018-04-28

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push-pull geometry and the extended network of sp 2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results.

Smart Sensing Methodology for Object Identification Using Circularly Polarized Luminescence from Coordination-Driven Self-Assembly.

Science.gov (United States)

Imai, Yuki; Nakano, Yuka; Kawai, Tsuyoshi; Yuasa, Junpei

2018-05-21

This work demonstrates a potential use of circularly polarized luminescence for object identification methodology in a sensor application. Towards this aim, we have developed new luminescence probes using pyrene derivatives as sensor luminophores. The probes [(R,R)- and (S,S)-Im2Py] contain two chiral imidazole moieties at 1,6-positions through ethynyl spacers (the angle between the spacers is close to 180°). The probe molecules spontaneously self-assemble into chiral stacks (P or M helicity) upon coordination to metal ions with tetrahedral coordination preference (e.g., Zn2+). The chiral probes display neither circular dichroism (CD) nor circularly polarized luminescence (CPL) in the absence of metal ions. However, [(R,R)- and (S,S)-Im2Py] begins to exhibit intense chiroptical activity (CD and CPL) upon self-assembly with Zn2+ ions. The unique chiroptical properties of [(R,R)- and (S,S)-Im2Py] with chemical stimuli-responsibility are capable of demonstrating the new sensing methodology using the CPL signal as detection output, enabling us to discriminate between a signal from the target analyte and that from non-target species. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Searching for Models Exhibiting High Circularly Polarized Luminescence: the Electroactive Inherently Chiral Oligothiophenes.

Science.gov (United States)

Benincori, Tiziana; Appoloni, Giulio; Mussini, Patrizia Romana; Arnaboldi, Serena; Cirilli, Roberto; Quartapelle Procopio, Elsa; Panigati, Monica; Abbate, Sergio; Mazzeo, Giuseppe; Longhi, Giovanna

2018-05-02

Two new inherently chiral oligothiophenes characterized by the atropisomeric 3,3'-bithianaphtene scaffold functionalized with fused ring bithiophene derivatives, namely 4H-cyclopenta [2,1-b3:4b']dithiophene (CPDT) and dithieno[3,3-b:2',3'-d]pyrrole (DTP), were synthesized. The racemates were fully characterized and resolved into antipodes by enantioselective HPLC. The enantiomers were analyzed through different chiroptical techniques: electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) were employed to attribute the absolute configuration (AC). Comparison of experimental and calculated VCD spectra confirmed the DFT calculated conformational characteristics. The compound functionalized with two CPDT units was oxidized with FeCl3 and ECD and CPL of the resulting material were measured. Circularly Polarized Luminescence (CPL) was measured in order to verify if inherently chiral oligothiophenes could be promising systems for chiral photonics applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Circularly polarized zero-phonon transitions of vacancies in diamond at high magnetic fields

Science.gov (United States)

Braukmann, D.; Glaser, E. R.; Kennedy, T. A.; Bayer, M.; Debus, J.

2018-05-01

We study the circularly polarized photoluminescence of negatively charged (NV-) and neutral (NV0) nitrogen-vacancy ensembles and neutral vacancies (V0) in diamond crystals exposed to magnetic fields of up to 10 T. We determine the orbital and spin Zeeman splitting as well as the energetic ordering of their ground and first-excited states. The spin-triplet and -singlet states of the NV- are described by an orbital Zeeman splitting of about 9 μ eV /T , which corresponds to a positive orbital g -factor of gL=0.164 under application of the magnetic field along the (001) and (111) crystallographic directions, respectively. The zero-phonon line (ZPL) of the NV- singlet is defined as a transition from the 1E' states, which are split by gLμBB , to the 1A1 state. The energies of the zero-phonon triplet transitions show a quadratic dependence on intermediate magnetic field strengths, which we attribute to a mixing of excited states with nonzero orbital angular momentum. Moreover, we identify slightly different spin Zeeman splittings in the ground (gs) and excited (es) triplet states, which can be expressed by a deviation between their spin g -factors: gS ,es=gS ,gs+Δ g with values of Δ g =0.014 and 0.029 in the (001) and (111) geometries, respectively. The degree of circular polarization of the NV- ZPLs depends significantly on the temperature, which is explained by an efficient spin-orbit coupling of the excited states mediated through acoustic phonons. We further demonstrate that the sign of the circular polarization degree is switched under rotation of the diamond crystal. A weak Zeeman splitting similar to Δ g μBB measured for the NV- ZPLs is also obtained for the NV0 zero-phonon lines, from which we conclude that the ground state is composed of two optically active states with compensated orbital contributions and opposite spin-1/2 momentum projections. The zero-phonon lines of the V0 show Zeeman splittings and degrees of the circular polarization with opposite

Calcium hydroxylapatite treatment of human skin: evidence of collagen turnover through picrosirius red staining and circularly polarized microscopy

Directory of Open Access Journals (Sweden)

Zerbinati N

2018-01-01

Full Text Available Nicola Zerbinati,1 Alberto Calligaro2 1Department of Surgical and Morphological Sciences, University of Insubria (Varese and Polyspecialist Medical Center, Pavia, 2Department of Public Health, Experimental and Forensic Medicine, Unit of Histology and Embryology, University of Pavia, Pavia, Italy Background: Calcium hydroxylapatite (CaHA, Radiesse® is a biocompatible, injectable filler for facial soft-tissue augmentation that provides volume to tissues, followed by a process of neocollagenesis for improved skin quality. Objective: To examine the effects of CaHA treatment on the molecular organization of collagen using a combination of picrosirius red staining and circularly polarized light microscopy.Methods: Five subjects received subdermal injection of 0.3 mL of CaHA in tissues scheduled for removal during abdominoplasty 2 months later. Tissue specimens from the CaHA injection site and a control untreated area were obtained from excised skin at the time of surgery. Processed tissue sections were stained with picrosirius red solution 0.1% and visualized under circularly polarized light microscopy for identification of thick mature (type I and thin newly formed (type III collagen fibers. Pixel signals from both the control and CaHA-treated areas were extracted from the images, and morphometric computerized hue analysis was performed to provide a quantitative evaluation of mature and newly formed collagen fibers.Results: Under picrosirius red staining and circularly polarized light microscopy, green/yellow areas (thin newly formed collagen type III were visible among the collagen fibers in tissue sections from the area of CaHA injection. In contrast, the majority of the collagen fibers appeared red (thick mature collagen type I in control tissues. Morphometric analysis confirmed that, following CaHA treatment, the proportion of fibers represented by thin newly formed collagen type III increased significantly (p<0.01 in comparison with the

Circular polarization control for the LCLS baseline in the soft X-ray regime

Energy Technology Data Exchange (ETDEWEB)

Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2010-12-15

The LCLS baseline includes a planar undulator system, which produces intense linearly polarized light in the wavelength range 0.15-1.5 nm. In the soft X-ray wavelength region polarization control from linear to circular is highly desirable for studying ultrafast magnetic phenomena and material science issues. Several schemes using helical undulators have been discussed in the context of the LCLS. One consists in replacing three of the last planar undulator segments by helical (APPLE III) ones. A second proposal, the 2nd harmonic helical afterburner, is based on the use of short, crossed undulators tuned to the second harmonic. This last scheme is expected to be the better one. Its advantages are a high (over 90%) and stable degree of circular polarization and a low cost. Its disadvantage is a small output power (1% of the power at the fundamental harmonic) and a narrow wavelength range. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. In the option presented here, the microbunching of the planar undulator is used too. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently passes through a short helical (APPLE II) radiator. In this case the microbunch structure is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be easily suppressed by letting radiation and electron beamthrough horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Using thin Beryllium foils for the slits the divergence of the electron beam halo will increase by Coulomb scattering, but the beam will propagate through the setup without electron losses. The applicability of our method is not

On the stability of a finite amplitude circularly polarized electromagnetic wave in an anisotropic plasma

International Nuclear Information System (INIS)

Brodin, G.; Lundberg, J.

1990-01-01

To study the stability of a finite amplitude circularly polarized electromagnetic wave in a plasma with pressure anisotropy we make use of a generalized version of the Chew-Goldberger-Low equations. The dispersion relation is derived. Special attention is focused on the MHD-limit. (orig.)

Generation of polarization-entangled photon pairs in a cascade of two type-I crystals pumped by femtosecond pulses

International Nuclear Information System (INIS)

Nambu, Yoshihiro; Usami, Koji; Tsuda, Yoshiyuki; Matsumoto, Keiji; Nakamura, Kazuo

2002-01-01

We report the generation of polarization-entangled photons by femtosecond-pulse-pumped spontaneous parametric down-conversion in a cascade of two type-I crystals. Highly entangled pulsed states were obtained by introducing a temporal delay between the two orthogonal polarization components of the pump field. They exhibited high-visibility quantum interference and a large concurrence value, without the need of postselection using narrow-bandwidth spectral filters. The results are well explained by the theory which incorporates the space-time dependence of interfering two-photon amplitudes if dispersion and birefringence in the crystals are appropriately taken into account. Such a pulsed entangled photon well localized in time domain is useful for various quantum communication experiments, such as quantum cryptography and quantum teleportation

Collisional redistribution of circularly polarized light in barium perturbed by argon

International Nuclear Information System (INIS)

Alford, W.J.; Andersen, N.; Belsley, M.; Cooper, J.; Warrington, D.M.; Burnett, K.

1984-01-01

We have measured the orientation of the Ba 6p 1 P level produced by collision-induced excitation from the ground state by circularly polarized light. The detuning dependence of the far-wing excited state orientation can be interpreted in terms of reorientation of molecular orbitals which occur during the collision. Effects due to rotational coupling are seen to occure at large blue wing detunings. We have also determined the collisional rate for destruction of orientation by measuring the pressure dependence of the excited state orientation. (orig.)

Fast helicity switching of x-ray circular polarization at beamline P09 at PETRA III

Energy Technology Data Exchange (ETDEWEB)

Strempfer, J., E-mail: Joerg.Strempfer@desy.de; Mardegan, J. R. L.; Francoual, S.; Veiga, L. S. I.; Spitzbart, T.; Zink, H. [Deutsches Elektronen Synchrotron (DESY), Notkestrasse 85, 22603 Hamburg (Germany); Bouchenoire, L. [XMaS, ESRF, 6 rue Jules Horowitz, BP220, Grenoble 38043 (France); Department of Physics, University of Liverpool, Liverpool, L69 7ZE (United Kingdom)

2016-07-27

At the resonant scattering and diffraction beamline P09 at PETRA III/DESY, polarization manipulation in the X-ray energy range 3-13 keV is possible using wave-plates. Recently, fast flipping of circular polarization helicity using the Raspberry Pi controlled FPGA (PiLC) device developed at DESY and dedicated piezo-electric flippers has been commissioned. Functionality of the PiLC for XMCD and first XMCD measurements at the Fe K-and Dy-L{sub 3} absorption edges are presented.

Study the effect of dye concentration on optical history using circular polarization holographic grating in thin polymeric film

International Nuclear Information System (INIS)

Mohajerani, E.; Hosain Nataj, N.

2006-01-01

By studying the effect of dye concentration, we obtained the optimal dye concentration for recording holographic gratings. The history of circular polarization grating is also investigated. We built polarization holographic grating with more than 2 weeks history. By using a mask in front of pump beam, different pictures could be built up in the film.

Obtaining high degree of circular polarization at X-ray FELs via a reverse undulator taper

Energy Technology Data Exchange (ETDEWEB)

Schneidmiller, E.A.; Yurkov, M.V.

2013-08-15

Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. The proposed method is rather universal, i.e. it can be used at SASE FELs and seeded (self-seeded) FELs, with any wavelength of interest, in a wide range of electron beam parameters, and with any repetition rate. It can be used at different X-ray FEL facilities, in particular at LCLS after installation of the helical afterburner in the near future.

Circularly Polarized Low-Profile Antenna for Radiating Parallel to Ground Plane for RFID Reader Applications

Directory of Open Access Journals (Sweden)

Kittima Lertsakwimarn

2013-01-01

Full Text Available This paper presents a low-profile printed antenna with double U-shaped arms radiating circular polarization for the UHF RFID readers. The proposed antenna consists of double U-shaped strip structures and a capacitive feeding line to generate circular polarization. A part of the U-shaped arms is bent by 90° to direct the main beam parallel to the ground plane. From the results, -10 dB |S11| and 3 dB axial ratio of the antenna cover a typical UHF RFID band from 920 MHz to 925 MHz. The bidirectional beam is obtained with the maximum gain of 1.8 dBic in the parallel direction to the ground plane at the 925 MHz. The overall size of the proposed antenna including ground plane is 107 mm × 57 mm × 12.8 mm (0.33λ0 × 0.17λ0 × 0.04λ0.

Nanotrumpets and circularly polarized luminescent nanotwists hierarchically self-assembled from an achiral C3-symmetric ester.

Science.gov (United States)

Sang, Yutao; Duan, Pengfei; Liu, Minghua

2018-04-17

An achiral C3-symmetric molecule was found to self-assemble into various hierarchical nanostructures such as nanotwists, nanotrumpets and nanobelts, in which the twisted fibers showed supramolecular chirality as well as circularly polarized luminescence although the compound is achiral.

Dynamical polarizability of graphene irradiated by circularly polarized ac electric fields

DEFF Research Database (Denmark)

Busl, Maria; Platero, Gloria; Jauho, Antti-Pekka

2012-01-01

We examine the low-energy physics of graphene in the presence of a circularly polarized electric field in the terahertz regime. Specifically, we derive a general expression for the dynamical polarizability of graphene irradiated by an ac electric field. Several approximations are developed...... that allow one to develop a semianalytical theory for the weak-field regime. The ac field changes qualitatively the single- and many-electron excitations of graphene: Undoped samples may exhibit collective excitations (in contrast to the equilibrium situation), and the properties of the excitations in doped...

Light reflection by the cuticle of C. aurigans scarabs: a biological broadband reflector of left handed circularly polarized light

Science.gov (United States)

Libby, E.; Azofeifa, D. E.; Hernández-Jiménez, M.; Barboza-Aguilar, C.; Solís, A.; García-Aguilar, I.; Arce-Marenco, L.; Hernández, A.; Vargas, W. E.

2014-08-01

Measured reflection spectra from elytra of Chrysina aurigans scarabs are reported. They show a broad reflection band for wavelengths from 0.525 to 1.0 μm with a sequence of maxima and minima reflection values superimposed on a mean value of around 40% for the high reflection band. Different mechanisms contributing to the reflection spectra have been considered, with the dominant effect, reflection of left handed circularly polarized light, being produced by a laminated left handed twisted structure whose pitch changes with depth through the procuticle in a more complex way than that characterizing broad band circular polarizers based on cholesteric liquid crystals.

Light reflection by the cuticle of C. aurigans scarabs: a biological broadband reflector of left handed circularly polarized light

International Nuclear Information System (INIS)

Libby, E; Azofeifa, D E; Hernández-Jiménez, M; García-Aguilar, I; Arce-Marenco, L; Hernández, A; Vargas, W E; Barboza-Aguilar, C; Solís, A

2014-01-01

Measured reflection spectra from elytra of Chrysina aurigans scarabs are reported. They show a broad reflection band for wavelengths from 0.525 to 1.0 μm with a sequence of maxima and minima reflection values superimposed on a mean value of around 40% for the high reflection band. Different mechanisms contributing to the reflection spectra have been considered, with the dominant effect, reflection of left handed circularly polarized light, being produced by a laminated left handed twisted structure whose pitch changes with depth through the procuticle in a more complex way than that characterizing broad band circular polarizers based on cholesteric liquid crystals. (fast track communication)

Optical circular deflector with attosecond resolution for ultrashort electron beam

Directory of Open Access Journals (Sweden)

Zhen Zhang

2017-05-01

Full Text Available A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM_{01^{*}} in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.

Circularly Polarized Slotted Microstrip Patch Antenna with Finite Ground Plane

Directory of Open Access Journals (Sweden)

Sanyog Rawat

2012-12-01

Full Text Available In this paper a new geometry of circularly polarized patch antenna is proposed with improved bandwidth. The radiation performance of proposed patch antenna is investigated using IE3D simulation software and its performance is compared with that of conventional rectangular patch antenna. The simulated return loss, axial ratio and impedance with frequency for the proposed antenna are reported in this paper. It is shown that by selecting suitable ground-plane dimensions, air gap and location of the slots, the impedance bandwidth can be enhanced upto 10.15% as compared to conventional rectangular patch (4.24% with an axial ratio bandwidth of 4.05%.

Local Electronic and Magnetic Structure of Ni below and above TC: A Spin-Resolved Circularly Polarized Resonant Photoemission Study

NARCIS (Netherlands)

Sinkovic, B.; Tjeng, L.H.; Brookes, N.B.; Goedkoop, J.B.; Hesper, R.; Pellegrin, E.; Groot, F.M.F. de; Altieri, S.; Hulbert, S.L.; Shekel, E.; Sawatzky, G.A.

1997-01-01

We report the measurement of the local Ni 3d spin polarization, not only below but also above the Curie temperature (TC), using the newly developed spin-resolved circularly polarized 2p (L3) resonant photoemission technique. The experiment identifies the presence of 3d8 singlets at high energies

Design, Manufacturing, and Testing of a 20/30-GHz Dual-Band Circularly Polarized Reflectarray Antenna

DEFF Research Database (Denmark)

Smith, Thomas Gunst; Gothelf, Ulrich; Kim, Oleksiy S.

2013-01-01

This letter documents the design, manufacturing, and testing of a single-layer dual-band circularly polarized reflectarray antenna for 19.7–20.2 and 29.5–30.0 GHz. The reflectarray is designed using the concentric dual split-loop element and the variable rotation technique that enables full 360......$^{\\circ}$ phase adjustment simultaneously in two separate frequency bands. The elements have been optimized to suppress cross-polar reflection. Thereafter, the element data is included in a design tool that computes the reflectarray layout and the associated radiation patterns. The reflectarray...

77 GHz MEMS antennas on high-resistivity silicon for linear and circular polarization

KAUST Repository

Sallam, M. O.

2011-07-01

Two new MEMS antennas operating at 77 GHz are presented in this paper. The first antenna is linearly polarized. It possesses a vertical silicon wall that carries a dipole on top of it. The wall is located on top of silicon substrate covered with a ground plane. The other side of the substrate carries a microstrip feeding network in the form of U-turn that causes 180 phase shift. This phase-shifter feeds the arms of the dipole antenna via two vertical Through-Silicon Vias (TSVs) that go through the entire wafer. The second antenna is circularly polarized and formed using two linearly polarized antennas spatially rotated with respect to each other by 90 and excited with 90 phase shift. Both antennas are fabricated using novel process flow on a single high-resistivity silicon wafer via bulk micromachining. Only three processing steps are required to fabricate these antennas. The proposed antennas have appealing characteristics, such as high polarization purity, high gain, and high radiation efficiency. © 2011 IEEE.

Near-infrared Polarimetry of the Outflow Source AFGL 6366S: Detection of Circular Polarization

Science.gov (United States)

Kwon, Jungmi; Nakagawa, Takao; Tamura, Motohide; Hough, James H.; Kandori, Ryo; Choi, Minho; Kang, Miju; Cho, Jungyeon; Nakajima, Yasushi; Nagata, Tetsuya

2018-07-01

We have carried out near-infrared circular and linear imaging polarimetry of the AFGL 6366S region. There is one large infrared reflection nebula associated with the AFGL 6366S cluster and one small infrared reflection nebula associated with AFGL 6366S NE. Prominent and extended polarized nebulosities over the AFGL 6366S cluster field are found to be composed of several components and local nebula peaks, and those nebulosities are illuminated by at least three sources, which is roughly consistent with a previous study. However, the detailed linear polarization patterns and their degrees differ from the earlier study. The brightest regions of the nebulae are illuminated by the IRAS/WISE source. In addition, we report the first detection of circular polarization (CP) in the reflection nebula associated with AFGL 6366S. The CP is as large as approximately 4% in the K s band, and the maximum CP extent is approximately 0.45 pc, which is comparable to that for the largest CP regions known to date, such as Orion and Mon R2, although the CP degrees are much smaller. The CP pattern is mostly quadrupolar, and its morphology resembles the shape of the C18O dense core. Therefore, the CP region is probably illuminated by the IRAS/WISE source and its polarization is amplified by the dichroic absorption of the dense core associated with the cluster. This is the ninth source whose degrees of CPs are measured to be greater than 3%, suggesting that large and extended infrared CP regions are common among mid- to high-mass young stellar objects.

Circularly Polarized Transparent Microstrip Patch Reflectarray Integrated with Solar Cell for Satellite Applications

OpenAIRE

Zainud-Deen, S. H.; El-Shalaby, N. A.; Gaber, S. M.; Malhat, H. A.

2016-01-01

Circularly polarized (CP) transparent microstrip reflectarray antenna is integrated with solar cell for small satellite applications at 10 GHz. The reflectarray unit cell consists of a perfect electric conductor (PEC) square patch printed on an optically transparent substrate with the PEC ground plane. A comparison between using transparent conducting polymers and using the PEC in unit-cell construction has been introduced. The waveguide simulator is used to calculate the required compensatio...

Helicity-Selective Phase-Matching and Quasi-Phase matching of Circularly Polarized High-Order Harmonics: Towards Chiral Attosecond Pulses

Science.gov (United States)

2016-05-23

2 Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA 3Department of Physics and Optical Engineering, Ort Braude...polarized high harmonic generation, phase matching, ultrafast chiral physics, attosecond pulses (Some figures may appear in colour only in the online...temporal resolution and in spectral regions unavailable to circular polarization thus far. Acknowledgments This work was supported by the USA –Israel

The circular polarization of gamma rays from heavy-ion reactions high above the Coulomb barrier

International Nuclear Information System (INIS)

Lauterbach, C.; Boer, J. de; Duennweber, W.; Graw, G.; Hering, W.; Puchta, H.; Trautmann, W.

1978-01-01

We have measured the circular polarization P of the γ radiation emitted in coincidence with the projectile-like fragments from the 100 MeV 16 O+ 27 Al, 58 Ni reactions at the Munich MP tandem accelerator and the 284 (303) Mev 40 Ar+Ag and 539 MeV 86 Kr+Ag reactions at the GSI UNILAC. (orig.) [de

Circularly polarized microwaves for magnetic resonance study in the GHz range: Application to nitrogen-vacancy in diamonds

International Nuclear Information System (INIS)

Mrózek, M.; Rudnicki, D. S.; Gawlik, W.; Mlynarczyk, J.

2015-01-01

The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85%; it is possible to address the specific spin states of a diamond sample using a low power microwave generator. The circuit may be applied to a wide range of magnetic resonance experiments with a well-controlled polarization of microwaves

Circularly Polarized Planar Helix Phased Antenna Array for 5G Mobile Terminals

DEFF Research Database (Denmark)

Syrytsin, Igor A.; Zhang, Shuai; Pedersen, Gert F.

2017-01-01

In this paper, a planar helix mobile phased antenna array is proposed for 5th generation communication systems with operating frequency of 28GHz. The proposed array displays circular polarization in the endfire direction. Over 65 degrees of axial ratio beamwidth and 7GHz of axial ratio bandwidth...... has been achieved in the proposed design. The coverage performance of the proposed phased antenna array has also been studied by using the coverage efficiency metric. Coverage efficiency of 50 % at 5 dBi gain is achieved by the proposed phased mobile antenna array....

A circularly polarized optical dipole trap and other developments in laser trapping of atoms

Science.gov (United States)

Corwin, Kristan Lee

Several innovations in laser trapping and cooling of alkali atoms are described. These topics share a common motivation to develop techniques for efficiently manipulating cold atoms. Such advances facilitate sensitive precision measurements such as parity non- conservation and 8-decay asymmetry in large trapped samples, even when only small quantities of the desired species are available. First, a cold, bright beam of Rb atoms is extracted from a magneto-optical trap (MOT) using a very simple technique. This beam has a flux of 5 × 109 atoms/s and a velocity of 14 m/s, and up to 70% of the atoms in the MOT were transferred to the atomic beam. Next, a highly efficient MOT for radioactive atoms is described, in which more than 50% of 221Fr atoms contained in a vapor cell are loaded into a MOT. Measurements were also made of the 221Fr 7 2P1/2 and 7 2P3/2 energies and hyperfine constants. To perform these experiments, two schemes for stabilizing the frequency of the light from a diode laser were developed and are described in detail. Finally, a new type of trap is described and a powerful cooling technique is demonstrated. The circularly polarized optical dipole trap provides large samples of highly spin-polarized atoms, suitable for many applications. Physical processes that govern the transfer of large numbers of atoms into the trap are described, and spin-polarization is measured to be 98(1)%. In addition, the trap breaks the degeneracy of the atomic spin states much like a magnetic trap does. This allows for RF and microwave cooling via both forced evaporation and a Sisyphus mechanism. Preliminary application of these techniques to the atoms in the circularly polarized dipole trap has successfully decreased the temperature by a factor of 4 while simultaneously increasing phase space density.

Controlling periodic ripple microstructure formation on 4H-SiC crystal with three time-delayed femtosecond laser beams of different linear polarizations.

Science.gov (United States)

He, Wanlin; Yang, Jianjun; Guo, Chunlei

2017-03-06

The control of laser-induced periodic ripple microstructures on 4H-SiC crystal surface is studied using temporally delayed collinear three femtosecond laser pulse trains linearly polarized in different directions. The ripple orientation appears to develop independent of the individual laser polarizations and exhibits non-monotonical change with variable time delays, whose variation tendency is also affected by the polarization intersection angles. Remarkably, the ripple period is observed to transfer from high- to low-spatial-frequency regions, accompanied by distinctly improved morphological uniformity and clearness. The results are satisfactorily interpreted based on a physical model of the surface wave excitation on a transient index metasurface, which is confirmed by further experiments. Our investigations indicate that transient noneqilibrium dynamics of the material surface provides an effective way to manipulate the laser-induced microstructures.

Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

International Nuclear Information System (INIS)

Barth, Ingo; Smirnova, Olga

2014-01-01

We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analyzing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Barth and Smirnova (2013 Phys. Rev. A 88 013401). We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields. (paper)

CPW-Fed Wideband Circular Polarized Antenna for UHF RFID Applications

Directory of Open Access Journals (Sweden)

Sun-Woong Kim

2017-01-01

Full Text Available We propose a wide bandwidth antenna with a circular polarization for universal Ultra High Frequency (UHF radio-frequency identification (RFID reader applications. To achieve a wide 3 dB axial ratio (AR bandwidth, three T-shaped microstrip lines are inserted into the ground plane. The measured impedance bandwidth of the proposed antenna is 480 MHz and extends from 660 to 1080 MHz, and the 3 dB AR bandwidth is 350 MHz and extends from 800 to 1155 MHz. The radiation pattern is a bidirectional pattern with a maximum antenna gain of 3.67 dBi. The overall size of the proposed antenna is 114 × 114 × 0.8 mm3.

