DOCSLIB.ORG

Computation and Experiment on Linearly and Circularly Polarized Electromagnetic Wave Backscattering by Corner Reflectors in an Anechoic Chamber

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Computation and Experiment on Linearly and Circularly Polarized Electromagnetic Wave Backscattering by Corner Reflectors in an Anechoic Chamber computation Article Computation and Experiment on Linearly and Circularly Polarized Electromagnetic Wave Backscattering by Corner Reflectors in an Anechoic Chamber Mohammad Nasucha 1,2,*, Josaphat T. Sri Sumantyo 1, Cahya E. Santosa 1, Peberlin Sitompul 1, Agus H. Wahyudi 1, Yang Yu 1 and Joko Widodo 1 1 Center for Environmental Remote Sensing, Graduate School of Science and Engineering, Chiba University, Chiba 263-8522, Japan; [email protected] (J.T.S.S.); [email protected] (C.E.S.); [email protected] (P.S.); [email protected] (A.H.W.); aff[email protected] (Y.Y.); [email protected] (J.W.) 2 Department of Informatics, Universitas Pembangunan Jaya, Tangerang Selatan 15413, Indonesia * Correspondence: [email protected]; Tel.: +81-070-4404-4451 Received: 22 August 2019; Accepted: 21 September 2019; Published: 24 September 2019 Abstract: Electromagnetic wave backscattering by corner reflectors in an anechoic chamber is studied using our developed computational tool. The tool applies the Finite-Difference Time-Domain (FDTD) method to simulate the propagation of the wave’s electric and magnetic fields. Experimental measurement in an anechoic chamber is also carried out as a comparison. The two results show agreement, including the finding that the backscatter intensity variation amongst the four circularly polarized modes is significantly smaller than the variation amongst the four linearly polarization modes. Keywords: computation in radar; computation in synthetic aperture radar; backscattering by corner reflectors; simulation on circularly polarized electromagnetic waves 1. Introduction Understanding electromagnetic (EM) wave backscattering by corner reflectors is of interest to radar researchers. In particular, the backscattering of circularly polarized (CP) EM waves is of great interest. To study these CP EM waves, computations can be useful. The articles [1–9] report previously done computations on EM wave distribution in an anechoic chamber, but not in the context of backscattering by corner reflectors or in the context of CP EM waves. These works contributed to the development and performance improvement of the anechoic chamber. The articles [10–16] report computations and analyses on EM wave backscattering by corner reflectors. However, most of the reported computations for EM waves were done for non-polarized and linearly polarized waves. Until today, only [10] reports a computation on circularly polarized EM waves. It used the Method of Moments, and the report did not present any technical details about how the circular polarization was realized. To respond to this situation, our research aims to study circularly polarized EM wave backscattering by corner reflectors in an anechoic chamber through a computation using the Finite-Difference Time-Domain (FDTD) method. There has been no such work reported thus far. As an addition, we did the same computation for linearly polarized (LP) EM waves. An equivalent experiment has also been carried out to obtain a comparison. Computation 2019, 7, 55; doi:10.3390/computation7040055 www.mdpi.com/journal/computation Computation 2019, 7, 55 2 of 17 Computation 2019, 7, x FOR PEER REVIEW 2 of 16 The simulation was done using our developed computational tool, called Anechoic Chamber SimulationThe simulation Tool Version was 1 (AST_V1).done using Both our thedeveloped simulation computational and the experiment tool, called were doneAnechoic for four Chamber target types,Simulation i.e., triangular Tool Version trihedral, 1 (AST_V1). horizontal Both plate the bar,simulation vertical and plate the bar, experiment and sphere, were and done for all for linear four polarizationtarget types, and i.e., alltriangular circular polarizationtrihedral, horizontal modes. plate bar, vertical plate bar, and sphere, and for all linearThe polarization remainder and ofthis all circular articleis polarization arranged as modes. follows: Section2 addresses the method, Section3 reportsThe the remainder results, Section of this4 discussesarticle is arranged the results, as and follows: Section Section5 summarizes 2 addresses the contentthe method, of all sections.Section 3 reports the