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Polarization Properties (polarization + property)
Selected AbstractsLow magnetic fields behavior of photon echo in LuLiF4:Er3+LASER PHYSICS LETTERS, Issue 9 2006V. N. Lisin Abstract It is reported about the first observation and studying of the photon echo in LuLiF4:Er3+. The energy transition is 4I15/2 , 4F9/2 (, = 6536 Å). The density of ErF3 is 0.025 wt%. The operation temperature is 1.9 K. Measurements were spent at low (up to 1200 Oe) and even zero external magnetic fields. It was studied a behavior of the photon echo intensity versus the magnetic field magnitude and direction about the crystal axis C and versus the laser pulse separation t12. It was observed an exponential growth and then, after some plateau, an exponential decreasing of the photon echo intensity as a function of magnetic field with increasing of the magnetic field from zero value. The parameters describing the exponential growth and decreasing are not depended on direction of magnetic field. Value of a magnetic field at which the echo intensity accepts the maximum, and quantity of this maximum decrease with increased the pulse separation t12 and the angle , between the magnetic field and crystal axis. The echo intensity exponentially decreases with increased , . The parameter describing the exponential decreasing is not depended on the magnitude of the field. The echo intensity as a function of pulse separation shows exponential decay. The phase relaxation time is depended on the magnitude and direction of the magnetic field. T2 is equal to 202 ± 16 ns at zero magnetic field. Phenomenological formula is suggested, which qualitatively presents the mentioned dependencies. Polarization properties of the backward photon echo in this crystal are studied also. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Polarization properties of the in vitro old human crystalline lensOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2003Juan M. Bueno Abstract We have studied the spatially resolved polarization properties of the in vitro intact old human crystalline lens (from 56 to 88 years old) by using Mueller-matrix imaging polarimetry. Analysis was performed within an average of 54 h of death. Results show that the overall retardation is small (7° on average) and decreases from the centre of the lens to the periphery. Lenticular birefringence is linear but has a spatial dependence, reducing outwards along the radius. The distribution of azimuthal angle of the birefringent structure of the crystalline lens changes depending on each individual lens. Diattenuation and polarizance were found to be small, however, depolarization was about 35% for the set of lenses studied here. [source] Polarization properties in deep-ultraviolet AlGaN quantum wells with various substrate orientationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010A. Atsushi Yamaguchi Abstract It is known that emission polarization in AlGaN quantum wells (QWs) on c-plane substrates switches from in-plane polarization to c -axis polarization with increasing Al composition. This behaviour is unfavourable for light extraction from c-plane based light emitting diodes (LEDs). Previously, we proposed theoretically that this unfavourable polarization can be changed into favourable in-plane polarization by decreasing well width and/or introduction of compressive strain in c-oriented AlGaN-QWs. In this work, we have investigated the substrate orientation dependence of polarization properties in such AlGaN QWs by numerical calculation using the 6,×,6 k·p Hamiltonian. It is shown that even small inclination of c-plane substrate makes a drastic change in the polarization characteristics and that the use of the vicinal substrates as well as semipolar and nonpolar substrates could be beneficial in improving optical device performance. [source] Scattering behaviour at Merapi volcano (Java) revealed from an active seismic experimentGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2001Ulrich Wegler SUMMARY The seismic structure of the stratovolcano Merapi (Java, Indonesia) was studied using an active seismic experiment. Three 3 km long seismic profiles each consisting of up to 30 three-component seismometers with an interstation distance of 100 m were built up in an altitude range between 1000 and 2000 m above sea level. The detailed study of the seismic properties of the propagation media in active volcanic regions is important to understand the natural seismic signals used for eruption forecasting. The seismic experiment at Merapi therefore concentrates on the heterogeneous structure within a radius of 5 km from the active dome, where the sources of most of the natural volcanic seismic events are located. The cone of Merapi volcano consists of different materials changing on a small scale due to the layering of eruptive material. Additionally, the topography of the erosion valleys leads to an irregular deposition, which cannot be described by a simple 1-D layering. These inhomogeneities have a strong influence on seismic signals. The direct P and S waves are attenuated quickly and show only small amplitudes on seismograms. The energy lost from the direct waves, however, is not changed into heat but scattered and can be observed as seismic coda following the direct waves. The observed seismograms show a spindle-like amplitude increase after the direct P phase. This shape of the envelope can be explained by the diffusion model. According to this model there are so many strong inhomogeneities that the direct wave can be neglected and all energy is concentrated in multiple scattered waves. Besides the envelope, the coherence and polarization properties of the wavefield also indicate strong scattering. Only the first onset shows coherence over a station spacing of 100 m, whereas the late phases carrying the major part of the energy are mainly incoherent. The horizontal components of the seismograms have larger amplitudes than the vertical component, but within the horizontal plane the polarization is almost arbitrary, corresponding to waves arriving from scatterers located arbitrarily in space. As a result of the inversion using the diffusion model we obtain values of the S -wave scattering attenuation coefficient, ,s, and the S -wave intrinsic absorption coefficient, ,i. In the frequency range of 4,20 Hz used in this study the scattering attenuation is at least one order of magnitude larger than the intrinsic absorption (,s,,i). The mean free path of S waves is as low as 