aggarwal nandita

download aggarwal nandita

of 30

  • date post

    05-Apr-2018
  • Category

    Documents

  • view

    222
  • download

    0

Embed Size (px)

Transcript of aggarwal nandita

  • 8/2/2019 aggarwal nandita

    1/30

    METAMATERIALS and NEGATIVE REFRACTION

    Nandita Aggarwal

    Laboratory of Applied Optics

    Ecole Polytechnique de Federal Lausanne

  • 8/2/2019 aggarwal nandita

    2/30

    Presentation Overview

    Introduction to negative refraction

    Theoretical explanation

    Experimental verification

    Different structures as metamaterials SRR structure

    S-SRR structure

    EX-SRR structure

    Omega type structure

    Negative refraction in optical regime

    Applications Super lenses High directive Antennas

    Cloak invisibility

    References

  • 8/2/2019 aggarwal nandita

    3/30

    Reversing light : Negative refraction

    Timereversal

    NegativeRefraction

    (Reversal ofspatial evolution

    of phase)

    Time reversalandnegativerefraction

  • 8/2/2019 aggarwal nandita

    4/30

    Disobeying Snells Law: Lefthanded materials

    Light makes negative angle with the norma

    Poynting vector has the opposite sign

    to the wave vector

  • 8/2/2019 aggarwal nandita

    5/30

    NegativeRefraction

    Practical demonstration of negative Refraction

  • 8/2/2019 aggarwal nandita

    6/30

    Theoretical Explanationin brief

    Assumption: Wavelength used > spacing and size ofthe unit cell.

    Composite can be assumedhomogeneous.

    (eff.) and (eff.) are structure dependent.

  • 8/2/2019 aggarwal nandita

    7/30

    ExperimentalVerification

    Al plates separation: 1.2 cm

    Radius of circular plates: 15 cm

    Detector was rotated around the circumference of circle in 1.5

    degree steps

    LHM material (Prism)Unit cell : 5mm

    Operating wavelength : 3cm (8-

    12 GHz)

  • 8/2/2019 aggarwal nandita

    8/30

    ExperimentalVerification

    Refractive index of teflon : 1.4+- 0.1

    Refractive index of LHM : -2.7

    +-0.1

  • 8/2/2019 aggarwal nandita

    9/30

    Split Ring Resonators + Metallic Wires

    S shaped Split Ring Resonators

    Extended S shape Split Ring Resonator

    Fish scale

    Omega type

    Different Structures asMetamaterials

  • 8/2/2019 aggarwal nandita

    10/30

    Ring Resonator + Metallic Wires

    Dispersion curve for the parallel polariraztion.Dashed line shows the SRR with wires placeduniformly between them.

    Split RingResonator

  • 8/2/2019 aggarwal nandita

    11/30

    aped Split Ring Resonators

    3-D plot of S-shapedSRR

    Equivalent electrical circuit ofSRR

  • 8/2/2019 aggarwal nandita

    12/30

    aped Split Ring Resonators

    Effective permeability for the S-SRR structure in the case of F1 =F2 = F = 0.3

  • 8/2/2019 aggarwal nandita

    13/30

    aped Split Ring Resonators

    Two unit cells of a periodic arrayed structure (a) A broken rodsarray, (b) A capacitance-enlarged rods array, (c) A S- shaped rods

    array

  • 8/2/2019 aggarwal nandita

    14/30

    aped Split Ring Resonators

    The real part of the effective permittivitymeasured for configuration (b) and (c) withthe change in value of h.

  • 8/2/2019 aggarwal nandita

    15/30

    ded S-shaped Split Ring Resonators

    The ES-SRR structure with a period of 2 rings in the zdirection and its analytical model

  • 8/2/2019 aggarwal nandita

    16/30

    ded S-shaped Split Ring Resonators

    Extended S-ShapedSRR

    Normal S-Shaped SRR

    Effective Permeability Vs.Frequency

  • 8/2/2019 aggarwal nandita

    17/30

    ega type structures

    Unitcell

    Picture of metamaterialactually realized and measured

  • 8/2/2019 aggarwal nandita

    18/30

    ega type structures

    Snell refractionexperimental results

    3-D result with the three axesrepresenting detected power in mW,

    Frequency in GHz and angle in degrees.

    2-D curve extracted at 12.6 GHz f3-D results.

  • 8/2/2019 aggarwal nandita

    19/30

    tive refraction in optical regime

    Detailed history of development of magnetic resonance frequency

    as a function of time

  • 8/2/2019 aggarwal nandita

    20/30

    Applications

    Superlens

    Highly directive

    Antenna

    Cloaking

  • 8/2/2019 aggarwal nandita

    21/30

    Superlens

    The electric component of the field will be given by some 2D fourier

    expansion:

    Propagating waves:

    Evanescent waves:

    Diffraction limit of the lens:

  • 8/2/2019 aggarwal nandita

    22/30

    Superlens

    With this new lens, both propagating and evanescent wavescontribute to the resoltuion of the image

    Enhancement of evanescent waves i.e. amplification (thoughevanescent waves carry no energy still the results aresurprising) of these waves was proven by Sir John Pendry in2000.

    Negative Refraction Makes a Perfect

    Lens

  • 8/2/2019 aggarwal nandita

    23/30

    Superlens

    Perfect Lensing in Action

    A slab of negative material effectively removes an equalthickness of space for

    (A) The far field

    (B) The near field , translating the object into a perfect image

  • 8/2/2019 aggarwal nandita

    24/30

    Highly DirectiveAntennas

    Geometricalinterpretation of theemission of a sourceinside slab of

    metamaterial havingoptical index close tozero

    Construction in reciprocalspace

  • 8/2/2019 aggarwal nandita

    25/30

    Cloaking

    "I still think it is a distant concept, but this latest structure does showclearly there is a potential for cloaking -- in the science fiction sense become science fact at some point," says Smith.

    Invisible Man become a reality?

  • 8/2/2019 aggarwal nandita

    26/30

    Cloaking

  • 8/2/2019 aggarwal nandita

    27/30

    Cloaking

    Snapshots of time-dependent , steady-state electric fieldpatterns.

    Cu cyllinder is cloaked

    A: Simulation of cloak with exact material properties

    B: Simulation with reduced material properties

    C: Experimental measurment of bare conducting cyllinder

    D: Experimental measurments of cloaked conducting cyllinder

  • 8/2/2019 aggarwal nandita

    28/30

    References

    1. J.B Pendry Physics review Letters, Vol. 85, no. 18

    (3966-3969)

    2. John B. Pendry and David R. Smith DRS&JBP

    (final).doc, Physics Today

    3. Costas M. Soukoulis, Stefan Linden, Science, Vol

    315, (47-49)

    4. H.S Chen et al. PIER 51, 231-247, 2005

    5. D. Schurig, J.J. Mock, Science, Vol 314 (977-979);

    2006

  • 8/2/2019 aggarwal nandita

    29/30

    THANK YOU

  • 8/2/2019 aggarwal nandita

    30/30