results, Section 4 discusses the results, and Section 5 summarizes the content of all 2.sections. Method 2.1.2. Method The Measurement Plan The measurement plan is depicted in Figure1. This was the scenario to be followed by both the computation2.1. The Measurement and the experiment.Plan It can be described as follows: The measurement plan is depicted in Figure 1. This was the scenario to be followed by both the i. The cuboid anechoic chamber size shall be 6.5 (length) 4.0 (width) 2.4 m (height). computation and the experiment. It can be described as follows:× × ii. The distance between the transmitter (TX) and the receiver (RX) antennas shall be 0.8 m. i. The cuboid anechoic chamber size shall be 6.5 (length) × 4.0 (width) × 2.4 m (height). iii.ii. TheThe distance distance between between the the transmitter target (corner (TX) and reflector) the receiver and antennas (RX) antennas in the orthogonalshall be 0.8 m. direction iii. Theshall distance be 3.0 between m. the target (corner reflector) and antennas in the orthogonal direction shall iv. beThe 3.0 vectorm. network analyzer (VNA)’s port 1 shall feed signals to the TX antenna. v.iv. TheThe vector RX antenna network shall analyzer feed signals (VNA)’s to port the VNA’s 1 shall portfeed 2.signals to the TX antenna. vi.v. TheThe RX turntable antenna shallshall befeed controlled signals to by the the VNA’s turntable port controller. 2. vii.vi. TheBoth turntable the VNA shall and be the controlled turntable by controller the turntable can be controller. driven by the Personal Computer (PC). viii.vii. BothPhase the shiftersVNA and shall the be turntable provided controller for the TX can and be RX driven antennas by the in Personal the case of Computer circular polarization (PC). viii. Phaseand shallshifters be installedshall be provided correctly for eachthe TX mode, and RX i.e., antennas RX right-handed in the case TX of right-handed circular polarization (RR), RX andleft-handed shall be installed TX right-handed correctly for (LR), each RX mode, left-handed i.e., RX TX right-handed right-handed TX (LR), right-handed or RX left-handed (RR), RX left-handedTX left-handed TX right-handed (LL). Phase (LR), shifters RX will left-handed not be needed TX right-handed for linear polarization (LR), or RX modes,left-handed i.e., RXTX left-handedhorizontal TX(LL). horizontal Phase shifters (HH), RXwill vertical not be TX needed horizontal for (VH),linear RX polarization horizontal TXmodes, vertical i.e., (HV), RX horizontaland RX vertical TX horizontal TX vertical (HH), (VV). RX vertical TX horizontal (VH), RX horizontal TX vertical (HV), ix. andThe RX transmit vertical power TX vertical shall be(VV). 5 dBm for all measurement cases. x.ix. TheThe transmit target shallpower be shall placed be on5 dBm a turntable for all measurement in such a way cases. so that elevation angle θ = 0◦, and be x. Therotated target in shall such be a way placed so that on thea turntable aspect angle in suchφ changes a way fromso that90 elevationto 90 (negative angle θ and= 0°, positive and be − ◦ ◦ rotatedsigns respectivelyin such a way represent so that the the aspect left and angle the rightϕ changes sides from of the –90° target) to 90° with (negative 5◦ increments. and positive xi. signsThe respectively EM wave frequency represent shall the beleft chosen and the in ri suchght sides a way of so the that target) 5λ < withtarget 5° size increments.< 10λ. xi. The EM wave frequency shall be chosen in such a way so that 5λ < target size < 10λ. FigureFigure 1.1. TheThe measurementmeasurement plan. plan. The The pyramidal pyramidal absorbers absorbers shall shall be be placed placed evenly evenly at at the the inner inner sides sides of allof all six six chamber’s chamber’s walls. walls. Definitions of the elevation angle θ and the aspect angle ϕ are explained in Figure 2. The targets were corner reflectors of four different shapes: Trihedral, horizontal bar, vertical bar, and sphere. To make it realistic for practices, every target was chosen to be large enough compared to the wavelength Computation 2019, 7, 55 3 of 17 Definitions of the elevation angle θ and the aspect angle φ are explained in Figure2. The targets Computationwere corner 2019 reflectors, 7, x FOR PEER of four REVIEW diff erent shapes: Trihedral, horizontal bar, vertical bar, and sphere.3 of 16 To make it realistic for practices, every target was chosen to be large enough compared to the wavelength but not too large to be carried in a radar mission. Here Here we we use use