Circularly Polarized S Band Dual Frequency Square Patch Antenna Using Glass Microfiber Reinforced PTFE Composite

Directory of Open Access Journals (Sweden)

M. Samsuzzaman

2014-01-01

Full Text Available Circularly polarized (CP dual frequency cross-shaped slotted patch antenna on 1.575 mm thick glass microfiber reinforced polytetrafluoroethylene (PTFE composite material substrate is designed and fabricated for satellite applications. Asymmetric cross-shaped slots are embedded in the middle of the square patch for CP radiation and four hexagonal slots are etched on the four sides of the square patch for desired dual frequency. Different substrate materials have been analysed to achieve the desired operating band. The experimental results show that the impedance bandwidth is approximately 30 MHz (2.16 GHz to 2.19 GHz for lower band and 40 MHz (3.29 GHz to 3.33 GHz for higher band with an average peak gain of 6.59 dBiC and 5.52 dBiC, respectively. Several optimizations are performed to obtain the values of the antenna physical parameters. Moreover, the proposed antenna possesses compactness, light weight, simplicity, low cost, and circularly polarized. It is an attractive candidate for dual band satellite antennas where lower band can be used for uplink and upper band can be used for downlink.

Ultra-wideband high-efficiency reflective linear-to-circular polarization converter based on metasurface at terahertz frequencies.

Science.gov (United States)

Jiang, Yannan; Wang, Lei; Wang, Jiao; Akwuruoha, Charles Nwakanma; Cao, Weiping

2017-10-30

The polarization conversion of electromagnetic (EM) waves, especially linear-to-circular (LTC) polarization conversion, is of great significance in practical applications. In this study, we propose an ultra-wideband high-efficiency reflective LTC polarization converter based on a metasurface in the terahertz regime. It consists of periodic unit cells, each cell of which is formed by a double split resonant square ring, dielectric layer, and fully reflective gold mirror. In the frequency range of 0.60 - 1.41 THz, the magnitudes of the reflection coefficients reach approximately 0.7, and the phase difference between the two orthogonal electric field components of the reflected wave is close to 90° or -270°. The results indicate that the relative bandwidth reaches 80% and the efficiency is greater than 88%, thus, ultra-wideband high-efficiency LTC polarization conversion has been realized. Finally, the physical mechanism of the polarization conversion is revealed. This converter has potential applications in antenna design, EM measurement, and stealth technology.

Improvement of RF Wireless Power Transmission Using a Circularly Polarized Retrodirective Antenna Array with EBG Structures

Directory of Open Access Journals (Sweden)

Son Trinh-Van

2018-02-01

Full Text Available This paper presents the performance improvement of a circularly polarized (CP retrodirective array (RDA through the suppression of mutual coupling effects. The RDA is designed based on CP Koch-shaped patch antenna elements with an inter-element spacing as small as 0.4 λ for a compact size ( λ is the wavelength in free space at the designed frequency of 5.2 GHz. Electromagnetic band gap (EBG structures are applied to reduce the mutual coupling between the antenna elements, thus improving the circular polarization characteristic of the RDA. Two CP RDAs with EBGs, in the case 5 × 5 and 10 × 10 arrays, are used as wireless power transmitters to transmit a total power of 50 W. A receiver is located at a distance of 1 m away from the transmitter to harvest the transmitted power. At the broadside direction, the simulated results demonstrate that the received powers are improved by approximately 11.32% and 12.45% when using the 5 × 5 and 10 × 10 CP RDAs with the EBGs, respectively, as the transmitters.

Electromagnetic frozen waves with radial, azimuthal, linear, circular, and elliptical polarizations

Science.gov (United States)

Corato-Zanarella, Mateus; Zamboni-Rached, Michel

2016-11-01

Frozen waves (FWs) are a class of diffraction- and attenuation-resistant beams whose intensity pattern along the direction of propagation can be chosen arbitrarily, thus making them relevant for engineering the spatial configuration of optical fields. To date, analyses of such beams have been done essentially for the scalar case, with the vectorial nature of the electromagnetic fields often neglected. Although it is expected that the field components keep the fundamental properties of the scalar FWs, a deeper understanding of their electromagnetic counterparts is mandatory in order to exploit their different possible polarization states. The purpose of this paper is to study the properties of electromagnetic FWs with radial, azimuthal, linear, circular, and elliptical polarizations under paraxial and nonparaxial regimes in nonabsorbing media. An intensity pattern is chosen for a scalar FW, and the vectorial solutions are built after it via the use of Maxwell's equations. The results show that the field components and the longitudinal component of the time-averaged Poynting vector closely follow the pattern chosen even under highly nonparaxial conditions, showing the robustness of the FW structure to parameters variations.

Investigation of beam self-polarization in the future e+e− circular collider

CERN Document Server

AUTHOR|(CDS)2075800

2016-10-24

The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the eþe− Future Circular Collider (FCC-eþe−) for Z and WW physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of selfpolarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs) errors for a simplified FCC-eþe− ring are presented.

Polarization and fluence effects in femtosecond laser induced micro/nano structures on stainless steel with antireflection property

Science.gov (United States)

Yao, Caizhen; Ye, Yayun; Jia, Baoshen; Li, Yuan; Ding, Renjie; Jiang, Yong; Wang, Yuxin; Yuan, Xiaodong

2017-12-01

In this paper, micro/nano structures on stainless steel were prepared in single spot irradiation mode and scan mode by using femtosecond laser technique. The influence of polarization and fluence on the formation of micro/nano structures were explored. Surface morphology, microstructure, roughness and composition of prepared samples were characterized. The antireflection property and wettability of laser treated samples were also tested and compared with that of original stainless steel.Results showed that the laser-induced spot consists of two distinct regions due to the Gaussian beam profile: a core region of moth-eye-like structure and a peripheral region of nanoparticles-covered laser-induced periodic surface structure (NC-LIPSS). The proportion of the core region and dimension of micro/nano structure increase with increasing laser fluence. Polarization can be used to tune the direction of NC-LIPSS. Atomic ratios of Cr and Mn increase and atomic ratio of Ni decreases after laser irradiation. Oxygen is not detected on laser irradiated samples, indicating that oxidation reactions are not significant during the interaction process between femtosecond laser and 304 stainless steel. These are good for the application of stainless steel as its physical properties would not change or even enhanced. The overlaps between two laser scan lines significantly influence the surface roughness and should be controlled carefully during the preparation process. The laser irradiated surface has a better antireflection property in comparison with that of original stainless steel, which may due to the scattering and absorption of micro/nano structures. Contact angle of micro/nano structured stainless steel decreases with the increase of laser fluence. The hydrophilic property can be explained by Wenzel's model. The interference between the surface plasmon wave and the incident light wave leads to the formation of NC-LIPSS.

Circular polarimetry of the magnetic compact binary AM Herculis

Energy Technology Data Exchange (ETDEWEB)

Piirola, V; Vilhu, O; Tuominen, I

1982-01-01

Circular polarimetry in the red and simultaneous photometric observations in the UBVRI bands during the period June 1 to 3, 1981, of AM Herculis are discussed. Peak value of negative circular polarization (- 15 %) is stronger than observed in 1976 to 1979. Variations in the shape of the polarization and light curves occur from night to night. Positive crossover and reversal of the sign of the circular polarization are only marginal. Long term changes in polarization may be partly due to precession of the axis of rotation of the white dwarf about the binary axis. However, the duration of the phase interval where circular polarization remains close to zero changes on a time scale of days, casting doubt on precession models. The changing shape and position of the accretion columns with respect to the magnetic axis could explain short term variations. (ESA)

Proton triggered circularly polarized luminescence in orthogonal- and co-assemblies of chiral gelators with achiral perylene bisimide.

Science.gov (United States)

Han, Dongxue; Han, Jianlei; Huo, Shengwei; Qu, Zuoming; Jiao, Tifeng; Liu, Minghua; Duan, Pengfei

2018-05-29

The orthogonal- or co-assembly of achiral perylene bisimide (PBI) with chiral gelators can be regulated by solvents. While the coassembly leads to the formation of chiroptical nanofibers through chirality transfer, the orthogonal assemblies could not. Moreover, protonation on the coassembled nanofibers could light up the circularly polarized luminescence (CPL).

Innovative applications of femtosecond laser induced self-organized nanostructure

International Nuclear Information System (INIS)

Shimotsuma, Yasuhiko; Miura, Kiyotaka; Sakakura, Masaaki

2015-01-01

The nanostructure induced by the direct-writing of femtosecond-laser pulses can open a new opportunity to develop avant-garde devices such as a 5D optical storage, polarization imaging sensor, thermoelectric conversion elements. (author)

Femtosecond Time-resolved Optical Polarigraphy (FTOP)

International Nuclear Information System (INIS)

Aoshima, S.; Fujimoto, M.; Hosoda, M.; Tsuchiya, Y.

2000-01-01

A novel time-resolved imaging technique named FTOP (Femtosecond Time-resolved Optical Polarigraphy) for visualizing the ultrafast propagation dynamics of intense light pulses in a medium has been proposed and demonstrated. Femtosecond snapshot images can be created with a high spatial resolution by imaging only the polarization components of the probe pulse; these polarization components change due to the instantaneous birefringence induced by the pump pulse in the medium. Ultrafast temporal changes in the two-dimensional spatial distribution of the optical pulse intensity were clearly visualized in consecutive images by changing the delay between the pump and probe. We observe that several filaments appear and then come together before the vacuum focus due to nonlinear effects in air. We also prove that filamentation dynamics such as the formation position and the propagation behavior are complex and are strongly affected by the pump energy. The results collected clearly show that this method FTOP succeeds for the first time in directly visualizing the ultrafast dynamics of the self-modulated nonlinear propagation of light. (author)

Counterintuitive angular shifts in the photoelectron momentum distribution for atoms in strong few-cycle circularly polarized laser pulses

DEFF Research Database (Denmark)

Martiny, Christian; Abu-Samha, Mahmoud; Madsen, Lars Bojer

2009-01-01

We solve the three-dimensional time-dependent Schrödinger equation for a three-cycle circularly polarized laser pulse interacting with an atom. The photoelectron momentum distributions show counterintuitive shifts, similar to those observed in a recent experiment (Eckle et al 2008 Science 322 1525...

Low-Gain Circularly Polarized Antenna with Torus-Shaped Pattern

Science.gov (United States)

Amaro, Luis R.; Kruid, Ronald C.; Vacchione, Joseph D.; Prata, Aluizio

2012-01-01

The Juno mission to Jupiter requires an antenna with a torus-shaped antenna pattern with approximately 6 dBic gain and circular polarization over the Deep Space Network (DSN) 7-GHz transmit frequency and the 8-GHz receive frequency. Given the large distances that accumulate en-route to Jupiter and the limited power afforded by the solar-powered vehicle, this toroidal low-gain antenna requires as much gain as possible while maintaining a beam width that could facilitate a +/-10deg edge of coverage. The natural antenna that produces a toroidal antenna pattern is the dipole, but the limited approx. = 2.2 dB peak gain would be insufficient. Here a shaped variation of the standard bicone antenna is proposed that could achieve the required gains and bandwidths while maintaining a size that was not excessive. The final geometry that was settled on consisted of a corrugated, shaped bicone, which is fed by a WR112 waveguide-to-coaxial- waveguide transition. This toroidal low-gain antenna (TLGA) geometry produced the requisite gain, moderate sidelobes, and the torus-shaped antenna pattern while maintaining a very good match over the entire required frequency range. Its "horn" geometry is also low-loss and capable of handling higher powers with large margins against multipactor breakdown. The final requirement for the antenna was to link with the DSN with circular polarization. A four-layer meander-line array polarizer was implemented; an approach that was fairly well suited to the TLGA geometry. The principal development of this work was to adapt the standard linear bicone such that its aperture could be increased in order to increase the available gain of the antenna. As one increases the aperture of a standard bicone, the phase variation across the aperture begins to increase, so the larger the aperture becomes, the greater the phase variation. In order to maximize the gain from any aperture antenna, the phase should be kept as uniform as possible. Thus, as the standard

Topological events on the lines of circular polarization in nonparaxial vector optical fields.

Science.gov (United States)

Freund, Isaac

2017-02-01

In nonparaxial vector optical fields, the following topological events are shown to occur in apparent violation of charge conservation: as one translates the observation plane along a line of circular polarization (a C line), the points on the line (C points) are seen to change not only the signs of their topological charges, but also their handedness, and, at turning points on the line, paired C points with the same topological charge and opposite handedness are seen to nucleate. These counter-intuitive events cannot occur in paraxial fields.

Femtosecond X-ray scattering in condensed matter

Energy Technology Data Exchange (ETDEWEB)

Korff Schmising, Clemens von

2008-11-24

This thesis investigates the manifold couplings between electronic and structural properties in crystalline Perovskite oxides and a polar molecular crystal. Ultrashort optical excitation changes the electronic structure and the dynamics of the connected reversible lattice rearrangement is imaged in real time by femtosecond X-ray scattering experiments. An epitaxially grown superlattice consisting of alternating nanolayers of metallic and ferromagnetic strontium ruthenate (SRO) and dielectric strontium titanate serves as a model system to study optically generated stress. In the ferromagnetic phase, phonon-mediated and magnetostrictive stress in SRO display similar sub-picosecond dynamics, similar strengths but opposite sign and different excitation spectra. The amplitude of the magnetic component follows the temperature dependent magnetization square, whereas the strength of phononic stress is determined by the amount of deposited energy only. The ultrafast, phonon-mediated stress in SRO compresses ferroelectric nanolayers of lead zirconate titanate in a further superlattice system. This change of tetragonal distortion of the ferroelectric layer reaches up to 2 percent within 1.5 picoseconds and couples to the ferroelectric soft mode, or ion displacement within the unit cell. As a result, the macroscopic polarization is reduced by up to 100 percent with a 500 femtosecond delay that is due to final elongation time of the two anharmonically coupled modes. Femtosecond photoexcitation of organic chromophores in a molecular, polar crystal induces strong changes of the electronic dipole moment via intramolecular charge transfer. Ultrafast changes of transmitted X-ray intensity evidence an angular rotation of molecules around excited dipoles following the 10 picosecond kinetics of the charge transfer reaction. Transient X-ray scattering is governed by solvation, masking changes of the chromophore's molecular structure. (orig.)

Femtosecond X-ray scattering in condensed matter

International Nuclear Information System (INIS)

Korff Schmising, Clemens von

2008-01-01

This thesis investigates the manifold couplings between electronic and structural properties in crystalline Perovskite oxides and a polar molecular crystal. Ultrashort optical excitation changes the electronic structure and the dynamics of the connected reversible lattice rearrangement is imaged in real time by femtosecond X-ray scattering experiments. An epitaxially grown superlattice consisting of alternating nanolayers of metallic and ferromagnetic strontium ruthenate (SRO) and dielectric strontium titanate serves as a model system to study optically generated stress. In the ferromagnetic phase, phonon-mediated and magnetostrictive stress in SRO display similar sub-picosecond dynamics, similar strengths but opposite sign and different excitation spectra. The amplitude of the magnetic component follows the temperature dependent magnetization square, whereas the strength of phononic stress is determined by the amount of deposited energy only. The ultrafast, phonon-mediated stress in SRO compresses ferroelectric nanolayers of lead zirconate titanate in a further superlattice system. This change of tetragonal distortion of the ferroelectric layer reaches up to 2 percent within 1.5 picoseconds and couples to the ferroelectric soft mode, or ion displacement within the unit cell. As a result, the macroscopic polarization is reduced by up to 100 percent with a 500 femtosecond delay that is due to final elongation time of the two anharmonically coupled modes. Femtosecond photoexcitation of organic chromophores in a molecular, polar crystal induces strong changes of the electronic dipole moment via intramolecular charge transfer. Ultrafast changes of transmitted X-ray intensity evidence an angular rotation of molecules around excited dipoles following the 10 picosecond kinetics of the charge transfer reaction. Transient X-ray scattering is governed by solvation, masking changes of the chromophore's molecular structure. (orig.)

Raman backscattering of circularly polarized electromagnetic waves propagating along a magnetic field

International Nuclear Information System (INIS)

Maraghechi, B.; Willett, J.e.

1979-01-01

The stimulated Raman backscattering of an intense electromagnetic wave propagating in the extraordinary mode along a uniform, static magnetic field is considered. The dispersion relation for a homogeneous magnetized plasma in the presence of the circularly polarized pump waves is developed in the cold-plasma approximation with the pump frequency above the plasma frequency. Formulas are derived for the threshold νsub(OT) of the parametric instability and for the growth rate γ of the backscattered extraordinary wave and Langmuir wave. The effects of the magnetic field parallel to the direction of propagation on νsub(0T) and γ are studied numerically. (author)

Optically Polarized Conduction-Band Electrons in Tungsten Observed by Spin-Polarized Photoemission

DEFF Research Database (Denmark)

Zürcher, P.; Meier, F.; Christensen, N. E.

1979-01-01

Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV......Along the (100) direction of tungsten, interband transitions induced by circularly polarized light of energy 1.5 eV...

Vitamin E Circular Dichroism Studies: Insights into Conformational Changes Induced by the Solvent’s Polarity

Directory of Open Access Journals (Sweden)

Drew Marquardt

2016-12-01

Full Text Available We used circular dichroism (CD to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index—a measure of the solvent’s ionizing ability, and a direct measurement of solvent–solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first step in examining the hydrogen bonding abilities of vitamin E in a lipid bilayer.

Simulation of circularly polarized luminescence spectra using coupled cluster theory

Energy Technology Data Exchange (ETDEWEB)

McAlexander, Harley R.; Crawford, T. Daniel, E-mail: crawdad@vt.edu [Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061 (United States)

2015-04-21

We report the first computations of circularly polarized luminescence (CPL) rotatory strengths at the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) level of theory. Using a test set of eight chiral ketones, we compare both dipole and rotatory strengths for absorption (electronic circular dichroism) and emission to the results from time-dependent density-functional theory (TD-DFT) and available experimental data for both valence and Rydberg transitions. For two of the compounds, we obtained optimized geometries of the lowest several excited states using both EOM-CCSD and TD-DFT and determined that structures and EOM-CCSD transition properties obtained with each structure were sufficiently similar that TD-DFT optimizations were acceptable for the remaining test cases. Agreement between EOM-CCSD and the Becke three-parameter exchange function and Lee-Yang-Parr correlation functional (B3LYP) corrected using the Coulomb attenuating method (CAM-B3LYP) is typically good for most of the transitions, though agreement with the uncorrected B3LYP functional is significantly worse for all reported properties. The choice of length vs. velocity representation of the electric dipole operator has little impact on the EOM-CCSD transition strengths for nearly all of the states we examined. For a pair of closely related β, γ-enones, (1R)-7-methylenebicyclo[2.2.1]heptan-2-one and (1S)-2-methylenebicyclo[2.2.1]heptan-7-one, we find that EOM-CCSD and CAM-B3LYP agree with the energetic ordering of the two possible excited-state conformations, resulting in good agreement with experimental rotatory strengths in both absorption and emission, whereas B3LYP yields a qualitatively incorrect result for the CPL signal of (1S)-2-methylenebicyclo[2.2.1]heptan-7-one. Finally, we predict that one of the compounds considered here, trans-bicyclo[3.3.0]octane-3,7-dione, is unique in that it exhibits an achiral ground state and a chiral first excited state, leading to a strong CPL

Anomalous Polarized Raman Scattering and Large Circular Intensity Differential in Layered Triclinic ReS2.

Science.gov (United States)

Zhang, Shishu; Mao, Nannan; Zhang, Na; Wu, Juanxia; Tong, Lianming; Zhang, Jin

2017-10-24

The Raman tensor of a crystal is the derivative of its polarizability tensor and is dependent on the symmetries of the crystal and the Raman-active vibrational mode. The intensity of a particular mode is determined by the Raman selection rule, which involves the Raman tensor and the polarization configurations. For anisotropic two-dimensional (2D) layered crystals, polarized Raman scattering has been used to reveal the crystalline orientations. However, due to its complicated Raman tensors and optical birefringence, the polarized Raman scattering of triclinic 2D crystals has not been well studied yet. Herein, we report the anomalous polarized Raman scattering of 2D layered triclinic rhenium disulfide (ReS 2 ) and show a large circular intensity differential (CID) of Raman scattering in ReS 2 of different thicknesses. The origin of CID and the anomalous behavior in polarized Raman scattering were attributed to the appearance of nonzero off-diagonal Raman tensor elements and the phase factor owing to optical birefringence. This can provide a method to identify the vertical orientation of triclinic layered materials. These findings may help to further understand the Raman scattering process in 2D materials of low symmetry and may indicate important applications in chiral recognition by using 2D materials.

All fiber optics circular-state swept source polarization-sensitive optical coherence tomography.

Science.gov (United States)

Lin, Hermann; Kao, Meng-Chun; Lai, Chih-Ming; Huang, Jyun-Cin; Kuo, Wen-Chuan

2014-02-01

A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ~12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe.

Polarization holograms in a bifunctional amorphous polymer exhibiting equal values of photoinduced linear and circular birefringences.

Science.gov (United States)

Provenzano, Clementina; Pagliusi, Pasquale; Cipparrone, Gabriella; Royes, Jorge; Piñol, Milagros; Oriol, Luis

2014-10-09

Light-controlled molecular alignment is a flexible and useful strategy introducing novelty in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics and addressing the development of smart optical devices. Azobenzene-containing polymers are well-known photocontrollable materials with large and reversible photoinduced optical anisotropies. The vectorial holography applied to these materials enables peculiar optical devices whose properties strongly depend on the relative values of the photoinduced birefringences. Here is reported a polarization holographic recording based on the interference of two waves with orthogonal linear polarization on a bifunctional amorphous polymer that, exceptionally, exhibits equal values of linear and circular birefringence. The peculiar photoresponse of the material coupled with the holographic technique demonstrates an optical device capable of decomposing the light into a set of orthogonally polarized linear components. The holographic structures are theoretically described by the Jones matrices method and experimentally investigated.

Field-induced spin splitting and anomalous photoluminescence circular polarization in C H3N H3Pb I3 films at high magnetic field

Science.gov (United States)

Zhang, Chuang; Sun, Dali; Yu, Zhi-Gang; Sheng, Chuan-Xiang; McGill, Stephen; Semenov, Dmitry; Vardeny, Zeev Valy

2018-04-01

The organic-inorganic hybrid perovskites show excellent optical and electrical properties for photovoltaic and a myriad of other optoelectronics applications. Using high-field magneto-optical measurements up to 17.5 T at cryogenic temperatures, we have studied the spin-dependent optical transitions in the prototype C H3N H3Pb I3 , which are manifested in the field-induced circularly polarized photoluminescence emission. The energy splitting between left and right circularly polarized emission bands is measured to be ˜1.5 meV at 17.5 T, from which we obtained an exciton effective g factor of ˜1.32. Also from the photoluminescence diamagnetic shift we estimate the exciton binding energy to be ˜17 meV at low temperature. Surprisingly, the corresponding field-induced circular polarization is "anomalous" in that the photoluminescence emission of the higher split energy band is stronger than that of the lower split band. This "reversed" intensity ratio originates from the combination of long electron spin relaxation time and hole negative g factor in C H3N H3Pb I3 , which are in agreement with a model based on the k.p effective-mass approximation.

Dual circularly polarized broadside beam antenna based on metasurfaces

Science.gov (United States)

Tellechea, A.; Caminita, F.; Martini, E.; Ederra, I.; Teniente, J.; Iriarte, J. C.; Gonzalo, R.; Maci, S.

2018-02-01

Design details of a Ku band metasurface (MTS) antenna with dual circularly polarized (CP) broadside radiation is shown in this work. By means of the surface impedance tensor modulation, synchronized propagation of two transversal magnetic (TM) and transverse electric (TE) surface waves (SWs) is ensured in the structure, which contribute to the radiation in broadside direction by the generation of a CP leaky wave. The structure is implemented by elliptical subwavelength metallic elements with a cross-shaped aperture in the center, printed on top of a thin substrate with high permittivity (AD1000 with a thickness of λ0/17). For the experimental validation, the MTS prototype has been excited employing an orthomode transducer composed by a metallic stepped septum inside an air-filled waveguide. Two orthogonal TE11 modes excited with ±90° phase shift in the feed couple with the TM and TE SWs supported by the MTS and generate RHCP or LHCP broadside beam. Experimental results are compared with the simulation predictions. Finally, conclusions are drawn.

Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate

International Nuclear Information System (INIS)

Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang

2016-01-01

Graphical abstract: - Highlights: • The NSRs and DSRs are obtained on silicon surface. • With increasing direct writing speed, the NSRs suddenly changes and becomes the DSRs. • We develop a Sipe–Drude interference theory by considering the thermal excitation. - Abstract: The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe–Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe–Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.

Mechanically Reconfigurable Single-Arm Spiral Antenna Array for Generation of Broadband Circularly Polarized Orbital Angular Momentum Vortex Waves.

Science.gov (United States)

Li, Long; Zhou, Xiaoxiao

2018-03-23

In this paper, a mechanically reconfigurable circular array with single-arm spiral antennas (SASAs) is designed, fabricated, and experimentally demonstrated to generate broadband circularly polarized orbital angular momentum (OAM) vortex waves in radio frequency domain. With the symmetrical and broadband properties of single-arm spiral antennas, the vortex waves with different OAM modes can be mechanically reconfigurable generated in a wide band from 3.4 GHz to 4.7 GHz. The prototype of the circular array is proposed, conducted, and fabricated to validate the theoretical analysis. The simulated and experimental results verify that different OAM modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The proposed method paves a reconfigurable way to generate multiple OAM vortex waves with spin angular momentum (SAM) in radio and microwave satellite communication applications.

Performances of a Compact, High-Power WB Source with Circular Polarization

Science.gov (United States)

Delmote, P.; Pinguet, S.; Bieth, F.

This paper presents the design and the performances of an embedded high-power microwave (HPM) wideband source, developed and built at the French-German Research Institute of Saint-Louis. The system was intended for dual use, homeland security, and military applications. It is powered by a 400 kV compact Marx generator with specificities in coaxial design and low energy. The slow monopolar signal from the Marx is sharpened using a pulse-forming stage, made of a switching module pressurized with nitrogen, followed by a monopulse-to-monocycle converter. The duration and rise times of this signal could be adjusted by varying the pressure and space between electrodes. Repetitive operations were performed up to 100 Hz during 10 s without a gas flow. Two kinds of antennas can be connected to the source. The first one is a TEM horn, with an optional dielectric lens, that radiates a vertically polarized UWB short pulse. The second one is a nine-turn helix, working in Kraus monopolar axial mode and radiating a circularly polarized wideband signal along the main axis. A dedicated conical reflector increases its directivity and bandwidth. The whole source is designed to be embedded inside an aluminum trailer, powered by batteries and remote controlled through an optical fiber.

Pyrene-Containing ortho-Oligo(phenylene)ethynylene Foldamer as a Ratiometric Probe Based on Circularly Polarized Luminescence.

