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Circular Polarization (circular + polarization)
Selected AbstractsPolymer Photovoltaic Cells Sensitive to the Circular Polarization of LightADVANCED MATERIALS, Issue 20 2010Jan Gilot 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 of all layers inside the device. [source] The distribution of circularly polarized light reflection in the Scarabaeoidea (Coleoptera)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010J. DAVID PYE fls The light reflected from many scarab beetles is strongly circularly polarized, a phenomenon that may be unique in nature. Approximately 1500 genera and more than 19 000 species/subspecies of scarab beetles (Scarabaeoidea) in the collection of the Natural History Museum, London, were surveyed with circularly polarizing filters to assess how widespread this effect is and how it relates to colour patterns in the individuals concerned. Over 1100 measurements were made of the strength of the circular polarization, in some cases registering 97%. Circular polarization had been previously described from five subfamilies of Scarabaeidae and, in the present study, was found in three further subfamilies: Phaenomeridinae, Dynastinae and Euchirinae, as well as in the subfamily Ceratocanthinae of the family Hybosoridae, comprising the first records outside the Scarabaeidae. The results may have implications for the taxonomy of the group, for visual discrimination, and for the behaviour of the species themselves. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 585,596. [source] Polymer Photovoltaic Cells Sensitive to the Circular Polarization of LightADVANCED MATERIALS, Issue 20 2010Jan Gilot 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 of all layers inside the device. [source] A T-type fractal boundary single-feed circularly polarized microstrip antennaINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2009P. Nageswara Rao Abstract A single-feed T-type fractal boundary microstrip antenna is presented. It is established that a very good circular polarization is realizable with 3-dB axial ratio bandwidth of 1.27% at the center frequency of 2446 MHz by changing the electrical length in two directions of the square patch by using T-type fractal curve as boundary. Further it is shown that the surface area occupied by the antenna is reduced compared to the Euclidean shaped patch antenna without much degradation in gain of the antenna. Experimental results are compared with simulated results and a very good agreement is obtained. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] GeV-acceleration of electron by a superintense ultrashort laser pulseLASER PHYSICS LETTERS, Issue 8 2004A. Bahari Abstract New mechanism of laser acceleration of a charged particle is discovered and explained. Particle acceleration with focused beam of superintense ultrashort laser pulse is determined by a combination of ponderomotive forces at rising and falling edges of laser pulse and a longitudinal component of laser electric field. We found that acceleration of electron, which moves along the laser wavevector, is crucially depends on whether or not the electron reaches the region z , zR behind the laser focus (here zR is the Rayleigh length). Interpretation of this effect consists in that the laser longitudinal electric field at the electron trajectory in this region is a unidirectional one (oscillatory in the case of laser linear polarization and slowly varying in the case of laser circular polarization). Due to this effect it is possible to overcome the negative influence of a phase slippage in the particle- wave interaction, which substantially suppresses electron acceleration. We revealed also that the physical reason of a unidirectional influence of laser longitudinal electric field on accelerating electron in the region z , zR consists in the difference in phase velocities of transverse and longitudinal components of a focused laser field. Owing to this mechanism, lasers of ultimate present-day parameters enable electron acceleration up to the energy , , 1 GeV. Moreover, electron acceleration along the laser wavevector (in contrast to techniques currently considered) is not sensitive to field initial phase (there is no bunch effect), it is possible to accelerate slow electrons (electrons need not to be preaccelerated to relativistic velocities), and there are no problems with a removal of accelerated electron from the laser field. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Circularly polarized space-fed microstrip antenna arraysMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Rahul Bhide Abstract A high-gain circularly polarized microstrip antenna array is proposed using space-fed configuration. In planar arrays, the design of feed network to generate circular polarization becomes extremely complex. The proposed configuration eliminates the feed network, which gives high efficiency and gain. Simulated and measured results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2221,2223, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25451 [source] Slits-loaded microstrip antennas for circular polarizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010N. Nasimuddin Abstract Novel diagonally slits-loaded compact microstrip antennas are proposed for circular polarization (CP). A group of four slits is loaded on the square patch radiator for compact antenna size with CP radiation. The slit with unequal sizes loaded on square patch in diagonal directions is used to achieve CP radiation. The combined V -shaped and square slits, diagonally loaded, microstrip antenna is compact when compared with V -shaped slits loaded microstrip antenna. The measured 10-dB return loss and 3-dB axial-ratio bandwidths are 3.55% and 0.82%, respectively, for a combined V -shaped and square slits loaded microstrip patch antenna. The overall size of the antenna is 0.256,0×0.256,0×0.0136,0 at 2.55 GHz. The proposed slits-loaded patch radiator is useful for compact circularly polarized microstrip antenna and array designs. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2043,2049, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25417 [source] A reconfigurable design for bandwidth enhancement of circularly polarized slot antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010Tsung-Hsun Hsieh Abstract A reconfigurable design is proposed to improve the circular polarization (CP) operating bandwidth of an annular-ring slot antenna fed with an L-shaped coupling strip. The design involves four voltage-controlled varactor diodes, which are placed below the slot and symmetrically distributed along the circumference of the slot. When all antenna dimensions remain constant, the CP operating frequency of the slot antenna can be decreased by varying dc voltage values. In addition, theses CP operating frequencies, which are corresponding to different dc voltage values can form a successive frequency band, and the available CP bandwidth is thus improved. Experimental results indicate that with the reconfigurable design, the 3-dB axial-ratio CP bandwidth can be increased by a factor of 4 for the annular-ring slot antenna with a reflector. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1377,1380, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25192 [source] A shorted square-ring slot antenna with a branched slot for the 1575 MHz and 2.4 GHz dual-band operationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009Chin-Long Tsai Abstract A shorted square-ring slot antenna with a branched slot is presented for the 1575 MHz and 2.4 GHz dual-band operations. This proposed antenna can be designed by two steps. First, the shorted square-ring slot antenna is designed for circular polarization in the GPS band. Then, a branched slot is added to the original structure to result linear polarization in the 2.4 GHz band. Because the added branched slot almost has no influence in the GPS band's characteristics, the design rule is very simple. The impedance and axial ratio bandwidths for the GPS band is 23.3% and 4.2%, respectively. Besides, the AR and antenna gain is 1.23 dB and 2.3 dBic at the frequency of 1575 MHz. The impedance bandwidth for the 2.4 GHz band is 4.5% and antenna gain at the center frequency of 2.445 GHz is 2.8 dBi. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 402,405, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24073 [source] A novel reconfigurable circular polarization patch antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2008Jun Ouyang Abstract A novel design of a microstrip patch antenna with switchable branches is proposed to achieve circular polarization diversity. Two branches are incorporated into the patch and two switches are utilized to switch the branches on and off. By turning the switches on or off, this antenna can radiate with either right-handed circular polarization or left-handed circular polarization using the same feeding probe. Experimental results validate this concept. This design demonstrates useful features for wireless communication applications and future planetary missions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1921,1923, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23537 [source] CP-microstrip coplanar patch antenna for satellite receptionMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008Wojciech J. Krzysztofik Abstract A design of a broadband circularly polarized coplanar-square-patch antenna, CSPA, for Iridium satellite reception via handset is proposed and experimentally studied. With the introduction of some asymmetry in the structure to a single-feed coplanar-sqaure-patch microstrip antenna, it is possible to excite two orthogonal degenerate resonant modes for circular polarization (CP) radiation. Experimental results of constructed prototypes show that the obtained 3-dB axial-ratio bandwidths can reach as large as 8.5%. The proposed antenna has a peak antenna gain of about 4.2 dBi, with efficiency 85% for frequencies within the CP. Some prototypes of the proposed CP design CSPA antennas have been implemented and experimental results are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 372,375, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23071 [source] Spiral patch with wideband and circular polarization for millimeter-wave communicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Wei He Abstract In this study, a spiral patch antenna operating millimeter-wave band is proposed. Using this spiral structure, the patch antenna is designed for circular polarization and wideband operation at about 30.8,36.9 GHz for millimeter-wave communication. Simulated and measured results for main parameters such as return loss, impedance bandwidth, radiation patterns, and gains are also discussed herein. The study shows that the modeling of such antennas, with simplicity in designing and feeding, can well meet millimeter-wave wireless communication. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2068,2071, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22648 [source] Spiral antenna with helix loaded for dual circularly polarized bands radiationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2007Can-Hui Chen Abstract A spiral antenna with a helix loaded is investigated in this paper. Through combining the spiral with a helix together, circular polarization can be achieved in dual bands. Since the helix is loaded in the lower part of the spiral, this technique doesn't increase the antenna's volume but at the same time introduces another CP band. The experimental result shows that the lower band and upper band are 4.0% and 62.07% respectively. The characteristics of impedance, current distribution and radiation pattern will also be presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1939,1942, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22596 [source] A wideband circularly polarized microstrip patch antenna for 5,6-GHz wireless LAN applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2005G. Yang Abstract A wideband slotted circularly polarized (CP) patch antenna is introduced for 5,6-GHz WLAN applications. A small 14.6 × 14.6 mm square patch on Duroid 5880 substrate can provide a return-loss bandwidth of 11% and an axial-ratio bandwidth of 8% with a single feed. A possible reconfigurable design achievable using PIN diode or MEMS switches capable of left-hand or right-hand circular polarization is also introduced. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 279,285, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20796 [source] Broadband circularly polarized inverted-L patch antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003Che-Wei Su Abstract An innovative design of a corner-truncated inverted-L patch antenna for achieving circular polarization (CP) operation over a wide bandwidth is presented. The antenna has a thick air-layer substrate; however, it can be easily excited using a probe feed with a short probe pin. CP operation is obtained by selecting an optimal size of the truncated corners, and good impedance matching over a wide bandwidth is obtained by using a beveling technique on the vertical portion of the inverted-L patch. For a prototype constructed for wireless local area network (WLAN) operation in the 2.4-GHz band (2.4,2.484 GHz), the obtained CP bandwidth (3-dB axial ratio) reaches about 7%, and the measured antenna gain is about 8.0 dBi across the CP bandwidth. Details of the antenna design and the experimental results are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 134,136, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10995 [source] Frequency-adjustable circularly polarized dielectric resonator antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2002Chih-Yu Huang Abstract Design of a microstrip-line-feed slot-coupled cylindrical dielectric resonator antenna (DRA) for circular polarization (CP) is investigated experimentally. The occurrence of the two orthogonal near-degenerate resonant modes is mainly excited by a perturbed annular slot that is, a C-shaped slot. The CP resonant frequency can be adjusted by using different slot sizes. Experimental results of the proposed C-slot coupled DRA are presented and discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 211,213, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10419 [source] Quadrifilar helix antenna with parasitic helical stripsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2001Yan Wai Chow Abstract An omnidirectional quadrifilar helix antenna (QHA) with parasitic helical strips for circular polarization (CP) is proposed and experimentally investigated for handheld mobile terminals. This antenna is small in size, low cost, and lightweight. The mutual coupling effect between the grounded helical strips and the feeding helical arms provides a good impedance match, a smaller axial ratio, and wider hemispherical coverage. The impedance bandwidth corresponding to SWR<2 and bandwidth with respect to the axial ratio <3 dB are found to be 39% and 160 MHz at 3.64 GHz, respectively. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 128,130, 2001. [source] PVLAS experiment: some astrophysical consequencesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007Yu. N. Gnedin ABSTRACT The birefringent effects of photon,pseudo-scalar boson (Goldstone) particle mixing in intergalactic magnetic field are calculated for cosmological objects. We use the recent results of PVLAS collaboration that reported recently the observation of a rotation of the polarization plane of light propagating through a transverse static magnetic field. Such result was interpreted as arising due to conversion of photon into pseudo-scalar with coupling strength ga,, 4 × 10,6 GeV,1. This result contradicts to data of stellar evolution that excluded standard axion model and seems to claim existence of supersymmetry (SUSY) pseudo-scalars. We estimate the intergalactic magnetic field magnitude as ,10,16 G based on Hatsemekers et al. observations of extreme-scale alignments of quasar polarization vectors. We analysed some additional results of astronomical observations that could be explained by axion interpretation of the PVLAS data: a sharp steepening of the quasi-stellar object (QSO) continuum shortward of ,1100 Å, observed circular polarization of active galactic nuclei (AGNs) and QSOs, discrepancy between observed intrinsic polarization of stars in the Local Bubble and stellar spectral classification. The observed polarization of stars in the Local Bubble cannot be explained by interstellar origin. [source] Spin orientation of excitons, trions and tetraons in charge tunable InP quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009Yasuaki Masumoto Abstract In the longitudinal magnetic field, photoluminescence (PL) polarization in InP quantum dots (QDs) dramatically changed depending on the number of doped electrons. Under linearly polarized excitation, PL polarizes resonantly at two magnetic fields where bright and dark excitons anticross each other in neutral QDs. On the other hand, PL polarization monotonously increases with the increase of longitudinal magnetic field in one- and two-electron doped QDs, where thermal spin orientation of a photoexcited hole determines the PL polarization of a trion and a tetraon. At low temperatures, however, the electron-hole exchange interaction reduces the thermal spin orientation of holes. In two-electron doped QDs, the anisotropic electron-hole exchange interaction gives small structure in the magnetic-field-dependent circular polarization at the low field region. Time-resolved circular polarization clearly shows the dynamical spin polarization process in charged QDs in the longitudinal magnetic field. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The distribution of circularly polarized light reflection in the Scarabaeoidea (Coleoptera)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010J. DAVID PYE fls The light reflected from many scarab beetles is strongly circularly polarized, a phenomenon that may be unique in nature. Approximately 1500 genera and more than 19 000 species/subspecies of scarab beetles (Scarabaeoidea) in the collection of the Natural History Museum, London, were surveyed with circularly polarizing filters to assess how widespread this effect is and how it relates to colour patterns in the individuals concerned. Over 1100 measurements were made of the strength of the circular polarization, in some cases registering 97%. Circular polarization had been previously described from five subfamilies of Scarabaeidae and, in the present study, was found in three further subfamilies: Phaenomeridinae, Dynastinae and Euchirinae, as well as in the subfamily Ceratocanthinae of the family Hybosoridae, comprising the first records outside the Scarabaeidae. The results may have implications for the taxonomy of the group, for visual discrimination, and for the behaviour of the species themselves. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 585,596. [source] Molecular homochirality and the parity-violating energy difference.CHIRALITY, Issue 2 2008A critique with new proposals Abstract Previous proposals for the origin of molecular homochirality, based on the effect of the weak neutral current (WNC) on enantiomers, and the amplification of the resultant parity-violating energy difference (PVED), are possibly flawed. The additive amplification of PVED in crystals and polymers ("Yamagata hypothesis") cannot lead to detectable levels of optical activity, the original theory apparently overestimating PVED by a factor equal to Avogadro's number. An alternative theory based on the irreversible and spontaneous evolution of a dynamically fluctuating system is apparently impractical. However, the nonlinear amplification of PVED via autocatalytic polymerization may be possible as indicated by a simplified physico-chemical approach. This may also occur during crystallization and melting, and form the basis of the second order asymmetric transformation. (Thus, reported differences in the melting points of enantiomers in several cases may well be real). Also, the preponderance of racemic compounds over conglomerates may be based on the destabilization of the conglomerate by the action of the WNC on the crystalline lattice. The WNC may also be involved in the anomalous scattering of X-rays, which possibly arises from their circular polarization: the current theory would need to be revised accordingly. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source] High-contrast dark resonance in ,+ , ,, optical fieldLASER PHYSICS LETTERS, Issue 10 2004S. V. Kargapoltsev Abstract The amplitude of , resonance in alkali atoms is limited by perturbing cycling transitions in the case of D2 line or by existence of additional trapping states in the case of D1 line. We propose to eliminate these extra trapping states by using two counter-propagating bichromatic fields of orthogonal circular polarizations. The experiment is in accordance with the theoretical proposal. The result refers to small-size cells and is important for applications in miniaturized atomic clocks. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Three-dimensional localization of excitons in the InAs/GaAs wetting layer , magnetospectroscopic studyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2009A. Babinski Abstract Magnetospectroscopic studies of individual excitonic states confined in potential fluctuations in the InAs/GaAs wetting layer (WL) are presented. A neutral exciton and a trion emission have been identified. They split in magnetic field in two components of orthogonal circular polarizations. The respective Zeeman splitting changes linearly with magnetic field up to 10 T. A significant scatter of the effective excitonic g *-factor is observed, reflecting the distribution of sizes and compositions of potential fluctuations in the WL. The distribution affects also diamagnetic shift of the excitonic emission. The observed properties of the excitons are consistent with a picture of shallow quantum dots formed in the WL due to In composition fluctuations. (© 2009 WILEY-VCH Verlag GmbH & Co. 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