the the term term “med “mediumium size” to specify that 5λ < targettarget size size < 1010λλ.. The The targets targets and and their their descriptions descriptions are are listed listed in in Table Table 11.. TheThe horizontalhorizontal andand thethe vertical plate bars are simply the same object, only having didifferentfferent standingstanding orientations.orientations. Figure 2. Definitions of angles used in this work. The elevation angle θ is the angle between the target’s Figure 2. Definitions of angles used in this work. The elevation angle θ is the angle between the facing direction and the horizontal plane. The aspect angle φ is the electromagnetic (EM) wave incident target’s facing direction and the horizontal plane. The aspect angle ϕ is the electromagnetic (EM) wave angle in the azimuth point of view (in other words, the angle between the target’s facing direction and incident angle in the azimuth point of view (in other words, the angle between the target’s facing the vertical plane). Every measurement case in this study shall be done with θ = 0 and –90 φ 90 . direction and the vertical plane). Every measurement case in this study shall be done◦ with◦ θ≤ = 0°≤ and◦ –90° ≤ ϕ ≤ 90°.
Load more

Recommended publications
  • Lab 8: Polarization of Light
    Lab 8: Polarization of Light 1 Introduction Refer to Appendix D for photos of the appara- tus Polarization is a fundamental property of light and a very important concept of physical optics. Not all sources of light are polarized; for instance, light from an ordinary light bulb is not polarized. In addition to unpolarized light, there is partially polarized light and totally polarized light. Light from a rainbow, reflected sunlight, and coherent laser light are examples of po- larized light. There are three di®erent types of po- larization states: linear, circular and elliptical. Each of these commonly encountered states is characterized Figure 1: (a)Oscillation of E vector, (b)An electromagnetic by a di®ering motion of the electric ¯eld vector with ¯eld. respect to the direction of propagation of the light wave. It is useful to be able to di®erentiate between 2 Background the di®erent types of polarization. Some common de- vices for measuring polarization are linear polarizers and retarders. Polaroid sunglasses are examples of po- Light is a transverse electromagnetic wave. Its prop- larizers. They block certain radiations such as glare agation can therefore be explained by recalling the from reflected sunlight. Polarizers are useful in ob- properties of transverse waves. Picture a transverse taining and analyzing linear polarization. Retarders wave as traced by a point that oscillates sinusoidally (also called wave plates) can alter the type of polar- in a plane, such that the direction of oscillation is ization and/or rotate its direction. They are used in perpendicular to the direction of propagation of the controlling and analyzing polarization states.
    [Show full text]
  • Lecture 14: Polarization
    Matthew Schwartz Lecture 14: Polarization 1 Polarization vectors In the last lecture, we showed that Maxwell’s equations admit plane wave solutions ~ · − ~ · − E~ = E~ ei k x~ ωt , B~ = B~ ei k x~ ωt (1) 0 0 ~ ~ Here, E0 and B0 are called the polarization vectors for the electric and magnetic fields. These are complex 3 dimensional vectors. The wavevector ~k and angular frequency ω are real and in the vacuum are related by ω = c ~k . This relation implies that electromagnetic waves are disper- sionless with velocity c: the speed of light. In materials, like a prism, light can have dispersion. We will come to this later. In addition, we found that for plane waves 1 B~ = ~k × E~ (2) 0 ω 0 This equation implies that the magnetic field in a plane wave is completely determined by the electric field. In particular, it implies that their magnitudes are related by ~ ~ E0 = c B0 (3) and that ~ ~ ~ ~ ~ ~ k · E0 =0, k · B0 =0, E0 · B0 =0 (4) In other words, the polarization vector of the electric field, the polarization vector of the mag- netic field, and the direction ~k that the plane wave is propagating are all orthogonal. To see how much freedom there is left in the plane wave, it’s helpful to choose coordinates. We can always define the zˆ direction as where ~k points. When we put a hat on a vector, it means the unit vector pointing in that direction, that is zˆ=(0, 0, 1). Thus the electric field has the form iω z −t E~ E~ e c = 0 (5) ~ ~ which moves in the z direction at the speed of light.