Science.gov (United States)

Reiné, Pablo; Justicia, Jose; Morcillo, Sara P; Abbate, Sergio; Vaz, Belen; Ribagorda, María; Orte, Ángel; Álvarez de Cienfuegos, Luis; Longhi, Giovanna; Campaña, Araceli G; Miguel, Delia; Cuerva, Juan M

2018-04-20

In this manuscript, we report the first synthesis of an organic monomolecular emitter, which behaves as a circularly polarized luminescence (CPL)-based ratiometric probe. The enantiopure helical ortho-oligo(phenylene)ethynylene ( o-OPE) core has been prepared by a new and efficient macrocyclization reaction. The combination of such o-OPE helical skeleton and a pyrene couple leads to two different CPL emission features in a single structure whose ratio linearly responds to silver(I) concentration.

Femtosecond laser processing of photovoltaic and transparent materials

Science.gov (United States)

Ahn, Sanghoon

The photovoltaic semiconducting and transparent dielectric materials are of high interest in current industry. Femtosecond laser processing can be an effective technique to fabricate such materials since non-linear photochemical mechanisms predominantly occur. In this series of studies, femtosecond (fs) laser processing techniques that include laser drilling on Si wafer, laser scribing on CIGS thin film, laser ablation on Lithium Niobate (LN) crystal, and fabrication of 3D structures in fused silica were studied. The fs laser drilling on Si wafer was performed to fabricate via holes for wrap-through PV devices. For reduction of the number of shots in fs laser drilling process, self-action of laser light in the air was initiated. To understand physical phenomena during laser drilling, scanning electron microscopy (SEM), emission, and shadowgraph images were studied. The result indicated the presence of two mechanisms that include fabrication by self-guided beam and wall-guided beam. Based on our study, we could fabricate ~16 micrometer circular-shaped via holes with ~200 laser pulses on 160-170 micrometer thick c- and mc-Si wafer. For the fs laser scribing on ink jet printed CIGS thin film solar cell, the effect of various parameters that include pulse accumulation, wavelength, pulse energy, and overlapping were elucidated. In our processing regime, the effect of wavelength could be diminished due to compensation between beam size, pulse accumulation, energy fluence, and the absorption coefficient. On the other hand, for high PRF fs laser processing, pulse accumulation effect cannot be ignored, while it can be negligible in low PRF fs laser processing. The result indicated the presence of a critical energy fluence for initiating delamination of CIGS layer. To avoid delamination and fabricate fine isolation lines, the overlapping method can be applied. With this method, ~1 micrometer width isolation lines were fabricated. The fs laser ablation on LN wafer was studied

Unusual Circularly Polarized and Aggregation-Induced Near-Infrared Phosphorescence of Helical Platinum(II) Complexes with Tetradentate Salen Ligands.

Science.gov (United States)

Song, Jintong; Wang, Man; Zhou, Xiangge; Xiang, Haifeng

2018-05-17

A series of chiral and helical Pt II -Salen complexes with 1,1'-binaphthyl linkers were synthesized and characterized. Owing to the restriction of intramolecular motions of central 1,1'-binaphthyls, the complexes exhibit unusual near-infrared aggregation-induced phosphorescence (AIP). The (R)/(S) enantiopure complexes were characterized by X-ray diffraction, circular dichroism spectra, time-dependent density functional theory calculations, and circularly polarized luminescence (CPL). The present work explores the use of tetradentate ligands that can be easily prepared from commercially available enantiopure compounds, and the subsequent preparation of stable CPL-active square planar Pt II complexes with AIP effect that may have interest in many applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A spin-optoelectronic detector for the simultaneous measurement of the degree of circular polarization and intensity of a laser beam

International Nuclear Information System (INIS)

Khamari, Shailesh K.; Porwal, S.; Oak, S. M.; Sharma, T. K.

2015-01-01

Simultaneous measurement of the degree of circular polarization and intensity of a laser beam is essential in advanced photonic applications. However, it is not feasible with conventional helicity dependent detectors where an additional detector is needed to measure the intensity. Here, we report the development of a spin-optoelectronic detector that can measure the degree of circular polarization and the intensity of a laser beam simultaneously. The principle of operation of device is based on the two independent fundamental phenomena occurring in Au/InP hybrid structures, namely, Inverse Spin Hall Effect (ISHE) and the Photo-Voltaic (PV) Effect. The magnitude of ISHE and PV signals is simultaneously measured across the two pairs of contacts that are made on the top of device. No cross talk is observed between the two detectors made on the same chip. The all-electronic compact device is fast, operates at room temperature, and opens up the possibility of many applications in an integrated optoelectronic platform

Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

DEFF Research Database (Denmark)

Nikolova, L.; Todorov, T.; Ivanov, M.

1997-01-01

We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

Scattering of inhomogeneous circularly polarized optical field and mechanical manifestation of the internal energy flows

DEFF Research Database (Denmark)

Bekshaev, A. Ya; Angelsky, O. V.; Hanson, Steen Grüner

2012-01-01

between the forward- and backward-scattered momentum fluxes in the Rayleigh scattering regime appears due to the spin part of the internal energy flow in the incident beam. The transverse ponderomotive forces exerted on dielectric and conducting particles of different sizes are calculated and special......Based on the Mie theory and on the incident beam model via superposition of two plane waves, we analyze numerically the momentum flux of the field scattered by a spherical, nonmagnetic microparticle placed within the spatially inhomogeneous circularly polarized paraxial light beam. The asymmetry...

Efficient laser emission from cladding waveguide inscribed in Nd:GdVO(4) crystal by direct femtosecond laser writing.

Science.gov (United States)

Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

2014-08-01

We report on the fabrication of depressed cladding waveguides in Nd:GdVO(4) laser crystal by using femtosecond laser inscription. The cross section of the structure is a circular shape with a diameter of 150 μm. Under the optical pump at 808 nm, the continuous wave (cw) as well as pulsed (Q-switched by graphene saturable absorber) waveguide lasing at 1064 nm has been realized, supporting guidance of both TE and TM polarizations. The maximum output power of 0.57 W was obtained in the cw regime, while the maximum pulse energy of the pulsed laser emissions was up to 19 nJ (corresponding to a maximum average output power of 0.33 W, at a resonant frequency of 18 MHz). The slope efficiencies achieved for the cw and pulsed Nd:GdVO(4) waveguide lasers were as high as 68% and 52%, respectively.

Photoexcitation circular dichroism in chiral molecules

Science.gov (United States)

Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

2018-05-01

Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

Analysis of chirality by femtosecond laser ionization mass spectrometry.

Science.gov (United States)

Horsch, Philipp; Urbasch, Gunter; Weitzel, Karl-Michael

2012-09-01

Recent progress in the field of chirality analysis employing laser ionization mass spectrometry is reviewed. Emphasis is given to femtosecond (fs) laser ionization work from the author's group. We begin by reviewing fundamental aspects of determining circular dichroism (CD) in fs-laser ionization mass spectrometry (fs-LIMS) discussing an example from the literature (resonant fs-LIMS of 3-methylcyclopentanone). Second, we present new data indicating CD in non-resonant fs-LIMS of propylene oxide. Copyright © 2012 Wiley Periodicals, Inc., A Wiley Company.

CIRCULARLY POLARIZED SLOTTED APERTURE ANTENNA WITH COPLANAR WAVEGUIDE FED FOR BROADBAND APPLICATIONS

Directory of Open Access Journals (Sweden)

B. T. P. MADHAV

2016-02-01

Full Text Available Coplanar waveguide fed circularly polarized microstrip patch antenna performance evaluation is presented in this paper. The broadband characteristics are attained by placing open end slot at the lower side of the antenna. The proposed design has the return loss of less than -10dB and VSWR<2 in the desired band of operation. A gain of 3dB to 4dB is attained in the desired band with good radiation characteristics and a suitable axial ratio of less than 3 dB is attained in the prescribed band of operation. Proposed antenna is fabricated on the FR4 substrate with dielectric constant of 4.4. Parametric analysis with change in substrate permittivity also performed and the optimized dimensions are presented in this work.

Cup waveguide antenna with integrated polarizer and OMT

Science.gov (United States)

Acosta, Roberto J. (Inventor); Kory, Carol (Inventor); Lambert, Kevin M. (Inventor)

2011-01-01

A cup waveguide antenna with integrated polarizer and OMT for simultaneously communicating left and right hand circularly polarized electromagnetic waves is adjustable to obtain efficient propagation and reception of electromagnetic waves. The antenna includes a circular waveguide having an orthomode transducer utilizing first and second pins longitudinally spaced apart and oriented orthogonally with respect to each other. Six radially-oriented adjustable polarizer screws extend from the exterior to the interior of the waveguide. A septum intermediate the first and second pins is aligned with the first pin. Adjustment of the polarizer screws enables maximized propagation of and/or response to left hand circularly polarized electromagnetic waves by the first pin while simultaneously enabling maximized propagation of and/or response to right hand circularly polarized electromagnetic waves by the second pin.

Narrow titanium oxide nanowires induced by femtosecond laser pulses on a titanium surface

Energy Technology Data Exchange (ETDEWEB)

Li, Hui; Li, Xian-Feng [Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Zhang, Cheng-Yun [School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Tie, Shao-Long [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Lan, Sheng, E-mail: slan@scnu.edu.cn [Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China)

2017-02-28

Highlights: • Titanium oxide nanowires with a feature width as narrow as ∼20 nm were induced on a titanium surface by using femtosecond laser pulses at 400 nm. • An evolution of the surface structure from a high spatial frequency laser-induced periodic structure parallel to the laser polarization to a low spatial frequency one perpendicular to the laser polarization was observed with increasing irradiation pulse number. • The formation of the titanium oxide nanowires was confirmed by the energy dispersive spectroscopy measurements and the evolution of the surface structure was successfully interpreted by using the efficacy factor theory. - Abstract: The evolution of the nanostructure induced on a titanium (Ti) surface with increasing irradiation pulse number by using a 400-nm femtosecond laser was examined by using scanning electron microscopy. High spatial frequency periodic structures of TiO{sub 2} parallel to the laser polarization were initially observed because of the laser-induced oxidation of the Ti surface and the larger efficacy factor of TiO{sub 2} in this direction. Periodically aligned TiO{sub 2} nanowires with featured width as small as 20 nm were obtained. With increasing pulse number, however, low spatial frequency periodic structures of Ti perpendicular to the laser polarization became dominant because Ti possesses a larger efficacy factor in this direction. The competition between the high- and low-spatial frequency periodic structures is in good agreement with the prediction of the efficacy factor theory and it should also be observed in the femtosecond laser ablation of other metals which are easily oxidized in air.

Testing the magnetar scenario for superluminous supernovae with circular polarimetry

Science.gov (United States)

Cikota, Aleksandar; Leloudas, Giorgos; Bulla, Mattia; Inserra, Cosimo; Chen, Ting-Wan; Spyromilio, Jason; Patat, Ferdinando; Cano, Zach; Cikota, Stefan; Coughlin, Michael W.; Kankare, Erkki; Lowe, Thomas B.; Maund, Justyn R.; Rest, Armin; Smartt, Stephen J.; Smith, Ken W.; Wainscoat, Richard J.; Young, David R.

2018-05-01

Superluminous supernovae (SLSNe) are at least ˜5 times more luminous than common supernovae (SNe). Especially hydrogen-poor SLSN-I are difficult to explain with conventional powering mechanisms. One possible scenario that might explain such luminosities is that SLSNe-I are powered by an internal engine, such as a magnetar or an accreting black hole. Strong magnetic fields or collimated jets can circularly polarize light. In this work, we measured circular polarization of two SLSNe-I with the FOcal Reducer and low dispersion Spectrograph (FORS2) mounted at the ESO's Very Large Telescope (VLT). PS17bek, a fast evolving SLSN-I, was observed around peak, while OGLE16dmu, a slowly evolving SLSN-I, was observed 100 days after maximum. Neither SLSN shows evidence of circularly polarized light, however, these non-detections do not rule out the magnetar scenario as the powering engine for SLSNe-I. We calculate the strength of the magnetic field and the expected circular polarization as a function of distance from the magnetar, which decreases very fast. Additionally, we observed no significant linear polarization for PS17bek at four epochs, suggesting that the photosphere near peak is close to spherical symmetry.

Femtosecond laser ablation of transparent microphotonic devices and computer-generated holograms.

Science.gov (United States)

Alqurashi, Tawfiq; Montelongo, Yunuen; Penchev, Pavel; Yetisen, Ali K; Dimov, Stefan; Butt, Haider

2017-09-21

Femtosecond laser ablation allows direct patterning of engineering materials in industrial settings without requiring multistage processes such as photolithography or electron beam lithography. However, femtosecond lasers have not been widely used to construct volumetric microphotonic devices and holograms with high reliability and cost efficiency. Here, a direct femtosecond laser writing process is developed to rapidly produce transmission 1D/2D gratings, Fresnel Zone Plate lenses, and computer-generated holograms. The optical properties including light transmission, angle-dependent resolution, and light polarization effects for the microphotonic devices have been characterized. Varying the depth of the microgratings from 400 nm to 1.5 μm allowed the control over their transmission intensity profile. The optical properties of the 1D/2D gratings were validated through a geometrical theory of diffraction model involving 2D phase modulation. The produced Fresnel lenses had transmission efficiency of ∼60% at normal incidence and they preserved the polarization of incident light. The computer-generated holograms had an average transmission efficiency of 35% over the visible spectrum. These microphotonic devices had wettability resistance of contact angle ranging from 44° to 125°. These devices can be used in a variety of applications including wavelength-selective filters, dynamic displays, fiber optics, and biomedical devices.

Circular polarization control for the European XFEL in the soft X-ray regime

Energy Technology Data Exchange (ETDEWEB)

Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2011-06-15

The possibility of producing X-ray radiation with high degree of circular polarization is an important asset at XFEL facilities. Polarization control is most important in the soft X-ray region.However, the baseline of the European XFEL, including the soft X-ray SASE3 line, foresees planar undulators only, yielding linearly-polarized radiation. It is clear that the lowest-risk strategy for implementing polarization control at SASE3 involves adding an APPLE II-type undulator at the end of the planar undulator, in order to exploit the micro bunching from the baseline FEL. Detailed experience is available in synchrotron radiation laboratories concerning the manufacturing of 5 m-long APPLE II undulators. However, the choice of a short helical radiator leads to the problem of background suppression. The driving idea of our proposal is that the background radiation can be suppressed by spatial filtering. This operation can be performed by inserting slits behind the APPLE II radiator, where the linearly-polarized radiation spot size is about 30 times larger than the radiation spot size from the helical radiator. The last 7 cells of the SASE3 undulator are left with an open gap in order to provide a total 42 m drift section for electron beam and radiation. Due to the presence of the drift the linearly-polarized radiation spot size increases, and the linearly polarized background radiation can be suppressed by the slits. At the same time, the microbunch structure is easily preserved, so that intense (100 GW) coherent radiation is emitted in the helical radiator. We propose a filtering setup consisting of a pair of water cooled slits for X-ray beam filtering and of a 5 m-long magnetic chicane, which creates an offset for slit installation immediately behind the helical radiator. Electrons and X-rays are separated before the slits by the magnetic chicane, so that the electron beam can pass by the filtering setup without perturbations. Based on start-to-end simulations we

Circular polarization control for the European XFEL in the soft X-ray regime

International Nuclear Information System (INIS)

Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

2011-06-01

The possibility of producing X-ray radiation with high degree of circular polarization is an important asset at XFEL facilities. Polarization control is most important in the soft X-ray region.However, the baseline of the European XFEL, including the soft X-ray SASE3 line, foresees planar undulators only, yielding linearly-polarized radiation. It is clear that the lowest-risk strategy for implementing polarization control at SASE3 involves adding an APPLE II-type undulator at the end of the planar undulator, in order to exploit the micro bunching from the baseline FEL. Detailed experience is available in synchrotron radiation laboratories concerning the manufacturing of 5 m-long APPLE II undulators. However, the choice of a short helical radiator leads to the problem of background suppression. The driving idea of our proposal is that the background radiation can be suppressed by spatial filtering. This operation can be performed by inserting slits behind the APPLE II radiator, where the linearly-polarized radiation spot size is about 30 times larger than the radiation spot size from the helical radiator. The last 7 cells of the SASE3 undulator are left with an open gap in order to provide a total 42 m drift section for electron beam and radiation. Due to the presence of the drift the linearly-polarized radiation spot size increases, and the linearly polarized background radiation can be suppressed by the slits. At the same time, the microbunch structure is easily preserved, so that intense (100 GW) coherent radiation is emitted in the helical radiator. We propose a filtering setup consisting of a pair of water cooled slits for X-ray beam filtering and of a 5 m-long magnetic chicane, which creates an offset for slit installation immediately behind the helical radiator. Electrons and X-rays are separated before the slits by the magnetic chicane, so that the electron beam can pass by the filtering setup without perturbations. Based on start-to-end simulations we

Circularly Polarized Luminescence from Inorganic Materials: Encapsulating Guest Lanthanide Oxides in Chiral Silica Hosts.

Science.gov (United States)

Sugimoto, Masumi; Liu, Xin-Ling; Tsunega, Seiji; Nakajima, Erika; Abe, Shunsuke; Nakashima, Takuya; Kawai, Tsuyoshi; Jin, Ren-Hua

2018-05-02

Recently, circularly polarized luminescence (CPL)-active systems have become a very hot and interesting subject in chirality- and optics-related areas. The CPL-active systems are usually available by two approaches: covalently combining a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organic, although the luminescent components were alternatively organics or inorganics. Herein, the first totally inorganic CPL-active system by "luminescent guest-chiral host" strategy is proposed. Luminescent sub-10 nm lanthanide oxides (Eu 2 O 3 or Tb 2 O 3 ) nanoparticles (guests) were encapsulated into chiral non-helical SiO 2 nanofibres (host) through calcination of chiral SiO 2 hybrid nanofibres, trapping Eu 3+ (or Tb 3+ ). These lanthanide oxides display circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu 3+ and 545 nm for Tb 3+ . This work has implications for inorganic-based CPL-active systems by incorporation of various luminescent guests within chiral inorganic hosts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

DEFF Research Database (Denmark)

Hansen, Jonas Lerche; Holmegaard, Lotte; Kalhøj, Line

2011-01-01

are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position...... of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D...

Compact circularly polarized truncated square ring slot antenna with suppressed higher resonances.

Directory of Open Access Journals (Sweden)

Mursyidul Idzam Sabran

Full Text Available This paper presents a compact circularly polarized (CP antenna with an integrated higher order harmonic rejection filter. The proposed design operates within the ISM band of 2.32 GHz- 2.63 GHz and is suitable for example for wireless power transfer applications. Asymmetrical truncated edges on a square ring create a defected ground structure to excite the CP property, simultaneously realizing compactness. It offers a 50.5% reduced patch area compared to a conventional design. Novel stubs and slot shapes are integrated in the transmission line to reduce higher (up to the third order harmonics. The proposed prototype yields a -10 dB reflection coefficient (S11 impedance bandwidth of 12.53%, a 3 dB axial ratio bandwidth of 3.27%, and a gain of 5.64 dBi. Measurements also show good agreement with simulations.

On the anisotropy of stress-distribution induced in glasses and crystals by non-ablative femtosecond laser exposure

NARCIS (Netherlands)

McMillen, B.W.; Bellouard, Y.

2015-01-01

Femtosecond laser exposure in the non-ablative regime induces a variety of bulk structural modifications, in which anisotropy may depend on the polarization of the writing beam. In this work, we investigate the correlation between polarization state and stress anisotropy. In particular, we introduce

Polarization-dependent diffraction in all-dielectric, twisted-band structures

Energy Technology Data Exchange (ETDEWEB)

Kardaś, Tomasz M.; Jagodnicka, Anna; Wasylczyk, Piotr, E-mail: pwasylcz@fuw.edu.pl [Photonic Nanostructure Facility, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

2015-11-23

We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with different efficiencies. Non-birefringent structures as thin as 3 μm have a significant difference in diffraction efficiency for left- and right-hand circular polarizations. We identify the structural parameters of such twisted-band matrices for optimum performance as circular polarizers.

Spatiotemporal polarization gradients in phase-bearing light

International Nuclear Information System (INIS)

Lembessis, V. E.; Babiker, M.

2010-01-01

It is shown how the interference of two circularly polarized laser beams endowed with orbital angular momentum can give rise to spatial and temporal polarization gradients, displaying axial as well as angular symmetry properties. Illustrations are given with reference to circularly polarized Laguerre-Gaussian beams as typical light beams carrying orbital angular momentum.

Momentum distributions of selected rare-gas atoms probed by intense femtosecond laser pulses

DEFF Research Database (Denmark)

Abu-Samha, Mahmoud; Madsen, Lars Bojer

2011-01-01

We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses. The cal......We provide a direct comparison between numerical and experimental (Rudenko et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 L407) photoelectron momentum distributions in strong-field ionization of selected rare-gas atoms (He, Ne and Ar), probed by femtosecond linearly polarized laser pulses....... The calculations are performed by solving the time-dependent Schrödinger equation within the single-active-electron approximation, and focal-volume effects are taken into account by appropriately averaging the results. The resulting momentum distributions are in quantitative agreement with the experimental...

Optical force and torque on a dielectric Rayleigh particle by a circular Airy vortex beam

Science.gov (United States)

Chen, Musheng; Huang, Sujuan; Shao, Wei; Liu, Xianpeng

2018-03-01

Optical force and torque exerted on the Rayleigh particles by tightly focused circularly polarized circular Airy vortex beams (CAVB) in the far field are studied in this paper. The relation between parameters of circularly polarized CAVB and the trapping properties is numerically analyzed based on Rayleigh models and the Debye diffraction theory. The results show that both the high refractive index and low refractive index particles can be fully stably trapped in three dimensions by circularly polarized CAVB. The parameters of circularly polarized CAVB greatly affect the optical force. The longitudinal and transverse gradient force increase with the increase of decay factor and scaling factor, and decrease with the increase of the radius of the first primary ring and topological charges. The positions of the longitudinal stable equilibrium move toward the high numerical aperture lens when the scaling factor and the radius of the primary ring increase. The trapping range is broadened with the decrease of scaling factor. The optical orbital torque (OOT) of circularly polarized CAVB has circular symmetry and remains positive or negative. With the increase of topological charges, the peak value of OOT first increases and then decreases after reaches a maximum. These results are useful for optical trapping, optical levitation and particle acceleration.

Investigating tunneling process of atom exposed in circularly polarized strong-laser field

Science.gov (United States)

Yuan, MingHu; Xin, PeiPei; Chu, TianShu; Liu, HongPing

2017-03-01

We propose a method for studying the tunneling process by analyzing the instantaneous ionization rate of a circularly polarized laser. A numerical calculation shows that, for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obvious time delay phase shift of more than 190 attoseconds is observed. Further study shows that the atom has a longer tunneling time in the ionization under a shorter wavelength laser pulse. In our method, a Wigner rotation technique is employed to numerically solve the time-dependent Schrödinger equation of a single-active electron in a three-dimensional spherical coordinate system.

Investigating tunneling process of atom exposed in circularly polarized strong-laser field

International Nuclear Information System (INIS)

Yuan, MingHu; Xin, PeiPei; Liu, HongPing; Chu, TianShu

2017-01-01

We propose a method for studying the tunneling process by analyzing the instantaneous ionization rate of a circularly polarized laser. A numerical calculation shows that, for an atom exposed to a long laser pulse, if its initial electronic state wave function is non-spherical symmetric, the delayed phase shift of the ionization rate vs the laser cycle period in real time in the region close to the peak intensity of the laser pulse can be used to probe the tunneling time. In this region, an obvious time delay phase shift of more than 190 attoseconds is observed. Further study shows that the atom has a longer tunneling time in the ionization under a shorter wavelength laser pulse. In our method, a Wigner rotation technique is employed to numerically solve the time-dependent Schrödinger equation of a single-active electron in a three-dimensional spherical coordinate system. (paper)

Theoretical and numerical evaluation of polarimeter using counter-circularly-polarized-probing-laser under the coupling between Faraday and Cotton-Mouton effect.

Science.gov (United States)

Imazawa, Ryota; Kawano, Yasunori; Itami, Kiyoshi

2016-04-01

This study evaluated an effect of an coupling between the Faraday and Cotton-Mouton effect to a measurement signal of the Dodel-Kunz method which uses counter-circular-polarized probing-laser for measuring the Faraday effect. When the coupling is small (the Faraday effect is dominant and the characteristic eigenmodes are approximately circularly polarized), the measurement signal can be algebraically expressed and it is shown that the finite effect of the coupling is still significant. When the Faraday effect is not dominant, a numerical calculation is necessary. The numerical calculation under an ITER-like condition (Bt = 5.3 T, Ip = 15 MA, a = 2 m, ne = 10(20) m(-3) and λ = 119 μm) showed that difference between the pure Faraday rotation and the measurement signal of the Dodel-Kunz method was an order of one degree, which exceeds allowable error of ITER poloidal polarimeter. In conclusion, similar to other polarimeter techniques, the Dodel-Kunz method is not free from the coupling between the Faraday and Cotton-Mouton effect.

Analytical Solutions of Temporal Evolution of Populations in Optically-Pumped Atoms with Circularly Polarized Light

Directory of Open Access Journals (Sweden)

Heung-Ryoul Noh

2016-03-01

Full Text Available We present an analytical calculation of temporal evolution of populations for optically pumped atoms under the influence of weak, circularly polarized light. The differential equations for the populations of magnetic sublevels in the excited state, derived from rate equations, are expressed in the form of inhomogeneous second-order differential equations with constant coefficients. We present a general method of analytically solving these differential equations, and obtain explicit analytical forms of the populations of the ground state at the lowest order in the saturation parameter. The obtained populations can be used to calculate lineshapes in various laser spectroscopies, considering transit time relaxation.

Molecular frame photoemission: a probe of electronic/nuclear photo-dynamics and polarization state of the ionizing light

International Nuclear Information System (INIS)

Veyrinas, Kevin

2015-01-01

This is thesis is dedicated to the study and the use of the remarkable properties of the molecular frame photoelectron angular distribution (MFPAD). This observable is a very sensitive probe of both the photoionization (PI) processes in small molecules, through the determination of the magnitudes and relative phases of the dipole matrix elements, and the polarization state of the ionizing light, which is entirely encoded in the MFPAD in terms of the Stokes parameters (s1, s2, s3). MFPAD measurements take advantage of dissociative photoionization (DPI) processes by combining an electron-ion 3D momentum spectroscopy technique with the use of different radiation facilities: SOLEIL synchrotron (DESIRS and PLEIADES beamlines) and the XUV PLFA beamline (SLIC, LIDyL Attophysics group, CEA Saclay) based on the interaction of a strong laser field with a gaseous target called high harmonic generation (HHG). The first part of the thesis is devoted to the complete characterization of the polarization state of an incoming radiation. In this context, an original 'molecular polarimetry' method is introduced and demonstrated by comparison with a VUV optical polarimeter available on the DESIRS beamline. Using this method to determine the full polarization ellipse of HHG radiation generated in different conditions on the XUV PLFA facility leads to original results that include the challenging disentanglement of the circular and unpolarized components of the studied radiation. The second part deals with the study of DPI of the H 2 , D 2 and HD molecules induced by circularly polarized light at resonance with the doubly excited states Q1 and Q2. In this energy region (30-35 eV) where direct ionization, autoionization and dissociation compete on a femtosecond timescale, the photonic excitation gives rise to complex ultrafast electronic and nuclear coupled dynamics. The remarkable asymmetries observed in the circular dichroism in the molecular frame, compared to quantum

Multiple stable states of a periodically driven electron spin in a quantum dot using circularly polarized light

Science.gov (United States)

Korenev, V. L.