100 m (,s,1,100 m). The scattering coefficient is independent of frequency (,s,f0.0), whereas the coefficient of intrinsic attenuation increases with increasing frequency (,i,f1.6). The natural seismic signals at Merapi volcano show similar characteristics to the artificial shots. The first onsets have only small amplitudes and the energy maximum arrives delayed compared to the direct waves. Therefore, these signals appear to be strongly affected by multiple scattering also. [source] Hexagonal Network Organization of Dye-Loaded Zeolite,L Crystals by Surface-Tension Driven Autoassembly,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2006S. Yunus Abstract Highly fluorescent dye-loaded zeolite,L crystals, approximately 1.4,,m long and 650,nm in diameter, are organized in a hexagonal network by a surface-tension-driven autoassembly process. A polydimethylsiloxane (PDMS) film presenting a trigonal ordering of spherical protuberances, including a polystyrene (PS) hexagonal network occupying their interstices, is chosen as the platform for the assembly. The overall wettability and the difference in surface tension between PDMS and PS surfaces are found to offer good conditions for ordering micrometric dye-loaded zeolite,L crystals in a 2D hexagonal network. The resulting film displays a regular hexagonal pattern of polarized fluorescence, reflecting the polarization properties of the dye molecules inserted in the parallel nanochannels of the zeolites. [source] On the polarization properties of the micromaser pumped by the atoms with degenerate levelsLASER PHYSICS LETTERS, Issue 3 2004V. A. Reshetov Abstract The polarization properties of the micromaser field pumped by the atoms with the resonant levels, which are degenerate in the projections of the total angular momentum on the quantization axis, are studied numerically. The standard micromaser operation, when the atoms enter the cavity excited to the upper resonant level, and the micromaser operation under the coherent pump, when the atoms enter the cavity in a superposition of resonant atomic levels, are considered. The treatment is based on the master equation for the density matrix of the micromaser field, which takes into account the degeneracy of atomic levels. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] Tunable flat-top fiber Bragg grating filters fabricated in hydrogen-loaded graded-index multimode fibersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007Hong-Yan Fu Abstract We propose an experimental realization of flat-top filters by fabricating fiber Bragg gratings in graded-index multimode fibers (GI-MMF). Two types of GI-MMFs were used to make this kind of filters, and their spectra and polarization properties were experimentally investigated. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 841,843, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22286 [source] Polarization properties of the in vitro old human crystalline lensOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2003Juan M. Bueno Abstract We have studied the spatially resolved polarization properties of the in vitro intact old human crystalline lens (from 56 to 88 years old) by using Mueller-matrix imaging polarimetry. Analysis was performed within an average of 54 h of death. Results show that the overall retardation is small (7° on average) and decreases from the centre of the lens to the periphery. Lenticular birefringence is linear but has a spatial dependence, reducing outwards along the radius. The distribution of azimuthal angle of the birefringent structure of the crystalline lens changes depending on each individual lens. Diattenuation and polarizance were found to be small, however, depolarization was about 35% for the set of lenses studied here. [source] Polarization properties in deep-ultraviolet AlGaN quantum wells with various substrate orientationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010A. Atsushi Yamaguchi Abstract It is known that emission polarization in AlGaN quantum wells (QWs) on c-plane substrates switches from in-plane polarization to c -axis polarization with increasing Al composition. This behaviour is unfavourable for light extraction from c-plane based light emitting diodes (LEDs). Previously, we proposed theoretically that this unfavourable polarization can be changed into favourable in-plane polarization by decreasing well width and/or introduction of compressive strain in c-oriented AlGaN-QWs. In this work, we have investigated the substrate orientation dependence of polarization properties in such AlGaN QWs by numerical calculation using the 6,×,6 k·p Hamiltonian. It is shown that even small inclination of c-plane substrate makes a drastic change in the polarization characteristics and that the use of the vicinal substrates as well as semipolar and nonpolar substrates could be beneficial in improving optical device performance. [source] Tuning the magnetic properties of ZnCdSe/ZnSe quantum dots by thermal annealingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2006E. Margapoti Abstract Photoluminescence of ZnCdSe/ZnSe quantum dots treated by thermal annealing is investigated in magnetic fields up to 6 T. Thermal annealing leads to considerable changes of the circular polarization properties, which we attribute to different spin relaxation times and exciton lifetimes. A negative diamagnetic shift is observed for quantum dots showing the largest TA-induced shift of 80 meV. Possible origins are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Advanced Technology Solar Telescope: A status reportASTRONOMISCHE NACHRICHTEN, Issue 6 2010S.L. Keil Abstract Magnetic fields control the inconstant Sun. The key to understanding solar variability and its direct impact on the Earth rests with understanding all aspects of these magnetic fields. The Advanced Technology Solar Telescope (ATST) has been design specifically for magnetic remote sensing. Its collecting area, spatial resolution, scattered light, polarization properties, and wavelength performance all insure ATST will be able to observe magnetic fields at all heights in the solar atmosphere from photosphere to corona. After several years of design efforts, ATST has been approved by the U.S. National Science Foundation to begin construction with a not to exceed cost cap of approximately $298M. Work packages for major telescope components will be released for bid over the next several months. An application for a building permit has been submitted (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||