    [Show full text]
  • Understanding Polarization
    Semrock Technical Note Series: Understanding Polarization The Standard in Optical Filters for Biotech & Analytical Instrumentation Understanding Polarization 1. Introduction Polarization is a fundamental property of light. While many optical applications are based on systems that are “blind” to polarization, a very large number are not. Some applications rely directly on polarization as a key measurement variable, such as those based on how much an object depolarizes or rotates a polarized probe beam. For other applications, variations due to polarization are a source of noise, and thus throughout the system light must maintain a fixed state of polarization – or remain completely depolarized – to eliminate these variations. And for applications based on interference of non-parallel light beams, polarization greatly impacts contrast. As a result, for a large number of applications control of polarization is just as critical as control of ray propagation, diffraction, or the spectrum of the light. Yet despite its importance, polarization is often considered a more esoteric property of light that is not so well understood. In this article our aim is to answer some basic questions about the polarization of light, including: what polarization is and how it is described, how it is controlled by optical components, and when it matters in optical systems. 2. A description of the polarization of light To understand the polarization of light, we must first recognize that light can be described as a classical wave. The most basic parameters that describe any wave are the amplitude and the wavelength. For example, the amplitude of a wave represents the longitudinal displacement of air molecules for a sound wave traveling through the air, or the transverse displacement of a string or water molecules for a wave on a guitar string or on the surface of a pond, respectively.
    [Show full text]
  • Physics 212 Lecture 24
    Physics 212 Lecture 24 Electricity & Magnetism Lecture 24, Slide 1 Your Comments Why do we want to polarize light? What is polarized light used for? I feel like after the polarization lecture the Professor laughs and goes tell his friends, "I ran out of things to teach today so I made some stuff up and the students totally bought it." I really wish you would explain the new right hand rule. I cant make it work in my mind I can't wait to see what demos are going to happen in class!!! This topic looks like so much fun!!!! With E related to B by E=cB where c=(u0e0)^-0.5, does the ratio between E and B change when light passes through some material m for which em =/= e0? I feel like if specific examples of homework were done for us it would help more, instead of vague general explanations, which of course help with understanding the theory behind the material. THIS IS SO COOL! Could you explain what polarization looks like? The lines that are drawn through the polarizers symbolize what? Are they supposed to be slits in which light is let through? Real talk? The Law of Malus is the most metal name for a scientific concept ever devised. Just say it in a deep, commanding voice, "DESPAIR AT THE LAW OF MALUS." Awesome! Electricity & Magnetism Lecture 24, Slide 2 Linearly Polarized Light So far we have considered plane waves that look like this: From now on just draw E and remember that B is still there: Electricity & Magnetism Lecture 24, Slide 3 Linear Polarization “I was a bit confused by the introduction of the "e-hat" vector (as in its purpose/usefulness)” Electricity & Magnetism Lecture 24, Slide 4 Polarizer The molecular structure of a polarizer causes the component of the E field perpendicular to the Transmission Axis to be absorbed.