2011-06-01

The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. The same physics underlie the frequency-locking effect for two-color and mode-locked excitations. However, the pulsed excitation with mode-locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than 100 stable channels.

CHANG-ES - XI. Circular polarization in the cores of nearby galaxies

Science.gov (United States)

Irwin, Judith A.; Henriksen, Richard N.; WeŻgowiec, Marek; Damas-Segovia, Ancor; Wang, Q. Daniel; Krause, Marita; Heald, George; Dettmar, Ralf-Jürgen; Li, Jiang-Tao; Wiegert, Theresa; Stein, Yelena; Braun, Timothy T.; Im, Jisung; Schmidt, Philip; Macdonald, Scott; Miskolczi, Arpad; Merritt, Alison; Mora-Partiarroyo, S. C.; Saikia, D. J.; Sotomayor, Carlos; Yang, Yang

2018-06-01

We detect five galaxies in the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES) sample that show circular polarization (CP) at L band in our high-resolution data sets. Two of the galaxies (NGC 4388 and NGC 4845) show strong Stokes V/I ≡ mC ˜ 2 per cent, two (NGC 660 and NGC 3628) have values of mC ˜ 0.3 per cent, and NGC 3079 is a marginal detection at mC ˜ 0.2 per cent. The two strongest mC galaxies also have the most luminous X-ray cores and the strongest internal absorption in X-rays. We have expanded on our previous Faraday conversion interpretation and analysis and provide analytical expressions for the expected V signal for a general case in which the cosmic ray (CR) electron energy spectral index can take on any value. We provide examples as to how such expressions could be used to estimate magnetic field strengths and the lower energy cut-off for CR electrons. Four of our detections are resolved, showing unique structures, including a jet in NGC 4388 and a CP `conversion disc' in NGC 4845. The conversion disc is inclined to the galactic disc but is perpendicular to a possible outflow direction. Such CP structures have never before been seen in any galaxy to our knowledge. None of the galaxy cores show linear polarization at L band. Thus radio CP may provide a unique probe of the physical conditions in the cores of active galactic nuclei.

Polarization-controlled asymmetric excitation of surface plasmons

KAUST Repository

Xu, Quan

2017-08-28

Free-space light can be coupled into propagating surface waves at a metal–dielectric interface, known as surface plasmons (SPs). This process has traditionally faced challenges in preserving the incident polarization information and controlling the directionality of the excited SPs. The recently reported polarization-controlled asymmetric excitation of SPs in metasurfaces has attracted much attention for its promise in developing innovative plasmonic devices. However, the unit elements in these works were purposely designed in certain orthogonal polarizations, i.e., linear or circular polarizations, resulting in limited two-level polarization controllability. Here, we introduce a coupled-mode theory to overcome this limit. We demonstrated theoretically and experimentally that, by utilizing the coupling effect between a pair of split-ring-shaped slit resonators, exotic asymmetric excitation of SPs can be obtained under the x-, y-, left-handed circular, and right-handed circular polarization incidences, while the polarization information of the incident light can be preserved in the excited SPs. The versatility of the presented design scheme would offer opportunities for polarization sensing and polarization-controlled plasmonic devices.

Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

Directory of Open Access Journals (Sweden)

Xin Mi Yang

2015-12-01

Full Text Available Design of bandwidth-enhanced circularly polarized (CP patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM. In particular, the embedded meander line (EML structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

High Precision Linear And Circular Polarimetry. Sources With Stable Stokes Q,U & V In The Ghz Regime

Science.gov (United States)

Myserlis, Ioannis; Angelakis, E.; Zensus, J. A.

2017-10-01

We present a novel data analysis pipeline for the reconstruction of the linear and circular polarization parameters of radio sources. It includes several correction steps to minimize the effect of instrumental polarization, allowing the detection of linear and circular polarization degrees as low as 0.3 %. The instrumental linear polarization is corrected across the whole telescope beam and significant Stokes Q and U can be recovered even when the recorded signals are severely corrupted. The instrumental circular polarization is corrected with two independent techniques which yield consistent Stokes V results. The accuracy we reach is of the order of 0.1-0.2 % for the polarization degree and 1\\u00ba for the angle. We used it to recover the polarization of around 150 active galactic nuclei that were monitored monthly between 2010.6 and 2016.3 with the Effelsberg 100-m telescope. We identified sources with stable polarization parameters that can be used as polarization standards. Five sources have stable linear polarization; three are linearly unpolarized; eight have stable polarization angle; and 11 sources have stable circular polarization, four of which with non-zero Stokes V.

Angular momentum of circularly polarized light in dielectric media

Science.gov (United States)

Mansuripur, Masud

2005-07-01

A circularly polarized plane-wave is known to have no angular momentum when examined through Maxwell’s equations. This, however, contradicts the experimentally observed facts, where finite segments of plane waves are known to be capable of imparting angular momentum to birefringent platelets. Using a superposition of four plane-waves propagating at slightly different angles to a common direction, we derive an expression for the angular momentum density of a single plane-wave in the limit when the propagation directions of the four beams come into alignment. We proceed to use this four-beam technique to analyze the conservation of angular momentum when a plane-wave enters a dielectric slab from the free space. The angular momentum of the beam is shown to decrease upon entering the dielectric medium, by virtue of the fact that the incident beam exerts a torque on the slab surface at the point of entry. When the beam leaves the slab, it imparts an equal but opposite torque to the exit facet, thus recovering its initial angular momentum upon re-emerging into the free-space. Along the way, we derive an expression for the outward-directed force of a normally incident, finite-diameter beam on a dielectric surface; the possible relationship between this force and the experimentally observed bulging of a liquid surface under intense illumination is explored.

Photoinduced electric currents in ring-shaped molecules by circularly polarized laser pulses

International Nuclear Information System (INIS)

Nobusada, Katsuyuki; Yabana, Kazuhiro

2007-01-01

We have theoretically demonstrated that circularly polarized laser pulses induce electric currents and magnetic moments in ring-shaped molecules Na 10 and benzene. The time-dependent adiabatic local density approximation is employed for this purpose, solving the time-dependent Kohn-Sham equation in real space and real time. It has been found that the electric currents are induced efficiently and persist continuously even after the laser pulses were switched off provided the frequency of the applied laser pulse is in tune with the excitation energy of the electronic excited state with the dipole strength for each molecular system. The electric currents are definitely revealed to be a second-order nonlinear optical response to the magnitude of the electric field. The magnetic dipole moments inevitably accompany the ring currents, so that the molecules are magnetized. The production of the electric currents and the magnetic moments in the present procedure is found to be much more efficient than that utilizing static magnetic fields

Dynamics of a charged particle in a circularly polarized travelling electromagnetic wave. Self-consistent model for the wave-particle dynamical interaction

International Nuclear Information System (INIS)

Bourdier, A.

1999-01-01

This work concerns mainly the dynamics of a charged particle in an electromagnetic wave. It is a first step in elaborating a more general model permitting to predict the wave-particle interaction. We show how deriving a first integral gives an idea on how to create an electron current in a cold electron plasma. We present results which can be used to test the 2D and 3D Vlasov-Maxwell codes being built up in CEA-DAM. These codes will allow the calcination of the magnetic field created by an electromagnetic wave like the one due to the inverse Faraday effect when a circularly polarized wave drives the electrons of a plasma into circular orbits. (author)

Research on spectrum broadening covering visible light of a fiber femtosecond optical frequency comb for absolute frequency measurement

Science.gov (United States)

Xing, Shuai; Wu, Tengfei; Li, Shuyi; Xia, Chuanqing; Han, Jibo; Zhang, Lei; Zhao, Chunbo

2018-03-01

As a bridge connecting microwave frequency and optical frequency, femtosecond laser has important significance in optical frequency measurement. Compared with the traditional Ti-sapphire femtosecond optical frequency comb, with the advantages of compact structure, strong anti-interference ability and low cost, the fiber femtosecond optical frequency comb has a wider application prospect. An experiment of spectrum broadening in a highly nonlinear photonic crystal fiber pumped by an Er-fiber mode-locked femtosecond laser is studied in this paper. Based on optical amplification and frequency doubling, the central wavelength of the output spectrum is 780nm and the average power is 232mW. With the femtosecond pulses coupled into two different photonic crystal fibers, the coverage of visible spectrum is up to 500nm-960nm. The spectral shape and width can be optimized by changing the polarization state for satisfying the requirments of different optical frequencies measurement.

Research on the Scattering Characteristics and the RCS Reduction of Circularly Polarized Microstrip Antenna

Directory of Open Access Journals (Sweden)

W. Jiang

2013-01-01

Full Text Available Based on the study of the radiation and scattering of the circularly polarized (CP antenna, a novel radar cross-section (RCS reduction technique is proposed for CP antenna in this paper. Quasi-fractal slots are applied in the design of the antenna ground plane to reduce the RCS of the CP antenna. Both prototype antenna and array are designed, and their time-, frequency-, and space-domain characteristics are studied to authenticate the proposed technique. The simulated and measured results show that the RCS of the prototype antenna and array is reduced up to 7.85 dB and 6.95 dB in the band of 1 GHz–10 GHz. The proposed technique serves a candidate in the design of low RCS CP antennas and arrays.

Study of the ultrafast polarization dynamics in lithium borohydride by means of femtosecond X-ray diffraction

International Nuclear Information System (INIS)

Stingl, Johannes

2013-01-01

In this thesis the ultrafast electronic polarisation in the crystalline material lithium borohydride (LiBH 4 ) is examined. The material is excited by a femtosecond long optical pulse and scanned by a likewise short X-ray pulse. Using X-ray scattering the optically induced spatial rearrangement of electronic charge can be directly mapped with atomic spatial resolution. Copper K-alpha X-rays for the experiment are produced in a laboratory table-top laserplasma source with 1 kHz repetition rate. This radiation is then focused on a powdered sample. Debye-Scherrer rings produced from powder diffraction are collected on a large area detector and processed to yield intensity profiles. Using pump-probe technique the change in diffracted intensity, triggered by excitation with a femtosecond optical pulse is examined. The temporal resolution is given by the delay between pump and probe pulse. This way insight is gained into the dynamic electronic evolution of the system. Intensity changes can be correlated to changes in charge density in the relevant material to elucidate structural dynamics on the femtosecond time scale. Lithium borohydride was chosen since it displays necessary characteristics for the exploration of ultrafast electronic polarisation. Up to date there has been no spatially resolved research in the femtosecond regime elucidating this electronic phenomenon. This work presents the ultrafast resonse in Lithiumborhydrid (LiBH 4 ) to strong electronic fields with optical frequencies, which leads to charge relocation accompanied by electronic polarisation.

Polarized excitons and optical activity in single-wall carbon nanotubes

Science.gov (United States)

Chang, Yao-Wen; Jin, Bih-Yaw

2018-05-01

The polarized excitons and optical activity of single-wall carbon nanotubes (SWNTs) are studied theoretically by π -electron Hamiltonian and helical-rotational symmetry. By taking advantage of the symmetrization, the single-particle energy and properties of a SWNT are characterized with the corresponding helical band structure. The dipole-moment matrix elements, magnetic-moment matrix elements, and the selection rules can also be derived. Based on different selection rules, the optical transitions can be assigned as the parallel-polarized, left-handed circularly-polarized, and right-handed circularly-polarized transitions, where the combination of the last two gives the cross-polarized transition. The absorption and circular dichroism (CD) spectra are simulated by exciton calculation. The calculated results are well comparable with the reported measurements. Built on the foundation, magnetic-field effects on the polarized excitons and optical activity of SWNTs are studied. Dark-bright exciton splitting and interband Faraday effect in the CD spectrum of SWNTs under an axial magnetic field are predicted. The Faraday rotation dispersion can be analyzed according to the selection rules of circular polarizations and the helical band structure.

Optically Active CdSe-Dot/CdS-Rod Nanocrystals with Induced Chirality and Circularly Polarized Luminescence.

Science.gov (United States)

Cheng, Jiaji; Hao, Junjie; Liu, Haochen; Li, Jiagen; Li, Junzi; Zhu, Xi; Lin, Xiaodong; Wang, Kai; He, Tingchao

2018-05-30

Ligand-induced chirality in semiconductor nanocrystals (NCs) has attracted attention because of the tunable optical properties of the NCs. Induced circular dichroism (CD) has been observed in CdX (X = S, Se, Te) NCs and their hybrids, but circularly polarized luminescence (CPL) in these fluorescent nanomaterials has been seldom reported. Herein, we describe the successful preparation of l- and d-cysteine-capped CdSe-dot/CdS-rods (DRs) with tunable CD and CPL behaviors and a maximum anisotropic factor ( g lum ) of 4.66 × 10 -4 . The observed CD and CPL activities are sensitive to the relative absorption ratio of the CdS shell to the CdSe core, suggesting that the anisotropic g-factors in both CD and CPL increase to some extent for a smaller shell-to-core absorption ratio. In addition, the molar ratio of chiral cysteine to the DRs is investigated. Instead of enhancing the chiral interactions between the chiral molecules and DRs, an excess of cysteine molecules in aqueous solution inhibits both the CD and CPL activities. Such chiral and emissive NCs provide an ideal platform for the rational design of semiconductor nanomaterials with chiroptical properties.

Multiple-band reflective polarization converter using U-shaped metamaterial

International Nuclear Information System (INIS)

Huang, Xiaojun; Yang, Dong; Yang, Helin

2014-01-01

A multiple-band metamaterial reflective polarization converter (RPC) is proposed, which is composed of the dielectric substrate sandwiched with U-shaped metallic patterns and continuous metal film. The proposed U-shaped metamaterial RPC (UMM-RPC) can convert a linearly polarized wave to its cross polarized wave at the three resonant frequencies, which also can convert the linearly polarized wave to circularly polarized wave at other three resonant frequencies. Furthermore, the proposed UMM-RPC can maintain the same conversional direction at the three resonant frequencies when incident on a circularly polarized wave. The simulated and measured results are in agreement in the entire frequency range, and the polarization conversion ratio is over 90% for both linear and circular polarizations. The surface current distributions of the UMM-RPC are discussed to look into the physical mechanism. The proposed UMM-RPC has simple geometry but more operating frequency bands compared to the previous designs and can be used in applications such as antenna radome, remote sensors, and radiometer

Multiple-band reflective polarization converter using U-shaped metamaterial

Energy Technology Data Exchange (ETDEWEB)

Huang, Xiaojun [College of Physical Science and Technology, Central China Normal University, Wuhan 430079 (China); Department of Physics, Kashgar Teachers College, Kashgar 844000 (China); Yang, Dong [College of Physics and Electronics Science, Hubei Normal University, Huangshi 435002 (China); Yang, Helin, E-mail: emyang@mail.ccnu.edu.cn [College of Physical Science and Technology, Central China Normal University, Wuhan 430079 (China)

2014-03-14

A multiple-band metamaterial reflective polarization converter (RPC) is proposed, which is composed of the dielectric substrate sandwiched with U-shaped metallic patterns and continuous metal film. The proposed U-shaped metamaterial RPC (UMM-RPC) can convert a linearly polarized wave to its cross polarized wave at the three resonant frequencies, which also can convert the linearly polarized wave to circularly polarized wave at other three resonant frequencies. Furthermore, the proposed UMM-RPC can maintain the same conversional direction at the three resonant frequencies when incident on a circularly polarized wave. The simulated and measured results are in agreement in the entire frequency range, and the polarization conversion ratio is over 90% for both linear and circular polarizations. The surface current distributions of the UMM-RPC are discussed to look into the physical mechanism. The proposed UMM-RPC has simple geometry but more operating frequency bands compared to the previous designs and can be used in applications such as antenna radome, remote sensors, and radiometer.

Polarization-dependent pump-probe studies in atomic fine-structure levels: towards the production of spin-polarized electrons

International Nuclear Information System (INIS)

Sokell, E.; Zamith, S.; Bouchene, M.A.; Girard, B.

2000-01-01

The precession of orbital and spin angular momentum vectors has been observed in a pump-probe study of the 4P fine-structure states of atomic potassium. A femtosecond pump pulse prepared a coherent superposition of the two fine-structure components. A time-delayed probe pulse then ionized the system after it had been allowed to evolve freely. Oscillations recorded in the ion signal reflect the evolution of the orientation of the orbital and spin angular momentum due to spin-orbit coupling. This interpretation gives physical insight into the cause of the half-period phase shift observed when the relative polarizations of the laser pulses were changed from parallel to perpendicular. Finally, it is shown that these changes in the orientation of the spin momentum vector of the system can be utilized to produce highly spin-polarized free electrons on the femtosecond scale. (author)

Development and characterization of femtosecond laser driven soft x-ray lasers

International Nuclear Information System (INIS)

Bettaibi, I.

2005-06-01

Coherent soft x-ray sources have an important potential for scientific, medical and industrial applications. The development of high intensity laser systems allowed the realization of new coherent and fast soft x-ray sources like high order harmonic generation and soft x-ray lasers. These sources are compact, cheaper than traditional sources such as synchrotrons, and are thus interesting. This thesis presents the study of a new soft x-ray laser pumped by a femto-second laser beam working at 10 Hz. The circularly polarized ultra intense laser is longitudinally focused in a cell filled with xenon or krypton, to obtain the amplification of two lasing lines at 41.8 nm and 32.8 nm in Pd-like xenon and Ni-like krypton respectively. We carry out an experimental and numerical study of the source to understand the importance of different parameters such as the laser intensity and polarization, the gas pressure and the cell length. We have also spatially and temporally characterized the soft x-ray laser beam. To compensate the refraction of the driving laser we have investigated guiding techniques consisting in creating a plasma channel by electric discharge or using the multiple reflections of the driving laser on the internal walls of the dielectric tubes of sapphire or glass. A spectacular improvement of the source performances has been observed in both cases. Finally, we present a preliminary study on a different x-ray scheme: the inner shell photo pumping of neutral atoms. We have developed an optical system, which should create the appropriate conditions for the realisation of short wavelength x-ray amplifier. (author)

An electromagnetic helical undulator for polarized X-rays

International Nuclear Information System (INIS)

Gluskin, E.; Vinokurov, N.; Tcheskidov, V.; Medvedko, A.; Evtushenko, Y.; Kolomogorov, V.; Vobly, P.; Antokhin, E.; Ivanov, P.; Vasserman, I. B.; Trakhtenberg, E. M.; Den Hartog, P. K.; Deriy, B.; Erdmann, M.; Makarov, O.; Moog, E. R.

1999-01-01

Linearly and circularly polarized x-rays have been very successfully applied to the study of the properties of materials. Many applications can benefit from the availability of energy-turnable, high-brilliance x-ray beams with adjustable polarization properties. A helical undulator that can generate beams of variable (linear to circular) polarization has been designed and built by the Budker Institute of Nuclear Physics and the Advanced Photon Source. The first harmonic of this 12.8-cm-period device will cover the energy range from 0.4 keV to 3.5 keV. An important feature of this fully electromagnetic device is that it will allow one to generate 100% horizontally (K x =O)or vertically (K y =O) plane-polarized radiation, which will enable many experiments otherwise not technically feasible. With symmetric deflection parameters (K x =K y ), the on-axis radiation will be circularly polarized, with a user-selectable handedness. The polarization can be changed at rates up to 10 Hz

Polarization of fast neutrons in VVR-M reactor

International Nuclear Information System (INIS)

Garusov, E.A.; Lifshits, E.P.; Petrov, Yu.V.

1987-01-01

Neutron polarization in the reactor leads to circular polarization of γ quanta emitted both in radiational capture of neutrons and in the transition of nuclei excited as a result of inelastic scattering to the ground state. This may be used to determine the polarization of reactor neutrons. The circular polarization of γ quanta at light-water and graphite targets at the center of the active zone of the VVR-M reactor at the B.P. Konstantinov Leningrad Institute of Nuclear Physics was recently measured. A simplified experimental scheme is shown. Fast neutrons leaving the active zone of the reactor were excited in the inelastic scattering at the target nuclei. The polarization of the γ quanta emitted by nuclei in transitions to the ground state was measured by a polarimeter positioned above the active zone. The reason for the circular polarization of γ quanta may also be nonconservation of P parity on account of weak interaction in the capture of a neutron by hydrogen

Velocity Memory Effect for polarized gravitational waves

Science.gov (United States)

Zhang, P.-M.; Duval, C.; Gibbons, G. W.; Horvathy, P. A.

2018-05-01

Circularly polarized gravitational sandwich waves exhibit, as do their linearly polarized counterparts, the Velocity Memory Effect: freely falling test particles in the flat after-zone fly apart along straight lines with constant velocity. In the inside zone their trajectories combine oscillatory and rotational motions in a complicated way. For circularly polarized periodic gravitational waves some trajectories remain bounded, while others spiral outward. These waves admit an additional "screw" isometry beyond the usual five. The consequences of this extra symmetry are explored.

A stabilized optical frequency comb based on an Er-doped fiber femtosecond laser

Science.gov (United States)

Xia, Chuanqing; Wu, Tengfei; Zhao, Chunbo; Xing, Shuai

2018-03-01

An optical frequency comb based on a 250 MHz home-made Er-doped fiber femtosecond laser is presented in this paper. The Er-doped fiber laser has a ring cavity and operates mode-locked in femtosecond regime with the technique of nonlinear polarization rotation. The pulse duration is 118 fs and the spectral width is 30 nm. A part of the femtosecond laser is amplified in Er-doped fiber amplifier before propagating through a piece of highly nonlinear fiber for expanding the spectrum. The carrier-envelope offset frequency of the comb which has a signal-to-noise ratio more than 35 dB is extracted by means of f-2f beating. It demonstrates that both carrier-envelope offset frequency and repetition frequency keep phase locked to a Rubidium atomic clock simultaneously for 2 hours. The frequency stabilized fiber combs will be increasingly applied in optical metrology, attosecond pulse generation, and absolute distance measurement.

Comparison of characteristics of femtosecond laser-assisted anterior capsulotomy versus manual continuous curvilinear capsulorrhexis: A meta-analysis of 5-year results.

Science.gov (United States)

Ali, Muhammad Hassaan; Ullah, Samee; Javaid, Usman; Javaid, Mamoona; Jamal, Samreen; Butt, Nadeem Hafeez

2017-10-01

To perform a meta-analysis on the precision and safety of femtosecond laser-assisted anterior capsulotomy versus conventional manual continuous curvilinear capsulorrhexis. This meta-analysis was conducted from February 2010 to November 2014. Literature search on PubMed, Google Scholar, ExcerptaMedica database and Cochrane Library was done to identify randomised controlled trials and case-control studies. SPSS 20 was used for data analysis. Of the 10 articles included, there were 3(30%) randomised controlled trials and 7(70%) non-randomised controlled trials. The meta-analysis was based on a total of 2,882eyes. Of them, 1,498(51.97%) underwent femtosecond laser-assisted capsulotomy and 1,384(48.02%) underwent manual continuous curvilinear capsulorrhexis. The diameter of the capsulotomy and the rates of anterior capsule tear showed no statistical difference between the femtosecond laser group and the manual capsulorrhexis group (p=0.29 and p=0.68). In terms of circularity of capsulotomy, femtosecond laser group had a more significant advantage than the manual capsulorrhexis group (pmanual continuous curvilinear capsulorrhexis.

Polarization holographic optical recording of a new photochromic diarylethene

Science.gov (United States)

Pu, Shouzhi; Miao, Wenjuan; Chen, Anyin; Cui, Shiqiang

2008-12-01

A new symmetrical photochromic diarylethene, 1,2-bis[2-methyl-5-(3-methoxylphenyl)-3-thienyl]perfluorocyclopentene (1a), was synthesized, and its photochromic properties were investigated. The compound exhibited good photochromism both in solution and in PMMA film with alternating irradiation by UV/VIS light, and the maxima absorption of its closed-ring isomer 1b are 582 and 599 nm, respectively. Using diarylethene 1b/PMMA film as recording medium and a He-Ne laser (633 nm) for recording and readout, four types of polarization and angular multiplexing holographic optical recording were performed perfectly. For different types of polarization recording including parallel linear polarization recording, parallel circular polarization recording, orthogonal linear polarization recording and orthogonal circular polarization recording,have been accomplished successfully. The results demonstrated that the orthogonal circular polarization recording is the best method for polarization holographic optical recording when this compound was used as recording material. With angular multiplexing recording technology, two high contrast holograms were recorded in the same place on the film with the dimension of 0.78 μm2.

Perturbation approach to design of circularly polarised microstrip antennas

Science.gov (United States)

Lo, Y. T.; Richards, W. F.

1981-05-01

One of the most interesting applications of microstrip antennas is its use for transmitting or receiving circularly polarized (CP) waves. A description is given of a simple but accurate method to determine the critical dimensions needed to produce circular polarization for nearly square and nearly circular microstrip antennas. Shen (1981) in connection with the determination of the proper dimensions of an elliptical patch CP microstrip antenna first expressed the modal field in terms of Mathieu functions. To avoid the complicated numerical computation of the Mathieu functions, he approximated these functions in terms of Bessel functions. It is pointed out that the computation of Mathieu functions, or their approximate expressions can be avoided altogether if a perturbation method is applied to find the resonant frequencies of the two orthogonal modes. The implementation of this approach is demonstrated.

Large circular dichroism and optical rotation in titanium doped chiral silver nanorods

Energy Technology Data Exchange (ETDEWEB)

Titus, Jitto; Perera, A.G. Unil [Department of Physics and Astronomy, Optoelectronics Laboratory, GSU, Atlanta, GA (United States); Larsen, George; Zhao, Yiping [Department of Physics and Astronomy, Nanolab, UGA, Athens, GA (United States)

2016-10-15

The circular dichroism of titanium-doped silver chiral nanorod arrays grown using the glancing angle deposition (GLAD) method is investigated in the visible and near infrared ranges using transmission ellipsometry and spectroscopy. These films are found to have significant circular polarization effects across broad ranges of the visible to NIR spectrum, including large values for optical rotation. The characteristics of these circular polarization effects are strongly influenced by the morphology of the deposited arrays. Thus, the morphological control of the optical activity in these nanostructures demonstrates significant optimization capability of the GLAD technique for fabricating chiral plasmonic materials. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber

Science.gov (United States)

Chiang, W. Y.; Wu, M. H.; Wu, K. L.; Lin, M. H.; Teng, H. H.; Tsai, Y. F.; Ko, C. C.; Yang, E. C.; Jiang, J. A.; Barnett, L. R.; Chu, K. R.

2014-08-01

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

Pitch angle scattering of an energetic magnetized particle by a circularly polarized electromagnetic wave

International Nuclear Information System (INIS)

Bellan, P. M.