    [Show full text]
  • Optical Rotation and Linear and Circular Depolarization Rates in Diffusively Scattered Light from Chiral, Racemic, and Achiral Turbid Media
    Journal of Biomedical Optics 7(3), 291–299 (July 2002) Optical rotation and linear and circular depolarization rates in diffusively scattered light from chiral, racemic, and achiral turbid media Kevin C. Hadley Abstract. The polarization properties of light scattered in a lateral University of Waterloo direction from turbid media were studied. Polarization modulation Department of Chemistry and synchronous detection were used to measure, and Mueller calcu- Waterloo, Ontario N2L 3G1, Canada lus to model and derive, the degrees of surviving linear and circular I. Alex Vitkin polarization and the optical rotation induced by turbid samples. Poly- Ontario Cancer Institute/University of Toronto styrene microspheres were used as scatterers in water solutions con- Departments of Medical Biophysics and taining dissolved chiral, racemic, and achiral molecules. The preser- Radiation Oncology vation of circular polarization was found to exceed the linear Toronto, Ontario M5G 2M9, Canada polarization preservation for all samples examined. The optical rota- tion induced increased with the chiral molecule concentration only, whereas both linear and circular polarizations increased with an in- crease in the concentrations of chiral, racemic, and achiral molecules. This latter effect was shown to stem solely from the refractive index matching mechanism induced by the solute molecules, independent of their chiral nature. © 2002 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.1483880] Keywords: polarization; multiple scattering; chirality; polarization modulation. Paper JBO TP-14 received Mar. 8, 2002; revised manuscript received Mar. 14, 2002; accepted for publication Mar. 31, 2002. 1 Introduction Optical investigations of turbid media that contain chiral 23–31 Many natural and synthetic systems have disordered proper- components have also been reported.
    [Show full text]
  • Circular Polarization of Fluorescence of Probes Bound to Chymotrypsin
    Proc. Nat. ASad. Sci. USA Vol. 69, No. 3, pp. 769-772, March 1972 Circular Polarization of Fluorescence of Probes Bound to Chymotrypsin. Change in Asymmetric Environment upon Electronic Excitation* (circularly polarized luminescence/proteins/fluoresent probes) JOSEPH SCHLESSINGERt AND IZCHAK Z. STEINBERG Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel Communicated by Harold A. Scheraga, January 13, 197S ABSTRACT The circular polarization of fluorescence excited. The site, strength, rigidity, and geometry of binding is related to the conformational asymmetry of the emitting of a fluorescent probe to a protein molecule may thus molecule in the first singlet excited state in the same way differ that circular dichroism is related to the conformational in the ground and excited states. The use of fluorescence asymmetry of the absorbing molecule in the electronic for the study of the binding and the environment of the ground state. By measurement of these optical pheno- chromophore in the ground state, therefore, involves the mena, the induced asymmetry of two chromophores bound basic assumption that in the case under investigation no to chymotrypsin (EC 3.4.4.5) when in the ground state Was compared with the induced asymmetry of the ligands major changes have occurred in the bound chromophore when in the excited state. The two chromophores studied upon electronic excitation. Detection and examination of such were 2-p-toluidinylnaphthalene-6.sulfonate (TNS), bound changes is therefore of much interest and importance. at a specific site which is not the active site of the protein, In this study, the changes in the interaction of a protein and an anthraniloyl group, bound at the active site of the molecule and an attached extrinsic chromophore caused by enzyme.
    [Show full text]
  • POLARIZERS • SPATIAL LIGHT MODULATORS • WAVEPLATES • LIQUID CRYSTAL DEVICES • OTHER CAPABILITIES Splitter
    POLARIZERS • Dichroic Circular Polarizer Circular polarizers transmit either left‐circular polarized light or right‐circular polarized light for an input beam of any polarization state. When circularly SPATIAL polarized light is reflected, it’s propagation direction reverses, changing left‐circular polarization to right circular polarization and vice‐versa. Therefore the same polarizer that produces circular polarization of the incident beam will block the LIGHT return beam. Achievement of optical isolation using the circular polarizer requires that the reflection be specular and that no significant depolarization or polarization Key Features MODULATORS modification occur in any intervening medium between the reflector and optical • • • isolator. We offer circular polarizers in two basic designs, each for use in air: High isolation ‐ Dichroic Polarizer / Zero‐Order Retarder Large diameters available ‐ Beamsplitting Polarizer / Zero‐Order Retarder Low transmitted wavefront distortion • Meadowlark Optics Dichroic Circular Polarizers consist of a dichroic linear polarizer WAVEPLATES and true zero‐order quarterwave retarder. Precisely aligning the retarder fast axis at 45° to the linear polarization direction ensures optimum performance. Polarization Suite True zero‐order retarders are used in the assembly of our Dichroic Circular • • • Polarizers and tight retardance tolerances contribute to the final performance. Once aligned, both polarizer and retarder materials are laminated between Linear Polarizers • Precision Linear Polarizer optically flat substrates, providing a peak‐to‐valley transmitted wavefront distortion LIQUID of less than λ/5. Anti‐reflection coated windows ensure surface reflection losses High Contrast Linear Polarizer are minimized. Ultra‐High Contrast Linear Polarizer Glan‐Thompson Polarizer CRYSTAL Achievement of the desired polarization effect requires proper orientation of your Ultra Broadband Polarizer Dichroic Circular Polarizer; be sure to position the indicator marking in the MWIR Polarizer direction of beam propagation.