2013-01-01

The interaction between a circularly polarized wave and an energetic gyrating particle is described using a relativistic pseudo-potential that is a function of the frequency mismatch. Analysis of the pseudo-potential provides a means for interpreting numerical results. The pseudo-potential profile depends on the initial mismatch, the normalized wave amplitude, and the initial angle between the wave magnetic field and the particle perpendicular velocity. For zero initial mismatch, the pseudo-potential consists of only one valley, but for finite mismatch, there can be two valleys separated by a hill. A large pitch angle scattering of the energetic electron can occur in the two-valley situation but fast scattering can also occur in a single valley. Examples relevant to magnetospheric whistler waves show that the energetic electron pitch angle can be deflected 5°towards the loss cone when transiting a 10 ms long coherent wave packet having realistic parameters.

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber

Energy Technology Data Exchange (ETDEWEB)

Chiang, W. Y.; Wu, M. H.; Wu, K. L.; Lin, M. H.; Teng, H. H.; Barnett, L. R.; Chu, K. R., E-mail: krchu@yahoo.com.tw [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Tsai, Y. F.; Ko, C. C.; Yang, E. C. [Department of Entomology, National Taiwan University, Taipei, Taiwan (China); Jiang, J. A. [Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, Taipei, Taiwan (China)

2014-08-15

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber.

Science.gov (United States)

Chiang, W Y; Wu, M H; Wu, K L; Lin, M H; Teng, H H; Tsai, Y F; Ko, C C; Yang, E C; Jiang, J A; Barnett, L R; Chu, K R

2014-08-01

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

A polarization-insensitive plasmonic photoconductive terahertz emitter

KAUST Repository

Li, Xurong

2017-11-16

We present a polarization-insensitive plasmonic photoconductive terahertz emitter that uses a two-dimensional array of nanoscale cross-shaped apertures as the plasmonic contact electrodes. The geometry of the cross-shaped apertures is set to maximize optical pump absorption in close proximity to the contact electrodes. The two-dimensional symmetry of the cross-shaped apertures offers a polarization-insensitive interaction between the plasmonic contact electrodes and optical pump beam. We experimentally demonstrate a polarization-insensitive terahertz radiation from the presented emitter in response to a femtosecond optical pump beam and similar terahertz radiation powers compared to previously demonstrated polarization-sensitive photoconductive emitters with plasmonic contact electrode gratings at the optimum optical pump polarization.

Optically induced rotation of Rayleigh particles by vortex beams with different states of polarization

International Nuclear Information System (INIS)

Li, Manman; Yan, Shaohui; Yao, Baoli; Liang, Yansheng; Lei, Ming; Yang, Yanlong

2016-01-01

Optical vortex beams carry optical orbital angular momentum (OAM) and can induce an orbital motion of trapped particles in optical trapping. We show that the state of polarization (SOP) of vortex beams will affect the details of this optically induced orbital motion to some extent. Numerical results demonstrate that focusing the vortex beams with circular, radial or azimuthal polarizations can induce a uniform orbital motion on a trapped Rayleigh particle, while in the focal field of the vortex beam with linear polarization the particle experiences a non-uniform orbital motion. Among the formers, the vortex beam with circular polarization induces a maximum optical torque on the particle. Furthermore, by varying the topological charge of the vortex beams, the vortex beam with circular polarization gives rise to an optimum torque superior to those given by the other three vortex beams. These facts suggest that the circularly polarized vortex beam is more suitable for rotating particles. - Highlights: • States of polarization of vortex beams affect the optically induced orbital motion of particles. • The dependences of the force and orbital torque on the topological charge, the size and the absorptivity of particles were calculated. • Focused vortex beams with circular, radial or azimuthal polarizations induce a uniform orbital motion on particles. • Particles experience a non-uniform orbital motion in the focused linearly polarized vortex beam. • The circularly polarized vortex beam is a superior candidate for rotating particles.

Analysis of Resistive-Vee Dipole Antennas for Producing Polarization Diversity

Science.gov (United States)

2014-08-01

3 1.2 Existing Circular Polarization GPR Technologies . . . . . . . . . . . . . 4 1.2.1 Crossed-Dipole Antennas...8 1.3 Proposed Circular Polarization GPR System . . . . . . . . . . . . . . . . 10 1.4 Outline...reshaped RVD with the Kim resistive profile is marked by the square. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Figure 89

Study of the parity violation in nuclei - Circular polarization of photons emitted in a nuclear transition

International Nuclear Information System (INIS)

Desplanques, Bertrand.

1975-01-01

Many experiments have shown parity violation in nuclear forces and a theoretical interpretation of these results should give some information on the weak interaction. The present work has to do with the calculation of the circular polarization of photons emitted in the transitions 5/2 + →7/2 + in 181 Ta and 9/2 - →7/2 + in 175 Lu. This calculation has been done by employing a good description of the final and initial states and in particular by including the effects of the short and long range correlations. The results so obtained differ somewhat from those obtained previously with a simpler nuclear model and seem to favor weak interaction models with a large ΔT=1 component [fr

Determination of femtosecond-laser-induced refractive-index changes in an optical fiber from far-field measurements

DEFF Research Database (Denmark)

Savolainen, Juha-Matti; Grüner-Nielsen, Lars; Kristensen, Poul

2014-01-01

A new method for direct writing of localized, circularly symmetric refractive-index changes in optical fibers with a femtosecond laser is demonstrated. The refractive-index changes are characterized using a novel approach employing comparison of numerical simulations to the measured far......-field profiles of unmodified and modified fibers. From the analysis, a negative refractive-index change of −0.015 0.005 within a radius of 0.6 0.1 μm is determined....

Source of spin polarized electrons

International Nuclear Information System (INIS)

Pierce, D.T.; Meier, F.A.; Siegmann, H.C.

1976-01-01

A method is described of producing intense beams of polarized free electrons in which a semiconductor with a spin orbit split valence band and negative electron affinity is used as a photocathode and irradiated with circularly polarized light

Polarization of the coherent radio emission from pulsars

International Nuclear Information System (INIS)

Ardavan, H.

1982-01-01

The polarization characteristics of the radiation from a quasi-steady pulsar magnetosphere are calculated using the amplitude-modulated-noise interpretation of the data on pulse structures. The total emission consists of three incoherently mixed radiation streams. Two of the independent polarization states are elliptically polarized (modes I and II) and one is linearly polarized (mode III). In the regime where the length scale of the radial distribution of the electric current density is appreciably longer than the wavelength of the radiation, the position angles of modes I and II are orthogonal and those of modes I and III coincident. However, the senses of circular polarization of modes I and II are in general uncorrelated. The degrees of circular polarization of the 'orthogonal' modes are decreasing functions of frequency and both approach zero in the limit where the frequency of the radiation is much higher than the rotation frequency of the pulsar. Longitudinal changes in the position angle and in the sense of circular polarization of each of the elliptically polarized modes are shown to arise, together with mode transitions, in part from the stochastic fluctuations and in part from the systematic variations of the electric current density with the azimuthal angle, in a narrow emitting region adjacent to the light cylinder. (author)

Femtosecond laser-induced cross-periodic structures on a crystalline silicon surface under low pulse number irradiation

Science.gov (United States)

Ji, Xu; Jiang, Lan; Li, Xiaowei; Han, Weina; Liu, Yang; Wang, Andong; Lu, Yongfeng

2015-01-01

A cross-patterned surface periodic structure in femtosecond laser processing of crystalline silicon was revealed under a relatively low shots (4 energy slightly higher than the ablation threshold. The experimental results indicated that the cross-pattern was composed of mutually orthogonal periodic structures (ripples). Ripples with a direction perpendicular to laser polarization (R⊥) spread in the whole laser-modified region, with the periodicity around 780 nm which was close to the central wavelength of the laser. Other ripples with a direction parallel to laser polarization (R‖) were found to be distributed between two of the adjacent ripples R⊥, with a periodicity about the sub-wavelength of the irradiated laser, 390 nm. The geometrical morphology of two mutually orthogonal ripples under static femtosecond laser irradiation could be continuously rotated as the polarization directions changed, but the periodicity remained almost unchanged. The underlying physical mechanism was revealed by numerical simulations based on the finite element method. It was found that the incubation effect with multiple shots, together with the redistributed electric field after initial ablation, plays a crucial role in the generation of the cross-patterned periodic surface structures.

3D electrostatic actuator fabricated by non-ablative femtosecond laser exposure and chemical etching

Directory of Open Access Journals (Sweden)

Yang Tao

2015-01-01

Full Text Available We demonstrate the novel design of an electrostatic micro-actuator based on monolithic three-dimensional (3D shapes fabricated by non-ablative femtosecond laser exposure combined with chemical etching. Further, we present a single-scan stacking approach exploited in the fabrication of the 3D actuator to create crack-free, highcontrast, high fidelity and integrated micro-structures. Influential parameters: energy per pulse, polarization, scanning spacing and stacking directionwere systematically studied to predict and control the etching rate of 3D planes.Finally, we report the characterization of the actuator and its potential application in optomechanics to show a complete scenario of femtosecond laser machined integrated 3D micro-systems incorporating multiple functionalities.

Dynamical behaviour of FEL devices operating with two undulators having opposite circular polarizations

Energy Technology Data Exchange (ETDEWEB)

Dattoli, G. [ENEA, Divisione Fisica Applicata, Centro Ricerche Frascati, Rome (Italy); Ottaviani, P.L. [ENEA, Divisione Fisica Applicata, Centro Ricerche, Bologna (Italy); Bucci, L. [ENEA, Guest Rome (Italy)

2000-07-01

Optical-Klystron FELs operating with undulators having opposite circular polarizations are characterized by a spontaneous emission spectrum which does not exhibit the characteristic interference pattern. The use of the Madey theorem may allow the conclusion that, for such configuration, the dispersive section does not provide any gain enhancement. In this paper it has been analyzed the problem from a dynamical point of view and clarify how the optical field evolve, what is the role of the bunching and how the consequences of the Madey theorem should be correctly understood. [Italian] Klystron ottici operanti con ondulatori aventi polarizzazione elicoidali opposte, sono caratterizzati da uno spettro di emissione spontanea senza il termine interferenziale dovuto alla sezione dispersiva. L'uso del teorema di Madey indurrebbe alla conclusione che, per una tale configurazione, la sezione dispersiva non induce nessun aumento del guadagno. In questo lavoro analizziamo il problema da un punto di vista dinamico che chiarisce l'evoluzione del campo ottico, quale e' il ruolo del bunching e come le conseguenze del teorema di Madey debbano essere interpretate.

Optical properties of polarization-dependent geometrical phase elements with partially polarized light

International Nuclear Information System (INIS)

Gorodetski, Y.; Biener, G.; Niv, A.; Kleiner, V.; Hasman, E.

2005-01-01

Full Text:The behavior of geometrical phase elements illuminated with partially polarized monochromatic beams is being theoretically as well as experimentally investigated. The element discussed in this paper is composed of wave plates with retardation and space-variant orientation angle. We found that a beam emerging from such an element comprises two polarization orders of right and left-handed circularly polarized states with conjugate geometrical phase modification. This phase equals twice the orientation angle of the space-variant wave plate comprising the element. Apart from the two polarization orders, the emerging beam coherence polarization matrix comprises a matrix termed as the vectorial interference matrix. This matrix contains the information concerning the correlation between the two orthogonal circularly polarized portions of the incident beam. In this paper we measure this correlation by a simple interference experiment. Furthermore, we found that the equivalent mutual intensity of the emerging beam is being modulated according to the geometrical phase induced by the element. Other interesting phenomena along propagation will be discussed theoretically and experimentally demonstrated. We demonstrate experimentally our analysis by using a spherical geometrical phase element, which is realized by use of space-variant sub wavelength grating and illuminated with a CO 2 laser radiation of 10.6μm wavelength

Inducing elliptically polarized high-order harmonics from aligned molecules with linearly polarized femtosecond pulses

DEFF Research Database (Denmark)

Etches, Adam; Madsen, Christian Bruun; Madsen, Lars Bojer

2010-01-01

A recent paper reported elliptically polarized high-order harmonics from aligned N2 using a linearly polarized driving field [X. Zhou et al., Phys. Rev. Lett. 102, 073902 (2009)]. This observation cannot be explained in the standard treatment of the Lewenstein model and has been ascribed to many...

Giant Circular Dichroism in Individual Carbon Nanotubes Induced by Extrinsic Chirality

Directory of Open Access Journals (Sweden)

A. Yokoyama

2014-01-01

Full Text Available Circular dichroism is widely used for characterizing organic and biological materials, but measurements at a single-molecule level are challenging because differences in absorption for opposite helicities are small. Here, we show that extrinsic chirality can induce giant circular dichroism in individual carbon nanotubes, with the degree of polarization reaching 65%. The signal has a large dependence on the incidence angle, consistent with extrinsic-chirality-induced effects in which symmetry is broken by the optical wave vector. We propose that the field-induced charge distribution on the substrate results in an efficient polarization conversion, giving rise to the giant dichroism. Our results highlight the possibility of polarization manipulation at the nanoscale for applications in integrated photonics and novel metamaterial designs.

Photoanisotropic polarization gratings beyond the small recording angle regime

NARCIS (Netherlands)

Xu, M.; De Boer, D.K.G.; Van Heesch, C.M.; Wachters, A.J.H.; Urbach, H.P.

2010-01-01

Polarization gratings can be realized by polarization holographic recording in photoanisotropic materials. In this paper, we study two types of polarization gratings. One is recorded with two orthogonally circularly (OC) polarized beams and the other one with two orthogonally linearly (OL) polarized

ELECTROMAGNETIC SCATTERING AND ANTENNA TECHNOLOGY (EMSAT) Task Order 0003: Design of a Circularly Polarized, 20 60 GHZ Active Phased Array for Wide Angle Scanning

Science.gov (United States)

2017-08-08

previously published linear -to-circular polarizers. This is because the first sheet has a low inductance in the -direction, which acts as a wire-grid...GHZ Active Phased Array for Wide Angle Scanning Carl R. Pfeiffer Defense Engineering Corporation Boris Tomasic Multispectral Sensing and...GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62204F/61102F 6. AUTHOR(S) Carl R. Pfeiffer (Defense Engineering Corporation) Boris Tomasic (AFRL

Light-induced circular birefringence in cyanoazobenzene side-chain liquid-crystalline polyester films

DEFF Research Database (Denmark)

Naydenova, I; Nikolova, L; Ramanujam, P.S.

1999-01-01

We report the inducement of large circular birefringence (optical activity) in films of a cyanoazobenzene side-chain liquid-crystalline polyester on illumination with circularly polarized light. The polyester has no chiral groups and is initially isotropic. The induced optical rotation is up to 5...

Polarity-inverted lateral overgrowth and selective wet-etching and regrowth (PILOSWER) of GaN.

Science.gov (United States)

Jang, Dongsoo; Jue, Miyeon; Kim, Donghoi; Kim, Hwa Seob; Lee, Hyunkyu; Kim, Chinkyo

2018-03-07

On an SiO 2 -patterned c-plane sapphire substrate, GaN domains were grown with their polarity controlled in accordance with the pattern. While N-polar GaN was grown on hexagonally arranged circular openings, Ga-polar GaN was laterally overgrown on mask regions due to polarity inversion occurring at the boundary of the circular openings. After etching of N-polar GaN on the circular openings by H 3 PO 4 , this template was coated with 40-nm Si by sputtering and was slightly etched by KOH. After slight etching, a thin layer of Si left on the circular openings of sapphire,but not on GaN, was oxidized during thermal annealing and served as a dielectric mask during subsequent regrowth. Thus, the subsequent growth of GaN was made only on the existing Ga-polar GaN domains, not on the circular openings of the sapphire substrate. Transmission electron microscopy analysis revealed no sign of threading dislocations in this film. This approach may help fabricating an unholed and merged GaN film physically attached to but epitaxially separated from the SiO 2 -patterned sapphire.

Multi-image mosaic with SIFT and vision measurement for microscale structures processed by femtosecond laser

Science.gov (United States)

Wang, Fu-Bin; Tu, Paul; Wu, Chen; Chen, Lei; Feng, Ding

2018-01-01

In femtosecond laser processing, the field of view of each image frame of the microscale structure is extremely small. In order to obtain the morphology of the whole microstructure, a multi-image mosaic with partially overlapped regions is required. In the present work, the SIFT algorithm for mosaic images was analyzed theoretically, and by using multiple images of a microgroove structure processed by femtosecond laser, a stitched image of the whole groove structure could be studied experimentally and realized. The object of our research concerned a silicon wafer with a microgroove structure ablated by femtosecond laser. First, we obtained microgrooves at a width of 380 μm at different depths. Second, based on the gray image of the microgroove, a multi-image mosaic with slot width and slot depth was realized. In order to improve the image contrast between the target and the background, and taking the slot depth image as an example, a multi-image mosaic was then realized using pseudo color enhancement. Third, in order to measure the structural size of the microgroove with the image, a known width streak ablated by femtosecond laser at 20 mW was used as a calibration sample. Through edge detection, corner extraction, and image correction for the streak images, we calculated the pixel width of the streak image and found the measurement ratio constant Kw in the width direction, and then obtained the proportional relationship between a pixel and a micrometer. Finally, circular spot marks ablated by femtosecond laser at 2 mW and 15 mW were used as test images, and proving that the value Kw was correct, the measurement ratio constant Kh in the height direction was obtained, and the image measurements for a microgroove of 380 × 117 μm was realized based on a measurement ratio constant Kw and Kh. The research and experimental results show that the image mosaic, image calibration, and geometric image parameter measurements for the microstructural image ablated by

A femtosecond Yb-doped fiber laser with generalized vector vortex beams output (Conference Presentation)

Science.gov (United States)

Huo, Tiancheng; Qi, Li; Zhang, Buyun; Chen, Zhongping

2017-03-01

Light carries both spin and orbital angular momentum (OAM) and the superpositions of these two dynamical properties have found many applications. Many techniques exist to create such light sources but none allow their creation at the femtosecond fiber laser. Here we report on a novel mode-locked Ytterbium-doped fiber laser that generates femtosecond pulses with generalized vector vortex states. The controlled generation of such pulses such as azimuthally and radially polarized light with definite orbital angular momentum modes are demonstrated. A unidirectional ring cavity constructed with the Yb-doped fiber placed at the end of the fiber section to reduces unnecessary nonlinear effects is employed for self-starting operation. Pairs of diffraction gratings are used for compensating the normal group velocity dispersion of the fiber and other elements. Mode-locked operation is achieved based on nonlinear polarization evolution, which is mainly implemented with the single mode fiber, the bulk wave plates and the variable spiral plates (q-plate with topological charge q=0.5). The conversion from spin angular momentum to the OAM and reverse inside the laser cavity are realized by means of a quarter-wave plate and a q-plate so that the polarization control was mapped to OAM mode control. The fiber laser is diode pumped by a wavelength-division multiplexing coupler, which leads to excellent stability and portability.

Chiral Binaphthylbis(4,4'-Bipyridin-1-Ium)/Cucurbit[8]Uril Supramolecular System and Its Induced Circularly Polarized Luminescence.

Science.gov (United States)

Chen, Xu-Man; Chen, Yong; Liang, Lu; Liu, Qiu-Jun; Liu, Yu

2018-05-01

Circularly polarized luminescence (CPL) induced by host-guest complexation remains a challenge in supramolecular chemistry. Herein, a couple of CPL-silent enantiomeric guest binaphthylbis(4,4'-bipyridinium) salts can emit obvious CPL in the presence of cucurbit[8]uril in aqueous media, due to the restriction of molecular rotation limitation effect. Such CPL can be reversibly adjusted by the addition of acid and base. Furthermore, the resultant supramolecular systems can interact with DNA, accompanied by the morphological conversion from branched supramolecular nanowires to exfoliated nanowires, which can enable to the exploration of such supramolecular systems as DNA markers by CPL signals. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

Energy Technology Data Exchange (ETDEWEB)

Higley, Daniel J., E-mail: dhigley@stanford.edu; Yuan, Edwin [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Hirsch, Konstantin; Dakovski, Georgi L.; Jal, Emmanuelle; Lutman, Alberto A.; Coslovich, Giacomo; Hart, Philip; Hoffmann, Matthias C.; Mitra, Ankush; Moeller, Stefan; Ohldag, Hendrik; Seaberg, Matthew; Stöhr, Joachim; Nuhn, Heinz-Dieter; Reid, Alex H.; Dürr, Hermann A.; Schlotter, William F. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Liu, Tianmin; MacArthur, James P. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); and others

2016-03-15

X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L{sub 3,2}-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

Proposed method to produce a highly polarized e+ beam for future linear colliders

International Nuclear Information System (INIS)

Okugi, Toshiyuki; Chiba, Masami; Kurihara, Yoshimasa

1996-01-01

We propose a method to produce a spin-polarized e + beam using e + e - pair-creation by circularly polarized photons. Assuming Compton scattering of an unpolarized e - beam and circularly polarized laser light, scattered γ-rays at the high end of the energy spectrum are also circularly polarized. If those γ-rays are utilized to create e ± pairs on a thin target, the spin-polarization is preserved for e + 's at the high end of their energy spectrum. By using the injector linac of Accelerator Test Facility at KEK and a commercially available Nd:YAG pulse laser, we can expect about 10 5 polarized e + 's per second with a degree of polarization of 80% and a kinetic energy of 35-80 MeV. The apparatus for creation and measurement of polarized e + 's is being constructed. We present new idea for possible application of our method to future linear colliders by utilizing a high-power CO 2 laser. (author)

Polarization Nonlinear Optics of Quadratically Nonlinear Azopolymers

International Nuclear Information System (INIS)

Konorov, S.O.; Akimov, D.A.; Ivanov, A.A.; Petrov, A.N.; Alfimov, M.V.; Yakimanskii, A.V.; Smirnov, N.N.; Ivanova, V.N.; Kudryavtsev, V.V.; Podshivalov, A.A.; Sokolova, I.M.; Zheltikov, A.M.

2005-01-01

The polarization properties of second harmonic and sum-frequency signals generated by femtosecond laser pulses in films of polymers containing covalent groups of an azobenzothiazole chromophore polarized by an external electric field are investigated. It is shown that the methods of polarization nonlinear optics make it possible to determine the structure of oriented molecular dipoles and reveal important properties of the motion of collectivized πelectrons in organic molecules with strong optical nonlinearities. The polarization measurements show that the tensor of quadratic nonlinear optical susceptibility of chromophore fragments oriented by an external field in macromolecules of the noted azopolymers has a degenerate form. This is indicative of a predominantly one-dimensional character of motion of collectivized π electrons along an extended group of atoms in such molecules

A Gamma Polarimeter for Neutron Polarization Measurement in a Liquid Deuterium Target for Parity Violation in Polarized Neutron Capture on Deuterium.

Science.gov (United States)

Komives, A; Sint, A K; Bowers, M; Snow, M

2005-01-01

A measurement of the parity-violating gamma asymmetry in n-D capture would yield information on N-N parity violation independent of the n-p system. Since cold neutrons will depolarize in a liquid deuterium target in which the scattering cross section is much larger than the absorption cross section, it will be necessary to quantify the loss of polarization before capture. One way to do this is to use the large circular polarization of the gamma from n-D capture and analyze the circular polarization of the gamma in a gamma polarimeter. We describe the design of this polarimeter.

Design Concept of Superconducting Multipole Wiggler with Variably Polarized X-Ray

International Nuclear Information System (INIS)

Hwang, C.S.; Chang, C.H.; Li, W.P.; Lin, F.Y.

2004-01-01

In response to the growing demand for X-ray research, and to satisfy future needs for generating circularly polarized synchrotron radiation in the X-ray region, a 3.5 T superconducting multipole with a periodic length of 6 cm was designed to produce horizontal linearly polarized, and circularly polarized light on a 1.5 GeV electron storage ring. Differently arranged excitation current loop for the same coil design switched between the operation of symmetric and asymmetric modes to creat the linearly and circularly polarized light, respectively. This study elucidates the design concepts of the superconducting multipole wiggler with symmetric and asymmetric operation modes. The design of the magnetic circuit and the field calculation are also discussed. Meanwhile, the spectra characteristics of the symmetric and asymmetric modes are calculated and presented in this article

SCRLH-TL Based Sequential Rotation Feed Network for Broadband Circularly Polarized Antenna Array

Directory of Open Access Journals (Sweden)

B. F. Zong

2016-04-01

Full Text Available In this paper, a broadband circularly polarized (CP microstrip antenna array using composite right/left-handed transmission line (SCRLH-TL based sequential rotation (SR feed network is presented. The characteristics of a SCRLH-TL are initially investigated. Then, a broadband and low insertion loss 45º phase shifter is designed using the SCRLH-TL and the phase shifter is employed in constructing a SR feed network for CP antenna array. To validate the design method of the SR feed network, a 2×2 antenna array comprising sequentially rotated coupled stacked CP antenna elements is designed, fabricated and measured. Both the simulated and measured results indicate that the performances of the antenna element are further enhanced when the SR network is used. The antenna array exhibits the VSWR less than 1.8 dB from 4 GHz to 7 GHz and the 3 dB axial ratio (AR from 4.4 GHz to 6.8 GHz. Also, high peak gain of 13.7 dBic is obtained. Besides, the normalized radiation patterns at the operating frequencies are symmetrical and the side lobe levels are low at φ=0º and φ=90º.

Tunable femtosecond Cherenkov fiber laser

DEFF Research Database (Denmark)

Liu, Xiaomin; Svane, Ask Sebastian; Lægsgaard, Jesper

2014-01-01

We demonstrate electrically-tunable femtosecond Cherenkov fiber laser output at the visible range. Using an all-fiber, self-starting femtosecond Yb-doped fiber laser as the pump source and nonlinear photonic crystal fiber link as the wave-conversion medium, ultrafast, milliwatt-level, tunable...... and spectral isolated Cherenkov radiation at visible wavelengths are reported. Such a femtosecond Cherenkov laser source is promising for practical biophotonics applications....

Superconducting Undulator with Variably Polarized Light

CERN Document Server

Hwang, Ching Shiang; Ching Fan, Tai; Li, W P; Lin, P H

2004-01-01

This study investigates planar in-vacuo superconducting undulators with periodic length of 5 cm (IVSU5) producing linearly and circularly polarized infrared rays or xrays source. The vertically wound racetrack coil is selected for the coil and pole fabrication of the IVSU5. When the up and down magnetic pole arrays with alternative directions rotated wires in the horizontal plane, a helical field radiates circularly polarized light in the electron storage ring, the free electron laser (FEL), and the energy recovery linac (ERL) facilities. Meanwhile, an un-rotated wire is constructed together with the rotated wire on the same undulator is used to switch the linear horizontal and vertical, the right- and left-circular polarization radiation. Given a periodic length of 5 cm and a gap of 23 mm, the maximum magnetic flux density in the helical undulator are Bz = 1.5 T and Bx = 0.5 T when the wires rotated by 20°. This article describes the main factors of the planar and helical undulator design for FEL and...

Ultrafast S1 and ICT state dynamics of a marine carotenoid probed by femtosecond one- and two-photon pump-probe spectroscopy

International Nuclear Information System (INIS)

Kosumi, Daisuke; Kusumoto, Toshiyuki; Fujii, Ritsuko; Sugisaki, Mitsuru; Iinuma, Yoshiro; Oka, Naohiro; Takaesu, Yuki; Taira, Tomonori; Iha, Masahiko; Frank, Harry A.; Hashimoto, Hideki

2011-01-01

Ultrafast relaxation kinetics of fucoxanthin in polar and non-polar solvents have been studied by femtosecond pump-probe spectroscopy. Transient absorption associated with S 1 or intramolecular charge transfer (ICT) excited state has been observed following either one-photon excitation to the optically allowed S 2 state or two-photon excitation to the symmetry-forbidden S 1 state. The results suggest that the ICT state formed after excitation of fucoxanthin in a polar solvent is a distinct excited state from S 1 .