    [Show full text]
  • 20 Polarization
    Utah State University DigitalCommons@USU Foundations of Wave Phenomena Open Textbooks 8-2014 20 Polarization Charles G. Torre Department of Physics, Utah State University, [email protected] Follow this and additional works at: https://digitalcommons.usu.edu/foundation_wave Part of the Physics Commons To read user comments about this document and to leave your own comment, go to https://digitalcommons.usu.edu/foundation_wave/3 Recommended Citation Torre, Charles G., "20 Polarization" (2014). Foundations of Wave Phenomena. 3. https://digitalcommons.usu.edu/foundation_wave/3 This Book is brought to you for free and open access by the Open Textbooks at DigitalCommons@USU. It has been accepted for inclusion in Foundations of Wave Phenomena by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Foundations of Wave Phenomena, Version 8.2 of infinite radius. If we consider an isolated system, so that the electric and magnetic fields vanish sufficiently rapidly at large distances (i.e., “at infinity”), then the flux of the Poynting vector will vanish as the radius of A is taken to infinity. Thus the total electromagnetic energy of an isolated (and source-free) electromagnetic field is constant in time. 20. Polarization. Our final topic in this brief study of electromagnetic waves concerns the phenomenon of polarization, which occurs thanks to the vector nature of the waves. More precisely, the polarization of an electromagnetic plane wave concerns the direction of the electric (and magnetic) vector fields. Let us first give a rough, qualitative motivation for the phenomenon. An electromagnetic plane wave is a traveling sinusoidal disturbance in the electric and magnetic fields.
    [Show full text]
  • Polarization Fundamental Laboratory Experiments
    Polarization Fundamental Laboratory Experiments Ludwig Eichner Thorlabs, Inc. 435 Rout 206, Newton NJ www.thorlabs.om [email protected] Education Systems from Thorlabs, Inc. Providing knowledge for the trade Fundamental Kit EDKPOL1 Manual EDKPOL1-M ver 0.9 (Draft) 1 Laser safety is the avoidance of laser accidents, especially those involving eye injuries. Since even relatively small amounts of laser light can lead to permanent eye injuries, the sale and usage of lasers is typically subject to government regulations. Moderate and high-power lasers are potentially hazardous because they can burn the retina of the eye, or even the skin. To control the risk of injury, various specifications, for example ANSI Z136 in the US and IEC 60825 internationally, define "classes" of laser depending on their power and wavelength. These regulations also prescribe required safety measures, such as labeling lasers with specific warnings, and wearing laser safety goggles when operating lasers. 2 Table of Contents Introduction Safety Overview Polarization Experiments Birefringence Circular Polarization Double Refraction Polarization by Reflection Polarization by Scattering Properties of Sheet Polarizers 3 Experiments Categories Fundamental experiment may be accomplished using the kit consisting selected Thorlabs product line. A combination of product will produce experimental hands on experiments in fundamental physics interrogating polarization. All Educational Series kits contains building blocks to build experiments in that category. Extensive Experiments Categories Extensive categories in Thorlabs product line. Each category is contains extensive building blocks to build experiments in that spans fundamental category. Experiment in this category will be much more detailed and complex. These experiments cannot be completed in a short interval.
    [Show full text]
  • Circular Spectropolarimetric Sensing of Chiral Photosystems in Decaying Leaves
    Circular spectropolarimetric sensing of chiral photosystems in decaying leaves C.H. Lucas Pattya,∗, Luuk J.J. Visserb, Freek Ariesec, Wybren Jan Bumad, William B. Sparkse, Rob J.M. van Spanninga, Wilfred F.M. R¨oling da, Frans Snikb aMolecular Cell Biology, Amsterdam Institute for Molecules, Medicines and Systems, VU Amsterdam, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands bLeiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands cLaserLaB, VU Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands dHIMS, Photonics group, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands eSpace Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA Abstract Circular polarization spectroscopy has proven to be an indispensable tool in photosynthesis research and (bio)-molecular research in general. Oxygenic pho- tosystems typically display an asymmetric Cotton effect around the chlorophyll absorbance maximum with a signal ≤ 1%. In vegetation, these signals are the direct result of the chirality of the supramolecular aggregates. The circular po- larization is thus directly influenced by the composition and architecture of the photosynthetic macrodomains, and is thereby linked to photosynthetic function- ing. Although ordinarily measured only on a molecular level, we have developed a new spectropolarimetric instrument, TreePol, that allows for both laboratory and in-the-field measurements. Through spectral multiplexing, TreePol is capa- ble of fast measurements with a sensitivity of ∼ 1∗10−4 and is therefore suitable of non-destructively probing the molecular architecture of whole plant leaves. arXiv:1701.01297v1 [q-bio.BM] 5 Jan 2017 We have measured the chiroptical evolution of Hedera helix leaves for a period of 22 days.
    [Show full text]
  • Basic Polarization Techniques and Devices
    Basic Polarization Techniques and Devices © 2005 Meadowlark Optics, Inc This application note briefly describes polarized light, retardation and a few of the tools used to manipulate the polarization state of light. Also included are descriptions of basic component combinations that provide common light manipulation tools such as optical isolators, light attenuators, polarization rotators and variable beam splitters. Light Polarization In classical physics, light of a single color is described by an electromagnetic field in which electric and magnetic fields oscillate at a frequency, (ν), that is related to the wavelength, (λ), as shown in the equation c = λν where c is the velocity of light. Visible light, for example, has wavelengths from 400-750 nm. An important property of optical waves is their polarization state. A vertically polarized wave is one for which the electric field lies only along the z-axis if the wave propagates along the y-axis (Figure 1A). Similarly, a horizontally polarized wave is one in which the electric field lies only along the x-axis. Any polarization state propagating along the y-axis can be superposed into vertically and horizontally polarized waves with a specific relative phase. The amplitude of the two components is determined by projections of the polarization direction along the vertical or horizontal axes. For instance, light polarized at 45° to the x-z plane is equal in amplitude and phase for both vertically and horizontally polarized light (Figure 1B). Page 1 of 7 Circularly polarized light is created when one linear electric field component is phase shifted in relation to the orthogonal component by λ/4, as shown in Figure 1C.
    [Show full text]
  • Elliptical Polarization
    Lecture 5: Polarization and Related Antenna Parameters (Polarization of EM fields – revision. Polarization vector. Antenna polarization. Polarization loss factor and polarization efficiency.) 1. Polarization of EM fields. The polarization of the EM field describes the time variations of the field vectors at a given point. In other words, it describes the way the direction and magnitude the field vectors (usually E ) change in time. The polarization is the figure traced by the extremity of the time- varying field vector at a given point. According to the shape of the trace, three types of polarization exist for harmonic fields: linear, circular and elliptical: y y y E E E ω z x z x z x (a) linear polarization (b) circular polarization (c) elliptical polarization Any type of polarization can be represented by two orthogonal linear polarizations, ( EExy, )or(EEHV, ), whose fields are out of phase by an angle δ of L . • δ = π IfL 0 or n , then a linear polarization results. • δπ= = If L /2 (90) and EExy, then a circular polarization results. • In the most general case, elliptical polarization is defined. 1 It is also true that any type of polarization can be represented by a right-hand circular and a left-hand circular polarizations (EELR , ). We shall revise the above statements and definitions, while introducing the new concept of polarization vector. 2. Field polarization in terms of two orthogonal linearly polarized components. The polarization of any field can be represented by a suitable set of two orthogonal linearly polarized fields. Assume that locally a far field propagates along the z-axis, and the field vectors have only transverse components.
    [Show full text]