Circularly polarized luminescence of helically assembled pyrene π-stacks on RNA and DNA duplexes.

Science.gov (United States)

Nakamura, Mitsunobu; Ota, Fuyuki; Takada, Tadao; Akagi, Kazuo; Yamana, Kazushige

2018-05-01

In this report, we describe the circularly polarized luminescence (CPL) of the RNA duplexes having one to four 2'-O-pyrene modified uridines (Upy) and the DNA duplexes having two, four, and six pyrene modified non-nucleosidic linkers (Py). Both the pyrene π-stack arrays formed on the RNA and DNA double helical structures exhibited pyrene excimer fluorescence. In the pyrene-modified RNA systems, the RNA duplex having four Upys gives CPL emission with g lum value of <0.01 at 480 nm. The structure of pyrene stacks on the RNA duplex may be rigidly regulated with increase in the Upy domains, which resulted in the CPL emission. In the DNA systems, the pyrene-modified duplexes containing two and four Pys exhibited CPL emission with g lum values of <0.001 at 505 nm. The pyrene π-stack arrays presented here show CPL emission. However, the g lum values are relatively small when compared with our previous system consisting of the pyrene-zipper arrays on RNA. © 2018 Wiley Periodicals, Inc.

Chiroptical methods in a wide wavelength range for obtaining Ln3+ complexes with circularly polarized luminescence of practical interest.

Science.gov (United States)

Górecki, Marcin; Carpita, Luca; Arrico, Lorenzo; Zinna, Francesco; Di Bari, Lorenzo

2018-05-29

We studied enantiopure chiral trivalent lanthanide (Ln3+ = La3+, Sm3+, Eu3+, Gd3+, Tm3+, and Yb3+) complexes with two fluorinated achiral tris(β-diketonate) ligands (HFA = hexafluoroacetylacetonate and TTA = 2-thenoyltrifluoroacetonate), incorporating a chiral bis(oxazolinyl)pyridine (PyBox) unit as a neutral ancillary ligand, by the combined use of optical and chiroptical methods, ranging from UV to IR both in absorption and circular dichroism (CD), and including circularly polarized luminescence (CPL). Ultimately, all the spectroscopic information is integrated into a total and a chiroptical super-spectrum, which allows one to characterize a multidimensional chemical space, spanned by the different Ln3+ ions, the acidity and steric demand of the diketone and the chirality of the PyBox ligand. In all cases, the Ln3+ ions endow the systems with peculiar chiroptical properties, either allied to f-f transitions or induced by the metal onto the ligand. In more detail, we found that Sm3+ complexes display interesting CPL features, which partly superimpose and partly integrate the more common Eu3+ properties. Especially, in the context of security tags, the pair Sm/Eu may be a winning choice for chiroptical barcoding.

Reconfigurable micromachined antenna with polarization diversity for mm-wave applications

KAUST Repository

Sallam, Mai O.

2012-03-01

In this paper a novel MEMS antenna with reconfigurable polarization operating at 60 GHz is presented. This antenna can provide vertical linear polarization, horizontal linear polarization, left hand circular polarization (LHCP), or right hand circular polarization (RHCP) based on the states of the switches present in the feeding network. The proposed antenna is characterized by having its radiating elements isolated from the feeding circuitry via a ground plane without the need for wafer bonding or hybrid integration. Such advantage results in good electric performance while maintains low fabrication cost. The antenna parameters are optimized using HFSS and the results are cross-validated using CST. The good agreement between the two simulators, confirms that the proposed antenna enjoys attractive radiation characteristics for all polarization senses. © 2012 IEEE.

Reconfigurable micromachined antenna with polarization diversity for mm-wave applications

KAUST Repository

Sallam, Mai O.; Soliman, Ezzeldin A.; Sedky, Sherif

2012-01-01

In this paper a novel MEMS antenna with reconfigurable polarization operating at 60 GHz is presented. This antenna can provide vertical linear polarization, horizontal linear polarization, left hand circular polarization (LHCP), or right hand circular polarization (RHCP) based on the states of the switches present in the feeding network. The proposed antenna is characterized by having its radiating elements isolated from the feeding circuitry via a ground plane without the need for wafer bonding or hybrid integration. Such advantage results in good electric performance while maintains low fabrication cost. The antenna parameters are optimized using HFSS and the results are cross-validated using CST. The good agreement between the two simulators, confirms that the proposed antenna enjoys attractive radiation characteristics for all polarization senses. © 2012 IEEE.

1-MHz high power femtosecond Yb-doped fiber chirped-pulse amplifier

Science.gov (United States)

Hu, Zhong-Qi; Yang, Pei-Long; Teng, Hao; Zhu, Jiang-Feng; Wei, Zhi-Yi

2018-01-01

A practical femtosecond polarization-maintaining Yb-doped fiber amplifier enabling 153 fs transform-limited pulse duration with 32 μJ pulse energy at 1 MHz repetition rate corresponding to a peak power of 0.21 GW is demonstrated. The laser system based on chirped-pulse amplification (CPA) technique is seeded by a dispersion managed, nonlinear polarization evolution (NPE) mode-locked oscillator with spectrum bandwidth of 31 nm at 1040 nm and amplified by three fiber pre-amplifying stages and a rod type fiber main amplifying stage. The laser works with beam quality of M2 of 1.3 and power stability of 0.63% (root mean square, RMS) over 24 hours will be stable sources for industrial micromachining, medical therapy and scientific research.

A helical optical for circular polarized UV-FEL project at the UVSOR

Energy Technology Data Exchange (ETDEWEB)

Hama, Hiroyuki [Institute for Molecular Science, Okazaki (Japan)

1995-12-31

Most of existing storage ring free electron lasers (SRFEL) are restricted those performances by degradation of mirrors in optical cavities. In general, the SRFEL gain at the short wavelength region with high energy electrons is quite low, and the high reflectivity mirrors such as dielectric multilayer mirrors are therefore required. The mirror degradation is considered as a result of irradiation of higher harmonic photons that are simultaneously emitted from planar optical klystron (OK) type undulators, which are commonly used in SRFEL. This problem is getting severer as the lasing wavelength becomes shorter. The UVSOR-FEL had been originally scheduled to be shutdown by 1996 because another undulator project for spectroscopic studies with circular polarized photon would take the FEL`s place. According to suggestion of the insertion device group of the SPring-8, we have designed a helical undulator that is able to vary degree and direction of the polarization easily. In addition, the undulator can be converted into a helical OK by replacing magnets at the center part of undulator in order to coexist with further FEL experiments. Using a calculated magnetic field for magnet configurations of the OK mode, the radiation spectrum at wide wavelength range was simulated by a Fourier transform of Lienard-Wiechert potentials. As a matter of course, some higher harmonics are radiated on the off-axis angle. However it was found out that the higher harmonics is almost negligible as far as inside a solid angle of the Gaussian laser mode. Moreover the gain at the UV region of 250 nm is expected to be much higher than our present FEL because of high brilliant fundamental radiation. The calculated spatial distribution of higher harmonics and the estimated instantaneous gain is presented. Advantages of the helical OK for SRFEL will be discussed in view of our experience, and a possibility of application two-color experiment with SR will be also mentioned.

Development of polarization magneto-optics of paramagnetic crystals

International Nuclear Information System (INIS)

Zapasskij, V.S.; Feofilov, P.P.

1975-01-01

The present status of the polarization magnetooptics of crystals containing paramagnetic ion impurities is reviewed. The paper discusses methods of measurement of circular magnetic anisotropy and results obtained in recent years in the field of conventional magnetooptical studies, e.g., magnetooptical activity in absorption spectra for intrinsic and impurity defects in crystals, luminescence magnetic circular polarization, anisotropy of magnetooptical activity in cubic crystals. The main emphasis is placed on new trends in polarization magnetooptics: studies of interactions of a spin system with a lattice, in particular, spin-lattice relaxation and spin memory effect, experiments in the double radiooptical resonance, studies of optical spin relaxation, nonlinear magnetooptical effects, etc

Design Studies for Flux and Polarization Measurements of Photons and Positrons for SLAC Proposal E166: An experiment to test polarized positron production in the FFTB (LCC-0107)

Energy Technology Data Exchange (ETDEWEB)

Woods, M

2003-10-02

We present results from design studies carried out to investigate measurements of the flux, spectrum and polarization of undulator photons for SLAC Proposal E166. A transmission Compton polarimeter is considered for measuring the photon circular polarization. We also present results for measuring the flux and spectrum of positrons produced by the undulator photons in an 0.5X{sub 0} Titanium target. And we present some considerations for use of a transmission Compton polarimeter to measure the circular polarization of bremsstrahlung photons emitted by the polarized positrons in a thin radiator.

A New Approach to Suppress the Effect of Machining Error for Waveguide Septum Circular Polarizer at 230 GHz Band in Radio Astronomy

Science.gov (United States)

Hasegawa, Yutaka; Harada, Ryohei; Tokuda, Kazuki; Kimura, Kimihiro; Ogawa, Hideo; Onishi, Toshikazu; Nishimura, Atsushi; Han, Johnson; Inoue, Makoto

2017-05-01

A new stepped septum-type waveguide circular polarizer (SST-CP) was developed to operate in the 230 GHz band for radio astronomy, especially submillimeter-band VLBI observations. For previously reported SST-CP models, the 230 GHz band is too high to achieve the design characteristics in manufactured devices because of unexpected machining errors. To realize a functional SST-CP that can operate in the submillimeter band, a new method was developed, in which the division surface is shifted from the top step of the septum to the second step from the top, and we simulated the expected machining error. The SST-CP using this method can compensate for specified machining errors and suppress serious deterioration. To verify the proposed method, several test pieces were manufactured, and their characteristics were measured using a VNA. These results indicated that the insertion losses were approximately 0.75 dB, and the input return losses and the crosstalk of the left- and right-hand circular polarization were greater than 20 dB at 220-245 GHz on 300 K. Moreover, a 230 GHz SST-CP was developed by the proposed method and installed in a 1.85-m radio telescope receiver systems, and then had used for scientific observations during one observation season without any problems. These achievements demonstrate the successful development of a 230 GHz SST-CP for radio astronomical observations. Furthermore, the proposed method can be applicable for observations in higher frequency bands, such as 345 GHz.

Acceleration of polarized particles

International Nuclear Information System (INIS)

Buon, J.

1992-05-01

The spin kinetics of polarized beams in circular accelerators is reviewed in the case of spin-1/2 particles (electrons and protons) with emphasis on the depolarization phenomena. The acceleration of polarized proton beams in synchrotrons is described together with the cures applied to reduce depolarization, including the use of 'Siberian Snakes'. The in-situ polarization of electrons in storage rings due to synchrotron radiation is studied as well as depolarization in presence of ring imperfections. The applications of electron polarization to accurately calibrate the rings in energy and to use polarized beams in colliding-beam experiments are reviewed. (author) 76 refs., 19 figs., 1 tab

A polarized photoluminescence study of strained layer GaAs photocathodes

International Nuclear Information System (INIS)

Mair, R.A.

1996-07-01

Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ∼0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, ∼78 K and ∼12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16±.21 eV, b = -2.00±.05 eV and d = -4.87±.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data

Spatially periodic structures, under femtosecond pulsed excitation of crystals

International Nuclear Information System (INIS)

Martynovitch, Evgueni F.; Petite, Guillaume; Dresvianski, Vladimir P.; Starchenko, Anton A.

2004-01-01

Measuring the luminescence intensity of specially prepared irradiation defects induced in crystals, we observe that the longitudinal structure of quasi-interferences induced by two orthogonally polarized femtosecond pulses propagating together with different velocities is insensitive to the spatial broadening due to velocity dispersion in the crystals. On the contrary, it does depend on the pulse duration when it is changed by varying the spectral width of the radiation. It thus allows a direct measurement of the coherence time of such pulses. Stability of the axial selectivity is a good sign, taking away a number of serious limitations concerning possible applications

Compton polarimetry detection of small circularly and linearly polarized impurities in Mössbauer 8.4 keV (3/2-1/2) M1 γ-transition of {sup 169}Tm

Energy Technology Data Exchange (ETDEWEB)

Tsinoev, V.; Cherepanov, V.; Shuvalov, V.; Balysh, A.; Gabbasov, R., E-mail: graul@list.ru [National Research Centre “Kurchatov Institute” (Russian Federation)

2016-12-15

The arrangement of an experiment to detect the P−odd and P, T−odd polarized part of the Mössbauer ({sup +}3/2– {sup +}1/2) gamma transition of a deformed {sup 169}Tm nucleus with an energy of 8.4 keV by Compton polarimetry is discussed. Tm {sub 2}O{sub 3} single crystal with a quadrupolarly split Mössbauer spectrum is proposed as a resonance polarizer. A Be-scatterer-based Compton polarimeter and a synchronously detecting system will be used to measure the P-odd circular polarization P{sub C}and P, T-odd linear polarization P{sub L}.The expected accuracy of measuring the relative magnitude of the P, T-odd contribution is about 1% of the magnitude of usual weak nucleon–nucleon interaction.

Linear polarized fluctuations in the cosmic microwave background

International Nuclear Information System (INIS)

Partridge, R.B.; Nowakowski, J.; Martin, H.M.

1988-01-01

We report here limits on the linear (and circular) polarization of the cosmic microwave background on small angular scales, 18''≤ θ ≤ 160''. The limits are based on radio maps of Stokes parameters and polarisation (linear and circular). (author)

Polarized wiggler for NSLS x-ray ring design considerations

International Nuclear Information System (INIS)

Friedman, A.; Krinsky, S.; Blum, E.

1992-03-01

We examine the properties of an elliptically polarized wiggler that will generate circularly polarized photons with energy spectrum of 3--12 KeV. The vertical wiggler magnetic field is produced by permanent magnets while the horizontal wiggler field is generated by electric coils capable of AC excitation. The radiation parameters of the wiggler are presented, including photon flux, circular and linear polarization and spectrum. These parameters are compared to the synchrotron radiation from a bending magnet. Numerical values are calculated for radiation from the wiggler and bending magnet for the NSLS X-ray ring parameters. A conceptual design for such a wiggler is discussed and several different alternatives are analyzed. We consider AC excitation of the wiggler to produce the time modulation of the elliptic polarization, and also to produce time modulated linearly polarized radiation

Investigation of the polarization state of dual APPLE-II undulators.

Science.gov (United States)

Hand, Matthew; Wang, Hongchang; Dhesi, Sarnjeet S; Sawhney, Kawal

2016-01-01

The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used.

Femtosecond versus nanosecond laser machining: comparison of induced stresses and structural changes in silicon wafers

International Nuclear Information System (INIS)

Amer, M.S.; El-Ashry, M.A.; Dosser, L.R.; Hix, K.E.; Maguire, J.F.; Irwin, Bryan

2005-01-01

Laser micromachining has proven to be a very successful tool for precision machining and microfabrication with applications in microelectronics, MEMS, medical device, aerospace, biomedical, and defense applications. Femtosecond (FS) laser micromachining is usually thought to be of minimal heat-affected zone (HAZ) local to the micromachined feature. The assumption of reduced HAZ is attributed to the absence of direct coupling of the laser energy into the thermal modes of the material during irradiation. However, a substantial HAZ is thought to exist when machining with lasers having pulse durations in the nanosecond (NS) regime. In this paper, we compare the results of micromachining a single crystal silicon wafer using a 150-femtosecond and a 30-nanosecond lasers. Induced stress and amorphization of the silicon single crystal were monitored using micro-Raman spectroscopy as a function of the fluence and pulse duration of the incident laser. The onset of average induced stress occurs at lower fluence when machining with the femtosecond pulse laser. Induced stresses were found to maximize at fluence of 44 J cm -2 and 8 J cm -2 for nanosecond and femtosecond pulsed lasers, respectively. In both laser pulse regimes, a maximum induced stress is observed at which point the induced stress begins to decrease as the fluence is increased. The maximum induced stress was comparable at 2.0 GPa and 1.5 GPa for the two lasers. For the nanosecond pulse laser, the induced amorphization reached a plateau of approximately 20% for fluence exceeding 22 J cm -2 . For the femtosecond pulse laser, however, induced amorphization was approximately 17% independent of the laser fluence within the experimental range. These two values can be considered nominally the same within experimental error. For femtosecond laser machining, some effect of the laser polarization on the amount of induced stress and amorphization was also observed

Cutting thin glass by femtosecond laser ablation

Science.gov (United States)

Shin, Hyesung; Kim, Dongsik

2018-06-01

The femtosecond laser ablation process for cutting thin aluminoborosilicate glass sheets of thickness 100 μm was investigated with emphasis on effective cutting speed (Veff) and mechanical strength of diced samples. The process parameters including the laser fluence (F), overlap ratio (r) of the laser beam and polarization direction were varied at a fixed pulse repetition rate f = 1 kHz to find the optimal process condition that maximizes Veff and edge strength. A three-point bending test was performed to evaluate the front-side and back-side bending (edge) strength of the laser-cut samples. Veff was proportional to F unless r exceeded a critical value, at which excessive energy began to be delivered at the same spot. The front-side edge strength was bigger than the back-side strength because of the back-side damages such as chipping. Good edge strength, as high as ∼280 MPa (front-side) and ∼230 MPa (back-side), was obtained at F = 19 J/m2, r = 0.99, with laser polarization vertical to the cutting path.

Formation of periodic mesoscale structures arranged in a circular symmetry at the silicon surface exposed to radiation of a single femtosecond laser pulse

Energy Technology Data Exchange (ETDEWEB)

Romashevskiy, S.A., E-mail: sa.romashevskiy@gmail.com [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation); Ashitkov, S.I.; Ovchinnikov, A.V. [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation); Kondratenko, P.S. [Nuclear Safety Institute of the Russian Academy of Sciences, Bol' shaya Tul' skaya st. 53, Moscow 115191 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region 141700 (Russian Federation); Agranat, M.B. [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation)

2016-06-30

Graphical abstract: - Highlights: • Single pulse irradiation of silicon gave rise to the periodic mesoscale structures. • The number of the periodic structures depends on the incident laser fluence. • The theory of periodically modulated absorption of laser energy is proposed. - Abstract: The periodic mesoscale structures arranged in a circular symmetry were found at the silicon surface exposed to radiation of the single femtosecond laser pulse with a Gaussian intensity profile in the ambient air conditions. These peculiar structures have the appearance of the protrusions of ∼10 nm height and of ∼600 nm width (at a FWHM) separately located inside the ablated region with a period of the incident laser wavelength. It was found that their position at the surface corresponds to the specified laser intensity slightly above the ablation threshold. The number of the formed periodic structures varies with the fluence of the incident laser pulse and in our experiments it was found to have changed from one to eleven. We suppose that formation of these mesoscale structures is caused by heating of a microscale volume to the strongly defined temperature. The theoretical model was proposed to explain the obtained data. It assumes that the interference of incident laser radiation with laser-induced surface electromagnetic waves results in generation of periodic distribution of electron temperature. Thus formation of the periodic structures at the specified laser intensity is attributed to periodically modulated absorption of laser energy at a focal laser spot.

Polarimetric purity and the concept of degree of polarization

Science.gov (United States)

Gil, José J.; Norrman, Andreas; Friberg, Ari T.; Setälä, Tero

2018-02-01

The concept of degree of polarization for electromagnetic waves, in its general three-dimensional version, is revisited in the light of the implications of the recent findings on the structure of polarimetric purity and of the existence of nonregular states of polarization [J. J. Gil et al., Phys Rev. A 95, 053856 (2017), 10.1103/PhysRevA.95.053856]. From the analysis of the characteristic decomposition of a polarization matrix R into an incoherent convex combination of (1) a pure state Rp, (2) a middle state Rm given by an equiprobable mixture of two eigenstates of R, and (3) a fully unpolarized state Ru -3 D, it is found that, in general, Rm exhibits nonzero circular and linear degrees of polarization. Therefore, the degrees of linear and circular polarization of R cannot always be assigned to the single totally polarized component Rp. It is shown that the parameter P3 D proposed formerly by Samson [J. C. Samson, Geophys. J. R. Astron. Soc. 34, 403 (1973), 10.1111/j.1365-246X.1973.tb02404.x] takes into account, in a proper and objective form, all the contributions to polarimetric purity, namely, the contributions to the linear and circular degrees of polarization of R as well as to the stability of the plane containing its polarization ellipse. Consequently, P3 D constitutes a natural representative of the degree of polarimetric purity. Some implications for the common convention for the concept of two-dimensional degree of polarization are also analyzed and discussed.

Ultrafast S{sub 1} and ICT state dynamics of a marine carotenoid probed by femtosecond one- and two-photon pump-probe spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kosumi, Daisuke, E-mail: kosumi@sci.osaka-cu.ac.j [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Kusumoto, Toshiyuki [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Fujii, Ritsuko; Sugisaki, Mitsuru [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka (Japan); Iinuma, Yoshiro; Oka, Naohiro; Takaesu, Yuki; Taira, Tomonori; Iha, Masahiko [South Product Co. Ltd., 12-75 Suzaki, Uruma-shi, Okinawa 904-2234 (Japan); Frank, Harry A. [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Hashimoto, Hideki, E-mail: hassy@sci.osaka-cu.ac.j [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka (Japan)

2011-03-15

Ultrafast relaxation kinetics of fucoxanthin in polar and non-polar solvents have been studied by femtosecond pump-probe spectroscopy. Transient absorption associated with S{sub 1} or intramolecular charge transfer (ICT) excited state has been observed following either one-photon excitation to the optically allowed S{sub 2} state or two-photon excitation to the symmetry-forbidden S{sub 1} state. The results suggest that the ICT state formed after excitation of fucoxanthin in a polar solvent is a distinct excited state from S{sub 1}.

High resolution polarimetry of the Sun at 3. 7 and 11. 1 cm wavelengths. [Stokes parameters, polarization

Energy Technology Data Exchange (ETDEWEB)

Lang, K R [Tufts Univ., Medford, Mass. (USA). Dept. of Physics

1977-04-01

The four Stokes parameters are presented for interferometric observations of the Sun at wavelengths of lambda=3.7 cm and lambda=11 cm with angular resolutions between 2.7 and 36.7 seconds of arc. An H..cap alpha.. solar flare of importance SN and type C has a radio wavelength (lambda=3.7 cm) size of 5 seconds of arc, a flux density of 0.3 x 10/sup -22/Wm/sup -2/Hz/sup -1/, and a brightness temperature on the order of 10/sup 7/K. The radio flare is 30% left circularly polarized at lambda=3.7 cm, 70% left circularly polarized at lambda=11 cm, and no detectable linear polarization was observed at either wavelength. During a forty hour observation of sunspot region McMath No 13926 no substantial variations in circular polarization were observed, whereas one hour prior to the eruption of a solar flare dramatic changes in circular polarization were observed. Small scale features whose angular sizes are on the order of five seconds of arc exhibit changes of circular polarization of up to 80%. At times other than those immediately preceding flare emission, the degree of circular polarization was the same as the two wavelengths but the sign was reversed. This situation can be explained if magnetic fields of intensity H<=1000 G and electron densities of Nsub(e)>=10/sup 7/cm/sup -3/ are present.

Polarized proton beams

International Nuclear Information System (INIS)

Roser, T.

1995-01-01

The acceleration of polarized proton beams in circular accelerators is complicated by the presence of numerous depolarizing spin resonances. Careful and tedious minimization of polarization loss at each of these resonances allowed acceleration of polarized proton beams up to 22 GeV. It has been the hope that Siberian Snakes, which are local spin rotators inserted into ring accelerators, would eliminate these resonances and allow acceleration of polarized beams with the same ease and efficiency that is now routine for unpolarized beams. First tests at IUCF with a full Siberian Snake showed that the spin dynamics with a Snake can be understood in detail. The author now has results of the first tests of a partial Siberian Snake at the AGS, accelerating polarized protons to an energy of about 25 GeV. These successful tests of storage and acceleration of polarized proton beams open up new possibilities such as stored polarized beams for internal target experiments and high energy polarized proton colliders

Circularly polarized triple band glass shaped monopole patch antenna with metallic reflector for bluetooth & wireless applications

Science.gov (United States)

Jangid, K. G.; Choudhary, N.; Jain, P.; Sharma, B. R.; Saini, J. S.; Kulhar, V. S.; Bhatnagar, D.

2016-03-01

This paper presents the design and performance of strip line fed glass shaped monopole patch antenna having with overall size 30mm × 30 mm × 1.59 mm. In the patch; an eight shaped slot and in the ground plane an eight shaped ring are introduced. A metallic ground plane is also introduced at appropriate location beneath the ground plane. The proposed antenna is simulated by applying CST Microwave Studio simulator. Antenna provides circularly polarized radiations, triple broad impedance bandwidth of 203MHz (2.306GHz to 2.510GHz), 42MHz (2.685GHz to 2.757GHz) & GHz (3.63 GHz to 6.05 GHz), high flat gain (close to 5dBi) and good radiation properties in the desired frequency range. This antenna may be a very useful tool for 2.45GHz Bluetooth communication band as well as for 2.4GHz/5.2 GHz /5.8 GHz WLAN bands & 3.7GHz/5.5 GHz Wi-Max bands.

Dirac electron in a chiral space-time crystal created by counterpropagating circularly polarized plane electromagnetic waves

Science.gov (United States)

Borzdov, G. N.

2017-10-01

The family of solutions to the Dirac equation for an electron moving in an electromagnetic lattice with the chiral structure created by counterpropagating circularly polarized plane electromagnetic waves is obtained. At any nonzero quasimomentum, the dispersion equation has two solutions which specify bispinor wave functions describing electron states with different energies and mean values of momentum and spin operators. The inversion of the quasimomentum results in two other linearly independent solutions. These four basic wave functions are uniquely defined by eight complex scalar functions (structural functions), which serve as convenient building blocks of the relations describing the electron properties. These properties are illustrated in graphical form over a wide range of quasimomenta. The superpositions of two basic wave functions describing different spin states and corresponding to (i) the same quasimomentum (unidirectional electron states with the spin precession) and (ii) the two equal-in-magnitude but oppositely directed quasimomenta (bidirectional electron states) are also treated.

Femtosecond laser spectroscopy

CERN Document Server

Hannaford, Peter

2005-01-01

As concepts and methodologies have evolved over the past two decades, the realm of ultrafast science has become vast and exciting and has impacted many areas of chemistry, biology and physics, and other fields such as materials science, electrical engineering, and optical communication. The field has recently exploded with the announcement of a series of remarkable new developments and advances. This volume surveys this recent growth in eleven chapters written by leading international researchers in the field. It includes sections on femtosecond optical frequency combs, soft x-ray femtosecond laser sources, and attosecond laser sources. In addition, the contributors address real-time spectroscopy of molecular vibrations with sub-5-fs pulses and multidimensional femtosecond coherent spectroscopies for studying molecular and electron dynamics. Novel methods for measuring and characterizing ultrashort laser pulses and ultrashort pulses of light are also described. The topics covered are revolutionizing the field...

Femtosecond Laser Filamentation

CERN Document Server

Chin, See Leang

2010-01-01

Femtosecond Laser Filamentation gives a comprehensive review of the physics of propagation of intense femtosecond laser pulses in optical media (principally air) and the applications and challenges of this new technique. This book presents the modern understanding of the physics of femtosecond laser pulse propagation, including unusual new effects such as the self-transformation of the pulse into a white light laser pulse, intensity clamping, the physics of multiple filamentation and competition, and how filaments’ ability to melt glass leads to wave guide writing. The potential applications of laser filamentation in atmospheric sensing and the generation of other electromagnetic pulses from the UV to the radio frequency are treated, together with possible future challenges in the excitation of super-excited states of molecules. Exciting new phenomena such as filament induced ultrafast birefringence and the excitation of molecular rotational wave packets and their multiple revivals in air (gases) will also ...

Linearly polarized photons at ELSA

Energy Technology Data Exchange (ETDEWEB)

Eberhardt, Holger [Physikalisches Institut, Universitaet Bonn (Germany)

2009-07-01

To investigate the nucleon resonance regime in meson photoproduction, double polarization experiments are currently performed at the electron accelerator ELSA in Bonn. The experiments make use of a polarized target and circularly or linearly polarized photon beams. Linearly polarized photons are produced by coherent bremsstrahlung from an accurately aligned diamond crystal. The orientation of the crystal with respect to the electron beam is measured using the Stonehenge-Technique. Both, the energy of maximum polarization and the plane of polarization, can be deliberately chosen for the experiment. The linearly polarized beam provides the basis for the measurement of azimuthal beam asymmetries, such as {sigma} (unpolarized target) and G (polarized target). These observables are extracted in various single and multiple meson photoproduction channels.

Multiscale deformations lead to high toughness and circularly polarized emission in helical nacre-like fibres.

Science.gov (United States)

Zhang, Jia; Feng, Wenchun; Zhang, Huangxi; Wang, Zhenlong; Calcaterra, Heather A; Yeom, Bongjun; Hu, Ping An; Kotov, Nicholas A

2016-02-24

Nacre-like composites have been investigated typically in the form of coatings or free-standing sheets. They demonstrated remarkable mechanical properties and are used as ultrastrong materials but macroscale fibres with nacre-like organization can improve mechanical properties even further. The fiber form or nacre can, simplify manufacturing and offer new functional properties unknown yet for other forms of biomimetic materials. Here we demonstrate that nacre-like fibres can be produced by shear-induced self-assembly of nanoplatelets. The synergy between two structural motifs--nanoscale brick-and-mortar stacking of platelets and microscale twisting of the fibres--gives rise to high stretchability (>400%) and gravimetric toughness (640 J g(-1)). These unique mechanical properties originate from the multiscale deformation regime involving solid-state self-organization processes that lead to efficient energy dissipation. Incorporating luminescent CdTe nanowires into these fibres imparts the new property of mechanically tunable circularly polarized luminescence. The nacre-like fibres open a novel technological space for optomechanics of biomimetic composites, while their continuous spinning methodology makes scalable production realistic.

Enhancement of third-order harmonic generation by interaction of two IR femtosecond filaments

International Nuclear Information System (INIS)

Liu, Z Y; Ding, P J; Shi, Y C; Lu, X; Liu, Q C; Sun, S H; Ding, B W; Hu, B T; Liu, X L

2012-01-01

Three orders of magnitude in the enhancement of the third-order harmonic (TH) generation induced by the interaction of two femtosecond filaments crossing with small angles in the air is achieved. The dependences of the TH generation on the time delay, the relative polarization, the input laser intensity ratios between the probe and pump beam are measured with the crossing angle of 3.5deg , and the results with quasi-vertical crossing angle are also shown for comparison

Circular intensity differential scattering (CIDS) measurements in the soft x-ray region of the spectrum (∼16 eV to 500 eV)

International Nuclear Information System (INIS)

Maestre, M.F.; Bustamante, C.; Snyder, P.; Rowe, E.; Hansen, R.

1991-03-01

We propose the use of recently developed techniques of circular intensity differential scattering (CIDS), as extended to the soft x-ray region of the spectrum (16 eV to 500 eV), to study the higher order organization of the eukaryotic chromosome. CIDS is the difference in scattering power of an object when illuminated by right circularly polarized vs. left circularly polarized electromagnetic radiation of arbitrary wavelength. CIDS has been shown to be a very sensitive measure of the helical organization of the scattering object eg. the eukaryotic chromosome. Preliminary results of measurements of samples of bacteriophages and octopus sperm done at SRC, Wisconsin, show the technique to be very sensitive to the dimensional parameters of the particles interrogated by circularly polarized light. 7 refs., 5 figs

Design and implementation of VUV-CD and LD measurements using an ac modulated polarizing undulator

International Nuclear Information System (INIS)

Yagi-Watanabe, K.; Yamada, T.; Tanaka, M.; Kaneko, F.; Kitada, T.; Ohta, Y.; Nakagawa, K.

2005-01-01

VUV circular dichroism (CD) and linear dichroism (LD) have been successfully measured at wavelengths beyond the conventional limit by using an ac modulated polarizing undulator. We have developed CD and LD measuring technique by polarization modulation at the source, without using transmission type polarizing modulator, to extend to the coverage to wavelengths shorter than 140-bar nm. AIST developed in 1986 ac polarizing undulator by using a electron storage ring 'TERAS' based on an original concept. The undulator which can produce any desired polarization of vertical- and horizontal-linear polarization (VLP and HLP) and right- and left-handed circular polarization (RCP and LCP) is specially well suited to both measurements of CD and LD. With this undulator, the polarization alternate in the order of VLP-RCP-HLP-RCP-VLP-LCP-HLP-LCP-VLP-, i.e. when circular polarization is modulated in f Hz, linear polarization alters in 2f Hz. This allows us simultaneous measurements of CD and LD. Since the TERAS can produce ac-modulated polarized radiation of wavelength as short as 40-bar nm, it is expected to have CD and LD measurement extended to 40-bar nm

Single-Layer, Dual-Port, Dual-Band, and Orthogonal-Circularly Polarized Microstrip Antenna Array with Low Frequency Ratio

Directory of Open Access Journals (Sweden)

Min Wang

2018-01-01

Full Text Available A single-layer, dual-port, dual-band, and dual circularly polarized (CP microstrip array is designed for satellite communication in this paper. The operating frequencies are 8.2 and 8.6 GHz with a very low ratio of 1.05. First, a rectangular patch element is fed through microstrip lines at two orthogonal edges to excite two orthogonal dominant modes of TM01 and TM10. The very low frequency ratio can be realized with high polarization isolations. Then, a 2-by-2 dual-band dual-CP subarray is constructed by two independent sets of sequentially rotated (SR feed structures. An 8-by-8 array is designed on the single-layer thin substrate. Finally, by utilizing one-to-four power dividers and semirigid coaxial cables, a 16-by-16 array is developed to achieve higher gain. Measured results show that the 16-by-16 array has 15 dB return loss (RL bandwidths of 4.81% and 6.75% and 3 dB axial ratio (AR bandwidths of 2.84% and 1.57% in the lower and the upper bands, respectively. Isolations of 18.6 dB and 19.4 dB and peak gains of 25.1 dBic and 25.6 dBic are obtained at 8.2 and 8.6 GHz, respectively.

A pulsed laser polarization monitor for PEP

International Nuclear Information System (INIS)

Prescott, C.

1975-01-01

Back scattered circularly polarized laser photons are considered as a monitor for electron beam polarization. The up-down asymmetry of up to 10 percent can be measured using a wire ionization chamber with submillimeter resolution. With a pulsed laser backgrounds are to expected to be large

Acceleration of polarized proton beams

International Nuclear Information System (INIS)

Roser, T.

1998-01-01

The acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian snakes are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible. A similar scheme is being studied for the 800 GeV HERA proton accelerator

Guiding of laser pulses in plasma waveguides created by linearly-polarized femtosecond laser pulses

OpenAIRE

Lemos, N.; Cardoso, L.; Geada, J.; Figueira, G.; Albert, F.; Dias, J. M.

2018-01-01

We experimentally demonstrate that plasma waveguides produced with ultra-short laser pulses (sub-picosecond) in gas jets are capable of guiding high intensity laser pulses. This scheme has the unique ability of guiding a high-intensity laser pulse in a plasma waveguide created by the same laser system in the very simple and stable experimental setup. A hot plasma column was created by a femtosecond class laser that expands into an on-axis parabolic low density profile suitable to act as a wav...

Investigation of the polarization state of dual APPLE-II undulators

International Nuclear Information System (INIS)

Hand, Matthew; Wang, Hongchang; Dhesi, Sarnjeet S.; Sawhney, Kawal

2016-01-01

Complete polarization analysis of the photon beam produced by a dual APPLE-II undulator configuration using a multilayer-based soft X-ray polarimeter is given. The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used

Investigation of the polarization state of dual APPLE-II undulators

Energy Technology Data Exchange (ETDEWEB)

Hand, Matthew; Wang, Hongchang, E-mail: hongchang.wang@diamond.ac.uk; Dhesi, Sarnjeet S.; Sawhney, Kawal [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom)

2016-01-01

Complete polarization analysis of the photon beam produced by a dual APPLE-II undulator configuration using a multilayer-based soft X-ray polarimeter is given. The use of an APPLE II undulator is extremely important for providing a high-brilliance X-ray beam with the capability to switch between various photon beam polarization states. A high-precision soft X-ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single-period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used.

Erbium:ytterbium fiber-laser system delivering watt-level femtosecond pulses using divided pulse amplification

Science.gov (United States)

Herda, Robert; Zach, Armin

2015-03-01

We present an Erbium:Ytterbium codoped fiber-amplifer system based on Divided-Pulses-Amplification (DPA) for ultrashort pulses. The output from a saturable-absorber mode-locked polarization-maintaining (PM) fiber oscillator is amplified in a PM normal-dispersion Erbium-doped fiber. After this stage the pulses are positively chirped and have a duration of 2.0 ps at an average power of 93 mW. A stack of 5 birefringent Yttrium-Vanadate crystals divides these pulses 32 times. We amplify these pulses using a double-clad Erbium:Ytterbium codoped fiber pumped through a multimode fiber combiner. The pulses double pass the amplifier and recombine in the crystals using non-reciprocal polarization 90° rotation by a Faraday rotating mirror. Pulses with a duration of 144 fs are obtained after separation from the input beam using a polarizing beam splitter cube. These pulses have an average power of 1.85 W at a repetition rate of 80 MHz. The generation of femtosecond pulses directly from the amplifier was enabled by a positively chirped seed pulse, normally dispersive Yttrium-Vanadate crystals, and anomalously dispersive amplifier fibers. Efficient frequency doubling to 780 nm with an average power of 725 mW and a pulse duration of 156 fs is demonstrated. In summary we show a DPA setup that enables the generation of femtosecond pulses at watt-level at 1560 nm without the need for further external dechirping and demonstrate a good pulse quality by efficient frequency doubling. Due to the use of PM fiber components and a Faraday rotator the setup is environmentally stable.

Stresses in Circular Plates with Rigid Elements

Science.gov (United States)

Velikanov, N. L.; Koryagin, S. I.; Sharkov, O. V.

2018-05-01

Calculations of residual stress fields are carried out by numerical and static methods, using the flat cross-section hypothesis. The failure of metal when exposed to residual stresses is, in most cases, brittle. The presence in the engineering structures of rigid elements often leads to the crack initiation and structure failure. This is due to the fact that rigid elements under the influence of external stresses are stress concentrators. In addition, if these elements are fixed by welding, the residual welding stresses can lead to an increase in stress concentration and, ultimately, to failure. The development of design schemes for such structures is a very urgent task for complex technical systems. To determine the stresses in a circular plate with a welded circular rigid insert under the influence of an external load, one can use the solution of the plane stress problem for annular plates in polar coordinates. The polar coordinates of the points are the polar radius and the polar angle, and the stress state is determined by normal radial stresses, tangential and shearing stresses. The use of the above mentioned design schemes, formulas, will allow more accurate determination of residual stresses in annular welded structures. This will help to establish the most likely directions of failure and take measures at the stages of designing, manufacturing and repairing engineering structures to prevent these failures. However, it must be taken into account that the external load, the presence of insulation can lead to a change in the residual stress field.

Nuclear spin circular dichroism

International Nuclear Information System (INIS)

Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

2014-01-01

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra

Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

Energy Technology Data Exchange (ETDEWEB)

Huang, H.; Zhou, Y., E-mail: nzhou@uwaterloo.ca [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Duley, W. W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2015-12-14

Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

Angular distribution coefficients for γ-ray polarization produced in polarized capture reactions

International Nuclear Information System (INIS)

Wulf, E.A.; Guillemette, J.; Weller, H.R.; Seyler, R.G.

1999-01-01

The previous publications have dealt with the angular momentum formalism of both linear and circularly polarized photons in (γ, x) reactions on both polarized and unpolarized targets, and the inverse (capture) reactions initiated by polarized beams. In the present work, utilizing the general formalism of Welton, the authors deal with the linear polarization of the γ-rays which are produced in capture reactions on unpolarized targets, including the possibility of having incident polarized spin 1/2 projectiles. These capture reactions are denoted by a(rvec x, rvec L)c, where rvec x is the incident polarized spin 1/2 projectile and rvec L represents the outgoing polarized γ-ray. They present here the formalism in a convenient form, display a sample table of coefficients, and illustrate its use by means of several examples. A FORTRAN code will be made available for generating similar coefficients for other reactions

Scaling of the L2,3 circular magnetic x-ray dichroism of Fe nitrides

International Nuclear Information System (INIS)

Alouani, M.; Wills, J.M.; Wilkins, J.W.

1998-01-01

We have implemented the calculation of the x-ray-absorption cross section for left- and right-circularly polarized x-ray beams within the local-density approximation by means of our all-electron full-relativistic and spin-polarized full-potential linear muffin-tin orbital method. We show that the L 2,3 circular magnetic x-ray dichroism of Fe, Fe 3 N, and Fe 4 N compounds scales to a single curve when divided by the local magnetic moment. Sum rules determine the spin and orbital magnetic moment of iron atoms in these ordered iron nitrides. copyright 1998 The American Physical Society

CPW-fed Circularly Polarized Slot Antenna with Small Gap and Stick-shaped Shorted Strip for UHF FRID Readers

Science.gov (United States)

Pan, Chien-Yuan; Su, Chum-Chieh; Yang, Wei-Lin

2018-04-01

A new circularly polarized (CP) slot antenna with a small gap and a stick-shaped shorted strip is presented. The proposed antenna has a sufficient bandwidth for ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna structure consists of a rectangular slot with a small gap, a stick-shaped shorted strip and a 50 Ω coplanar waveguide (CPW) feedline with an asymmetrical ground plane. By using the stick -shaped shorted strip to disturb magnetic current distribution on the slot, the CP radiation can be generated. The measured results demonstrate that the proposed antenna can reach a 10 dB return loss impedance bandwidth of 14.1 % (894-1030 MHz) and a 3 dB axial ratio (AR) bandwidth of 6.4 % (910-970 MHz). The whole antenna size is 80 × 80 × 1.6 mm3.

Measuring fluorescence polarization with a dichrometer.

Science.gov (United States)

Sutherland, John C

2017-09-01

A method for obtaining fluorescence polarization data from an instrument designed to measure circular and linear dichroism is compared with a previously reported approach. The new method places a polarizer between the sample and a detector mounted perpendicular to the direction of the incident beam and results in determination of the fluorescence polarization ratio, whereas the previous method does not use a polarizer and yields the fluorescence anisotropy. A similar analysis with the detector located axially with the excitation beam demonstrates that there is no frequency modulated signal due to fluorescence polarization in the absence of a polarizer. Copyright © 2017. Published by Elsevier Inc.

NEAR-INFRARED CIRCULAR AND LINEAR POLARIMETRY OF MONOCEROS R2

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jungmi; Tamura, Motohide [Department of Astronomy, Graduate School of Science, The University of Tokyo, 113-0033 (Japan); Hough, James H. [University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Nagata, Tetsuya [Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Kusakabe, Nobuhiko [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2016-09-01

We have conducted simultaneous JHK{sub s}-band imaging circular and linear polarimetry of the Monoceros R2 (Mon R2) cluster. We present results from deep and wide near-infrared linear polarimetry of the Mon R2 region. Prominent and extended polarized nebulosities over the Mon R2 field are revisited, and an infrared reflection nebula associated with the Mon R2 cluster and two local reflection nebulae, vdB 67 and vdB 69, is detected. We also present results from deep imaging circular polarimetry in the same region. For the first time, the observations show relatively high degrees of circular polarization (CP) in Mon R2, with as much as approximately 10% in the K{sub s} band. The maximum CP extent of a ring-like nebula around the Mon R2 cluster is approximately 0.60 pc, while that of a western nebula, around vdB 67, is approximately 0.24 pc. The extended size of the CP is larger than those seen in the Orion region around IRc2, while the maximum degree of CP of ∼10% is smaller than those of ∼17% seen in the Orion region. Nonetheless, both the CP size and degree of this region are among the largest in our infrared CP survey of star-forming regions. We have also investigated the time variability of the degree of the polarization of several infrared sources and found possible variations in three sources.

Measurement of neutron spectra for photonuclear reaction with linearly polarized photons

Directory of Open Access Journals (Sweden)

Kirihara Yoichi

2017-01-01

Full Text Available Spectra of neutrons produced by a photonuclear reaction from a 197Au target were measured using 16.95 MeV linearly and circularly polarized photon beams at NewSUBARU-BL01 using a time-of-flight method. The difference in the neutron spectra between the cases of a linearly and circularly polarized photon was measured. The difference in the neutron yield increased with the neutron energy and was approximately threefold at the maximum neutron energy. In a direction perpendicular to that of the linear polarization, the neutron yields decreased as the neutron energy increased.

Three-dimensional polarization states of monochromatic light fields.

Science.gov (United States)

Azzam, R M A

2011-11-01

The 3×1 generalized Jones vectors (GJVs) [E(x) E(y) E(z)](t) (t indicates the transpose) that describe the linear, circular, and elliptical polarization states of an arbitrary three-dimensional (3-D) monochromatic light field are determined in terms of the geometrical parameters of the 3-D vibration of the time-harmonic electric field. In three dimensions, there are as many distinct linear polarization states as there are points on the surface of a hemisphere, and the number of distinct 3-D circular polarization states equals that of all two-dimensional (2-D) polarization states on the Poincaré sphere, of which only two are circular states. The subset of 3-D polarization states that results from the superposition of three mutually orthogonal x, y, and z field components of equal amplitude is considered as a function of their relative phases. Interesting contours of equal ellipticity and equal inclination of the normal to the polarization ellipse with respect to the x axis are obtained in 2-D phase space. Finally, the 3×3 generalized Jones calculus, in which elastic scattering (e.g., by a nano-object in the near field) is characterized by the 3-D linear transformation E(s)=T E(i), is briefly introduced. In such a matrix transformation, E(i) and E(s) are the 3×1 GJVs of the incident and scattered waves and T is the 3×3 generalized Jones matrix of the scatterer at a given frequency and for given directions of incidence and scattering.

Selective Deflection of Polarized Light Via Coherently Driven Four-Level Atoms in a Double-Λ Configuration

International Nuclear Information System (INIS)

Guo Yu

2010-01-01

We study the interaction of a weak probe field, having two circular polarized components, i.e., σ - and σ + polarization, with an optically dense medium of four-level atoms in a double-Λ configuration, which is mediated by the electromagnetically induced transparency with a polarized control light with spatially inhomogeneous profile. We analyse the deflection of the polarized probe light and we find that we can selectively determine which circular component will be deflected after the polarized probe light enters the atom medium via adjusting the polarization and detuning of the control field. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Traveling wave deflector design for femtosecond streak camera

International Nuclear Information System (INIS)

Pei, Chengquan; Wu, Shengli; Luo, Duan; Wen, Wenlong; Xu, Junkai; Tian, Jinshou; Zhang, Minrui; Chen, Pin; Chen, Jianzhong; Liu, Rong

2017-01-01

In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.

Traveling wave deflector design for femtosecond streak camera

Energy Technology Data Exchange (ETDEWEB)

Pei, Chengquan; Wu, Shengli [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Luo, Duan [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wen, Wenlong [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Xu, Junkai [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tian, Jinshou, E-mail: tianjs@opt.ac.cn [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Zhang, Minrui; Chen, Pin [Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi' an 710119 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Jianzhong [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi' an Jiaotong University, Xi’an 710049 (China); Liu, Rong [Xi' an Technological University, Xi' an 710021 (China)

2017-05-21

In this paper, a traveling wave deflection deflector (TWD) with a slow-wave property induced by a microstrip transmission line is proposed for femtosecond streak cameras. The pass width and dispersion properties were simulated. In addition, the dynamic temporal resolution of the femtosecond camera was simulated by CST software. The results showed that with the proposed TWD a femtosecond streak camera can achieve a dynamic temporal resolution of less than 600 fs. Experiments were done to test the femtosecond streak camera, and an 800 fs dynamic temporal resolution was obtained. Guidance is provided for optimizing a femtosecond streak camera to obtain higher temporal resolution.

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

Science.gov (United States)

2014-12-08

1995). 42. Eichmann , H. et al. Polarization-dependent high-order two-color mixing. Phys. Rev. A 51, R3414–R3417 (1995). 43. Fleischer, A., Kfir, O...calculations of polarization-dependent two- color high-harmonic generation. Phys. Rev. A 52, 2262–2278 (1995). 10. Eichmann , H. et al. polarization

Electron's anomalous magnetic-moment effects on electron-hydrogen elastic collisions in the presence of a circularly polarized laser field

International Nuclear Information System (INIS)

Elhandi, S.; Taj, S.; Attaourti, Y.; Manaut, B.; Oufni, L.

2010-01-01

The effect of the electron's anomalous magnetic moment on the relativistic electronic dressing for the process of electron-hydrogen atom elastic collisions is investigated. We consider a laser field with circular polarization and various electric field strengths. The Dirac-Volkov states taking into account this anomaly are used to describe the process in the first order of perturbation theory. The correlation between the terms coming from this anomaly and the electric field strength gives rise to the strong dependence of the spinor part of the differential cross section (DCS) with respect to these terms. A detailed study has been devoted to the nonrelativistic regime as well as the moderate relativistic regime. Some aspects of this dependence as well as the dynamical behavior of the DCS in the relativistic regime have been addressed.

Local Polar Fluctuations in Lead Halide Perovskite Crystals

Science.gov (United States)

Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

2017-03-01

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3 NH3 PbBr3 ) and all-inorganic (CsPbBr3 ) lead-halide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-to-head Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3 .

Local Polar Fluctuations in Lead Halide Perovskite Crystals

Energy Technology Data Exchange (ETDEWEB)

Yaffe, Omer; Guo, Yinsheng; Tan, Liang Z.; Egger, David A.; Hull, Trevor; Stoumpos, Constantinos C.; Zheng, Fan; Heinz, Tony F.; Kronik, Leeor; Kanatzidis, Mercouri G.; Owen, Jonathan S.; Rappe, Andrew M.; Pimenta, Marcos A.; Brus, Louis E.

2017-03-01

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations that inhibit carrier recombination. We combine low-frequency Raman scattering with first-principles molecular dynamics (MD) to study the fundamental nature of these local polar fluctuations. Our observations of a strong central peak in the cubic phase of both hybrid (CH3NH3PbBr3) and all-inorganic (CsPbBr3) leadhalide perovskites show that anharmonic, local polar fluctuations are intrinsic to the general lead-halide perovskite structure, and not unique to the dipolar organic cation. MD simulations indicate that head-tohead Cs motion coupled to Br face expansion, occurring on a few hundred femtosecond time scale, drives the local polar fluctuations in CsPbBr3.

Femtosecond lasers for countermeasure applications

NARCIS (Netherlands)

Franssen, G.C.; Schleijpen, H.M.A.; Heuvel, J.C. van den; Buersing, H.; Eberle, B.; Walter, D.

2009-01-01

In recent years, much advance in the field of high-power femtosecond laser technology has been made. The high pulse power of femtosecond laser systems leads to various interesting phenomena, such as a very high power density and the formation of a plasma in the propagation medium, which is usually

Formation of organic layer on femtosecond laser-induced periodic surface structures

Energy Technology Data Exchange (ETDEWEB)

Yasumaru, Naoki, E-mail: yasuma@fukui-nct.ac.jp [National Institute of Technology, Fukui College, Sabae, Fukui 916-8507 (Japan); Sentoku, Eisuke [National Institute of Technology, Fukui College, Sabae, Fukui 916-8507 (Japan); Kiuchi, Junsuke [Eyetec Co., Ltd., Sabae, Fukui 916-0016 (Japan)

2017-05-31

Highlights: • Surface analyses of two types of femtosecond laser-induced periodic surface structures (LIPSS) on titanium were conducted. • The parallel-oriented ultrafine LIPSS showed the almost same roughness and chemical states as the non-irradiated Ti surface. • The well-known perpendicular-oriented LIPSS were typically covered with an organic layer similar to a cellulose derivative. - Abstract: Two types of laser-induced periodic surface structures (LIPSS) formed on titanium by femtosecond (fs) laser pulses (λ = 800 nm, τ = 180 fs, ν = 1 kHz) in air were investigated experimentally. At a laser fluence F above the ablation threshold, LIPSS with a minimum mean spacing of D < λ⁄2 were observed perpendicular to the laser polarization direction. In contrast, for F slightly below than the ablation threshold, ultrafine LIPSS with a minimum value of D < λ/10 were formed parallel to the polarization direction. The surface roughness of the parallel-oriented LIPSS was almost the same as that of the non-irradiated surface, unlike the high roughness of the perpendicular-oriented LIPSS. In addition, although the surface state of the parallel-oriented LIPSS was the same as that of the non-irradiated surface, the perpendicular-oriented LIPSS were covered with an organic thin film similar to a cellulose derivative that cannot be easily formed by conventional chemical synthesis. The results of these surface analyses indicate that these two types of LIPSS are formed through different mechanisms. This fs-laser processing technique may become a new technology for the artificial synthesis of cellulose derivatives.

Visualization of femtosecond laser-induced stress anisotropy in amorphous and crystalline materials

Directory of Open Access Journals (Sweden)

McMillen Ben

2015-01-01

Full Text Available In recent years, micro manufacturing with femtosecond lasers has received considerable attention as an efficient technique for producing three-dimensional devices, combining multiple functionalities in a single monolithic substrate. In this manufacturing process, stress-anisotropy resulting from non-ablative laser exposure can have both positive and negative effects on the process out-come. In this work, we present a simple method for visualizing stress anisotropy, combining highly symmetric laser-written patterns with polarization microscopy, as a tool for identifying the various anisotropic contributions to the laser fabrication process.

Experimentally determined characteristics of the degree of polarization of backscattered light from polystyrene sphere suspensions

International Nuclear Information System (INIS)

Sun, Ping; Ma, Yongchao; Xu, Chengwei; Sun, Xiaochun; Liu, Wei

2013-01-01

The degree of polarization (DOP) can be used to characterize the polarization-maintaining ability of a beam of polarized light propagating through a turbid medium. Experiments on polystyrene (PST) sphere suspensions show that, the linearly polarized light propagating through the PST sphere suspension of Rayleigh scatterers has better polarization-maintaining ability, whereas the circularly polarized light propagating through the PST sphere suspension of Mie scatterers has better polarization-maintaining ability. Moreover, helicity flipping occurs to the circularly polarized light propagating in the extremely weak PST sphere suspensions or on the surface of suspensions. In addition, the DOP is dependent on the wavelength of incident light. The results can be helpful to image in turbid media by use of diffuse backscattered light. (paper)

Calculated Performance Of The Variable-Polarization Undulator Upgrade To The Daresbury SRS Soft X-Ray Undulator Beamline

International Nuclear Information System (INIS)

Roper, Mark D.; Bird, Daniel T.

2004-01-01

The soft x-ray beamline 5U1 on the Daresbury Laboratory SRS currently uses a planar undulator, producing linearly polarized radiation in the range 100 to 1000 eV. The undulator is soon to be replaced by a variable-polarization device of the Apple II design. The aim is to produce circularly polarized light in the energy range 265 to 1000 eV, covering the K-edges of C, N and O, and the first row transition element L-edges. This will greatly enhance the provision of circularly polarized soft-x-rays on the SRS and open up new opportunities for experimenters. The device will also produce linear polarization with a selectable angle of polarization with respect to the orbit plane, which is currently unavailable on the SRS. In order to provide the coverage over this energy range, we are exploiting the relatively large emittance of the SRS to allow us to use the second and third harmonics even in circular polarization mode. This paper presents the expected beamline output in various polarization modes and the predicted degree of polarization

Enhancement of Chiroptical Signals by Circular Differential Mie Scattering of Nanoparticles

OpenAIRE

SeokJae Yoo; Q-Han Park

2015-01-01

We enhance the weak optical signals of small chiral molecules via circular differential Mie scattering (CDMS) of nanoparticles immersed in them. CDMS is the preferential Mie scattering of left- and right-handed circularly polarized light by nanoparticles whose sizes are about the same as the wavelength of light. Solving the Mie scattering theory for chiral media, we find that the CDMS signal of the particle is linearly proportional to the chirality parameter κ of the molecules. This linear am...

Circularly polarized triple band glass shaped monopole patch antenna with metallic reflector for bluetooth & wireless applications

Energy Technology Data Exchange (ETDEWEB)

Jangid, K. G.; Kulhar, V. S. [Department of Physics, Manipal University Jaipur, Jaipur-303007 (India); Choudhary, N.; Jain, P.; Sharma, B. R.; Saini, J. S.; Bhatnagar, D., E-mail: dbhatnagar-2000@rediffmail.com [Microwave Lab, Department of Physics, University of Rajasthan, Jaipur-302004 (India)

2016-03-09

This paper presents the design and performance of strip line fed glass shaped monopole patch antenna having with overall size 30mm × 30 mm × 1.59 mm. In the patch; an eight shaped slot and in the ground plane an eight shaped ring are introduced. A metallic ground plane is also introduced at appropriate location beneath the ground plane. The proposed antenna is simulated by applying CST Microwave Studio simulator. Antenna provides circularly polarized radiations, triple broad impedance bandwidth of 203MHz (2.306GHz to 2.510GHz), 42MHz (2.685GHz to 2.757GHz) & GHz (3.63 GHz to 6.05 GHz), high flat gain (close to 5dBi) and good radiation properties in the desired frequency range. This antenna may be a very useful tool for 2.45GHz Bluetooth communication band as well as for 2.4GHz/5.2 GHz /5.8 GHz WLAN bands & 3.7GHz/5.5 GHz Wi-Max bands.

Electron dynamics and optical properties modulation of monolayer MoS{sub 2} by femtosecond laser pulse: a simulation using time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Su, Xiaoxing; Jiang, Lan [Beijing Institute of Technology, Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing (China); Wang, Feng [Beijing Institute of Technology, School of Physics, Beijing (China); Su, Gaoshi [Beijing Institute of Technology, School of Mechatronical Engineering, Beijing (China); Qu, Liangti [Beijing Institute of Technology, Key Laboratory of Cluster Science, Ministry of Education, School of Chemistry, Beijing (China); Lu, Yongfeng [University of Nebraska-Lincoln, Department of Electrical Engineering, Lincoln, NE (United States)

2017-07-15

In this study, we adopted time-dependent density functional theory to investigate the optical properties of monolayer MoS{sub 2} and the effect of intense few-cycle femtosecond laser pulses on these properties. The electron dynamics of monolayer MoS{sub 2} under few-cycle and multi-cycle laser irradiation were described. The polarization direction of the laser had a marked effect on the energy absorption and electronic excitation of monolayer MoS{sub 2} because of anisotropy. Change in the polarization direction of few-cycle pulse changed the absorbed energy by a factor over 4000. Few-cycle pulse showed a higher sensitivity to the electronic property of material than multi-cycle pulse. The modulation of the dielectric properties of the material was observed on the femtosecond time scale. The negative divergence appeared in the real part of the function at low frequencies and photoinduced blue shift occurred due to Burstein-Moss effect. The irradiation of femtosecond laser caused the dielectric response within the infrared region and introduced anisotropy to the in-plane optical properties. Laser-based engineering of optical properties through controlling transient electron dynamics expands the functionality of MoS{sub 2} and has potential applications in direction-dependent optoelectronic devices. (orig.)

Polarized Proton Collisions at RHIC

CERN Document Server

Bai, Mei; Alekseev, Igor G; Alessi, James; Beebe-Wang, Joanne; Blaskiewicz, Michael; Bravar, Alessandro; Brennan, Joseph M; Bruno, Donald; Bunce, Gerry; Butler, John J; Cameron, Peter; Connolly, Roger; De Long, Joseph; Drees, Angelika; Fischer, Wolfram; Ganetis, George; Gardner, Chris J; Glenn, Joseph; Hayes, Thomas; Hseuh Hsiao Chaun; Huang, Haixin; Ingrassia, Peter; Iriso, Ubaldo; Laster, Jonathan S; Lee, Roger C; Luccio, Alfredo U; Luo, Yun; MacKay, William W; Makdisi, Yousef; Marr, Gregory J; Marusic, Al; McIntyre, Gary; Michnoff, Robert; Montag, Christoph; Morris, John; Nicoletti, Tony; Oddo, Peter; Oerter, Brian; Osamu, Jinnouchi; Pilat, Fulvia Caterina; Ptitsyn, Vadim; Roser, Thomas; Satogata, Todd; Smith, Kevin T; Svirida, Dima; Tepikian, Steven; Tomas, Rogelio; Trbojevic, Dejan; Tsoupas, Nicholaos; Tuozzolo, Joseph; Vetter, Kurt; Wilinski, Michelle; Zaltsman, Alex; Zelenski, Anatoli; Zeno, Keith; Zhang, S Y

2005-01-01

The Relativistic Heavy Ion Collider~(RHIC) provides not only collisions of ions but also collisions of polarized protons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin depolarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC to avoid depolarizing resonances. In 2003, polarized proton beams were accelerated to 100~GeV and collided in RHIC. Beams were brought into collisions with longitudinal polarization at the experiments STAR and PHENIX by using spin rotators. RHIC polarized proton run experience demonstrates that optimizing polarization transmission efficiency and improving luminosity performance are significant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity production in beam-beam limite...

Femtosecond lasers for microsurgery of cornea

International Nuclear Information System (INIS)

Vartapetov, Sergei K; Khudyakov, D V; Lapshin, Konstantin E; Obidin, Aleksei Z; Shcherbakov, Ivan A

2012-01-01

The review of femtosecond laser installations for medical applications is given and a new femtosecond ophthalmologic system for creation of a flap of corneal tissue during the LASIK operation is described. An all-fibre femtosecond laser emitting ∼400-fs pulses at 1067 nm is used. The pulse repetition rate can vary from 200 kHz up to 1 MHz. The output energy of the femtosecond system does not exceed 1 μJ. A specially developed objective with small spherical and chromatic aberrations is applied to focus laser radiation to an area of an eye cornea. The size of the focusing spot does not exceed 3 μm. To process the required area, scanning by a laser beam is applied with a speed no less than 5 m s -1 . At a stage of preliminary tests of the system, the Κ8 glass, organic PMMA glass and specially prepared agarose gels are used as a phantom of an eye. The femtosecond system is successfully clinically tested on a plenty of eyes of a pig and on several human eyes. The duration of the procedure of creation of a corneal flap does not exceed 20 s.

Femtosecond lasers for microsurgery of cornea

Energy Technology Data Exchange (ETDEWEB)

Vartapetov, Sergei K; Khudyakov, D V; Lapshin, Konstantin E; Obidin, Aleksei Z; Shcherbakov, Ivan A

2012-03-31

The review of femtosecond laser installations for medical applications is given and a new femtosecond ophthalmologic system for creation of a flap of corneal tissue during the LASIK operation is described. An all-fibre femtosecond laser emitting {approx}400-fs pulses at 1067 nm is used. The pulse repetition rate can vary from 200 kHz up to 1 MHz. The output energy of the femtosecond system does not exceed 1 {mu}J. A specially developed objective with small spherical and chromatic aberrations is applied to focus laser radiation to an area of an eye cornea. The size of the focusing spot does not exceed 3 {mu}m. To process the required area, scanning by a laser beam is applied with a speed no less than 5 m s{sup -1}. At a stage of preliminary tests of the system, the {Kappa}8 glass, organic PMMA glass and specially prepared agarose gels are used as a phantom of an eye. The femtosecond system is successfully clinically tested on a plenty of eyes of a pig and on several human eyes. The duration of the procedure of creation of a corneal flap does not exceed 20 s.

Spin dynamics of electron beams in circular accelerators

International Nuclear Information System (INIS)

Boldt, Oliver

2014-04-01

Experiments using high energy beams of spin polarized, charged particles still prove to be very helpful in disclosing a deeper understanding of the fundamental structure of matter. An important aspect is to control the beam properties, such as brilliance, intensity, energy, and degree of spin polarization. In this context, the present studies show various numerical calculations of the spin dynamics of high energy electron beams in circular accelerators. Special attention has to be paid to the emission of synchrotron radiation, that occurs when deflecting charged particles on circular orbits. In the presence of the fluctuation of the kinetic energy due to the photon emission, each electron spin moves non-deterministically. This stochastic effect commonly slows down the speed of all numeric estimations. However, the shown simulations cover - using appropriate approximations - trackings for the motion of thousands of electron spins for up to thousands of turns. Those calculations are validated and complemented by empirical investigations at the electron stretcher facility ELSA of the University of Bonn. They can largely be extended to other boundary conditions and thus, can be consulted for new accelerator layouts.

Detailed analysis of evolution of the state of polarization in all-fiber polarization transformers.

Science.gov (United States)

Zhu, Xiushan; Jain, Ravinder K

2006-10-30

We present a detailed analysis of key attributes and performance characteristics of controllably-spun birefringent-fiber-based all-fiber waveplates or "all fiber polarization transformers" (AFPTs), first proposed and demonstrated by Huang [11]; these AFPTs consist essentially of a long carefully-designed "spin-twisted" high-birefringence fiber, fabricated by slowly varying the spin rate of a birefringent fiber preform (either from very fast to very slow or vice versa) while the fiber is being drawn. The evolution of the eigenstate from a linear polarization state to a circular polarization state, induced by slow variation of the intrinsic structure from linear anisotropy at the unspun end to circular anisotropy at the fast-spun end, enables the AFPT to behave like an all-fiber quarter-wave plate independent of the wavelength of operation. Power coupling between local eigenstates causes unique evolution of the polarization state along the fiber, and has been studied to gain insight into - as well as to understand detailed characteristics of -- the polarization transformation behavior. This has been graphically illustrated via plots of the relative power in these local eigenstates as a function of distance along the length of the fiber and plots of the extinction ratio of the output state of polarization (SOP) as a function of distance and the normalized spin rate. Deeper understanding of such polarization transformers has been further elucidated by quantitative calculations related to two crucial requirements for fabricating practical AFPT devices. Our calculations have also indicated that the polarization mode dispersion behaviour of the AFPT is much smaller than that of the original birefringent fiber. Finally, a specific AFPT was experimentally investigated at two widely-separated wavelengths (1310 nm and 1550 nm) of interest in telecommunications systems applications, further demonstrating and elucidating the broadband character of such AFPTs.

Imaging differential polarization microscope with electronic readout

International Nuclear Information System (INIS)

Mickols, W.; Tinoco, I.; Katz, J.E.; Maestre, M.F.; Bustamante, C.

1985-01-01

A differential polarization microscope forms two images: one of the transmitted intensity and the other due to the change in intensity between images formed when different polarizations of light are used. The interpretation of these images for linear dichroism and circular dichroism are described. The design constraints on the data acquisition systems and the polarization modulation are described. The advantage of imaging several biological systems which contain optically anisotropic structures are described

Diffraction from polarization holographic gratings with surface relief in side-chain azobenzene polyesters

DEFF Research Database (Denmark)

Naydenova, I; Nikolova, L; Todorov, T

1998-01-01

We investigate the polarization properties of holographic gratings in side-chain azobenzene polyesters in which an anisotropic grating that is due to photoinduced linear and circular birefringence is recorded in the volume of the material and a relief grating appears on the surface. A theoretical...... model is proposed to explain the experimental results, making it possible to understand the influence of the different photoinduced effects. It is shown that at low intensity the polarization properties of the diffraction at these gratings are determined by the interaction of the linear and circular...... photobirefringences, and at larger intensity the influence of the surface relief dominates the effect of the circular anisotropy. Owing to the high recording efficiency of the polyesters, the +/-1-order diffracted waves change the polarization interference pattern during the holographic recording, resulting...

Modeling magnetic circular dichroism within the polarizable embedding approach

DEFF Research Database (Denmark)

Nørby, Morten Steen; Coriani, Sonia; Kongsted, Jacob

2018-01-01

Magnetic circular dichroism (MCD) is defined as the differential absorption of left and right circularly polarized light in a sample subjected to an external magnetic field. In order to interpret the results of MCD measurements, theoretical predictions of key MCD parameters can be of utmost...... importance. From an experimental point of view, MCD spectra of molecules are often measured in an environment and most notably in a solution. Thus, it may be very important that the method used to predict the MCD parameters is able to correctly account for medium effects. In this paper, we investigate...

Broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface

Science.gov (United States)

Mao, Chenyang; Yang, Yang; He, Xiaoxiang; Zheng, Jingming; Zhou, Chun

2017-12-01

In this paper, a broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface is proposed. The proposed metasurface can effectively convert linear-polarized (TE/TM) incident wave into the reflected wave with three different polarizations within the frequency bands of 5.5-22.75 GHz. Based on the electric and magnetic resonant features of the double-L-shaped structure, the proposed metasurface can convert linearly polarized waves into cross-polarized waves at three resonant frequency bands. Furthermore, the incident linearly polarized waves can be effectively converted into left/right handed circular-polarized (LHCP and RHCP) waves at other four non-resonance frequency bands. Thus, the proposed metasurface can be regarded as a seven-band multi-polarization converter. The prototype of the proposed polarization converter is analyzed and measured. Both simulated and measured results show the 3-dB axis ratio bandwidth of circular polarization bands and the high polarization conversion efficiency of cross-polarization bands when the incident wave changes from 0° to 30° at both TE and TM modes.

Circular dichroism in a three-dimensional semiconductor chiral photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Takahashi, S.; Ota, Y.; Tatebayashi, J. [Institute of Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Tajiri, T. [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Iwamoto, S.; Arakawa, Y. [Institute of Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

2014-08-04

Circular dichroism covering the telecommunication band is experimentally demonstrated in a semiconductor-based three-dimensional chiral photonic crystal (PhC). We design a rotationally stacked woodpile PhC structure where neighboring layers are rotated by 60° and three layers construct a single helical unit. The mirror-asymmetric PhC made from GaAs with sub-micron periodicity is fabricated by a micro-manipulation technique. Due to the large contrast of refractive indices between GaAs and air, the experimentally obtained circular dichroism extends over a wide wavelength range, with the transmittance of right-handed circularly polarized incident light being 85% and that of left-handed light being 15% at a wavelength of 1.3 μm. The obtained results show good agreement with numerical simulations.

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells studied by transient circular dichromatic absorption spectroscopy at room temperature.

Science.gov (United States)

Fang, Shaoyin; Zhu, Ruidan; Lai, Tianshu

2017-03-21

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells is studied using time-resolved circular dichromatic absorption spectroscopy at room temperature. It is found that ultrafast dynamics is dominated by the cooperative contributions of band filling and many-body effects. The relative contribution of the two effects is opposite in strength for electrons and holes. As a result, transient circular dichromatic differential transmission (TCD-DT) with co- and cross-circularly polarized pump and probe presents different strength at several picosecond delay time. Ultrafast spin relaxation dynamics of excited holes is sensitively reflected in TCD-DT with cross-circularly polarized pump and probe. A model, including coherent artifact, thermalization of nonthermal carriers and the cooperative contribution of band filling and many-body effects, is developed, and used to fit TCD-DT with cross-circularly polarized pump and probe. Spin relaxation time of holes is achieved as a function of excited hole density for the first time at room temperature, and increases with hole density, which disagrees with a theoretical prediction based on EY spin relaxation mechanism, implying that EY mechanism may be not dominant hole spin relaxation mechanism at room temperature, but DP mechanism is dominant possibly.

Interferometric polarization control

International Nuclear Information System (INIS)

Chuss, David T.; Wollack, Edward J.; Moseley, S. Harvey; Novak, Giles

2006-01-01

We develop the Jones and Mueller matrices for structures that allow control of the path length difference between two linear orthogonal polarizations and consider the effect of placing multiple devices in series. Specifically, we find that full polarization modulation (measurement of Stokes Q, U, and V) can be achieved by placing two such modulators in series if the relative angles of the beam-splitting grids with respect to the analyzer orientation are appropriately chosen. Such a device has several potential advantages over a spinning wave plate modulator for measuring astronomical polarization in the far infrared through millimeter: (i) The use of small, linear motions eliminates the need for cryogenic rotational bearings; (ii) the phase flexibility allows measurement of circular as well as linear polarization; and (iii) this architecture allows for both multiwavelength and broadband modulation. We also present initial laboratory results

Electrically tunable polarizer based on 2D orthorhombic ferrovalley materials

Science.gov (United States)

Shen, Xin-Wei; Tong, Wen-Yi; Gong, Shi-Jing; Duan, Chun-Gang

2018-03-01

The concept of ferrovalley materials has been proposed very recently. The existence of spontaneous valley polarization, resulting from ferromagnetism, in such hexagonal 2D materials makes nonvolatile valleytronic applications realizable. Here, we introduce a new member of ferrovalley family with orthorhombic lattice, i.e. monolayer group-IV monochalcogenides (GIVMs), in which the intrinsic valley polarization originates from ferroelectricity, instead of ferromagnetism. Combining the group theory analysis and first-principles calculations, we demonstrate that, different from the valley-selective circular dichroism in hexagonal lattice, linearly polarized optical selectivity for valleys exists in the new type of ferrovalley materials. On account of the distinctive property, a prototype of electrically tunable polarizer is realized. In the ferrovalley-based polarizer, a laser beam can be optionally polarized in x- or y-direction, depending on the ferrovalley state controlled by external electric fields. Such a device can be further optimized to emit circularly polarized radiation with specific chirality and to realize the tunability for operating wavelength. Therefore, we show that 2D orthorhombic ferrovalley materials are the promising candidates to provide an advantageous platform to realize the polarizer driven by electric means, which is of great importance in extending the practical applications of valleytronics.

Detecting chameleons: The astronomical polarization produced by chameleonlike scalar fields

International Nuclear Information System (INIS)

Burrage, Clare; Davis, Anne-Christine; Shaw, Douglas J.

2009-01-01

We show that a coupling between chameleonlike scalar fields and photons induces linear and circular polarization in the light from astrophysical sources. In this context chameleonlike scalar fields include those of the Olive-Pospelov (OP) model, which describes a varying fine structure constant. We determine the form of this polarization numerically and give analytic expressions in two useful limits. By comparing the predicted signal with current observations we are able to improve the constraints on the chameleon-photon coupling and the coupling in the OP model by over 2 orders of magnitude. It is argued that, if observed, the distinctive form of the chameleon induced circular polarization would represent a smoking gun for the presence of a chameleon. We also report a tentative statistical detection of a chameleonlike scalar field from observations of starlight polarization in our galaxy.

Optical reconfiguration and polarization control in semi-continuous gold films close to the percolation threshold

DEFF Research Database (Denmark)

Frydendahl, Christian; Repän, Taavi; Geisler, Mathias

2017-01-01

permanent morphological changes with a femtosecond (fs)-pulsed laser above a critical power. Optical transmission spectroscopy measurements show a correlation between the spectra of the morphologically modified films and the wavelength, polarization, and the intensity of the laser used for alteration...

Recent advances in femtosecond laser-assisted cataract surgery

Directory of Open Access Journals (Sweden)

Zhao-Jie Chu

2013-07-01

Full Text Available Perfect vision and fewer complications is our goal in cataract surgery, femtosecond laser-assisted cataract surgery hold the promise. Applications of femtosecond laser technology for capsulotomy, nuclear fragmentation and corneal incision in cataract surgery bring a new level of accuracy, reproducibility and predictability over the current cataract surgery. The femtosecond laser produces capsulotomies that are more precise, accurate, reproducible, and stronger than those created with the conventional manual technique, and further helps maintain proper positioning of the IOL. Femtosecond laser in nuclear fragmentation lead to a lower effective phacoemulsification time, and the corneal incision is more stable. But currently there are some complications and a clear learning curve associated with the use of femtosecond lasers for cataract surgery. The long-term safety and visual outcomes still need further investigation.

Micromachining of semiconductor by femtosecond laser for integrated circuit defect analysis

Energy Technology Data Exchange (ETDEWEB)

Halbwax, M. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France); Sarnet, T. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France)], E-mail: sarnet@lp3.univ-mrs.fr; Hermann, J.; Delaporte, Ph.; Sentis, M. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France); Fares, L.; Haller, G. [STMicroelectronics, 190 Avenue Celestin Coq, ZI, 13106 Rousset Cedex (France)

2007-12-15

The latest International Technology Roadmap for Semiconductors (ITRS) has highlighted the detection and analysis of defects in Integrated Circuits (IC) as a major challenge faced by the semiconductor industry. Advanced tools used today for defect cross sectioning include dual beams (focused ion- and electron-beam technologies) with resolution down to the sub-Angstrom level. However ion milling an IC with a FIB is time consuming because of the need to open wide cavities in front of the cross-sections that need to be analyzed. Therefore the use of a femtosecond laser as a tool for direct material removal is discussed in this paper. Experiments were performed on IC structures to reveal the different layers of fabrication: selective or total ablation can occur depending on the laser energy density, without delamination of the layers. Different laser irradiation conditions like pressure (air, vacuum), polarization, beam shaping, and scanning parameters have been used to produce different types of cavities. The femtosecond laser engraving of silicon-based structures could be useful for cross-sectioning devices but also for other applications like direct-write lithography, photomask repair, maskless implantation or reverse engineering/restructuring.

Micromachining of semiconductor by femtosecond laser for integrated circuit defect analysis

International Nuclear Information System (INIS)

Halbwax, M.; Sarnet, T.; Hermann, J.; Delaporte, Ph.; Sentis, M.; Fares, L.; Haller, G.

2007-01-01

The latest International Technology Roadmap for Semiconductors (ITRS) has highlighted the detection and analysis of defects in Integrated Circuits (IC) as a major challenge faced by the semiconductor industry. Advanced tools used today for defect cross sectioning include dual beams (focused ion- and electron-beam technologies) with resolution down to the sub-Angstrom level. However ion milling an IC with a FIB is time consuming because of the need to open wide cavities in front of the cross-sections that need to be analyzed. Therefore the use of a femtosecond laser as a tool for direct material removal is discussed in this paper. Experiments were performed on IC structures to reveal the different layers of fabrication: selective or total ablation can occur depending on the laser energy density, without delamination of the layers. Different laser irradiation conditions like pressure (air, vacuum), polarization, beam shaping, and scanning parameters have been used to produce different types of cavities. The femtosecond laser engraving of silicon-based structures could be useful for cross-sectioning devices but also for other applications like direct-write lithography, photomask repair, maskless implantation or reverse engineering/restructuring

Laser-driven polarized H/D sources and targets

International Nuclear Information System (INIS)

Clasie, B.; Crawford, C.; Dutta, D.; Gao, H.; Seely, J.; Xu, W.

2005-01-01

Traditionally, Atomic Beam Sources are used to produce targets of nuclear polarized hydrogen (H) or deuterium (D) for experiments using storage rings. Laser-Driven Sources (LDSs) offer a factor of 20-30 gain in the target thickness (however, with lower polarization) and may produce a higher overall figure of merit. The LDS is based on the technique of spin-exchange optical pumping where alkali vapor is polarized by absorbing circularly polarized laser photons. The H or D atoms are nuclear-polarized through spin-exchange collisions with the polarized alkali vapor and through subsequent hyperfine interactions during frequent H-H or D-D collisions

Observer-dependent sign inversions of polarization singularities.

Science.gov (United States)

Freund, Isaac

2014-10-15

We describe observer-dependent sign inversions of the topological charges of vector field polarization singularities: C points (points of circular polarization), L points (points of linear polarization), and two virtually unknown singularities we call γ(C) and α(L) points. In all cases, the sign of the charge seen by an observer can change as she changes the direction from which she views the singularity. Analytic formulas are given for all C and all L point sign inversions.

High-efficiency broadband polarization converter based on Ω-shaped metasurface

Science.gov (United States)

Zhang, Tianyao; Huang, Lingling; Li, Xiaowei; Liu, Juan; Wang, Yongtian

2017-11-01

The polarization state, which cannot be directly detected by human eyes, forms an important characteristic of electromagnetic waves. Control of polarization states has long been pursued for various applications. Conventional polarization converters can hardly meet the requirements in lab-on-chip systems, due to the involvement of bulk materials. Here, we propose the design and realization of a linear to circular polarization converter based on metasurfaces. The metasurface is deliberately designed using achiral two-fold mirror symmetry Ω-shaped antennas. The converter integrates a ground metal plane, a spacer dielectric layer and an antenna array, leading to a high conversion efficiency and broad operating bandwidth in the near infrared regime. The calculated Stokes parameters indicate an excellent conversion of linear to circular polarization for the reflected light. The tunability of the bandwidth by oblique incidence and by modulating the thickness of the dielectric layer is also introduced and demonstrated, which shows great flexibilities for such metasurface converters. The proposed metasurface may open up intriguing possibilities towards the realization of ultrathin nanophotonic devices for polarization manipulation and wavefront engineering.