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METAMATERIALS and NEGATIVE REFRACTION Nandita Aggarwal Laboratory of Applied Optics Ecole Polytechnique de Federal Lausa PowerPoint Presentation
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METAMATERIALS and NEGATIVE REFRACTION Nandita Aggarwal Laboratory of Applied Optics Ecole Polytechnique de Federal Lausanne. Presentation Overview. Introduction to negative refraction Theoretical explanation Experimental verification Different structures as metamaterials SRR structure

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METAMATERIALS and NEGATIVE REFRACTION Nandita Aggarwal Laboratory of Applied Optics Ecole Polytechnique de Federal Lausa


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slide1

METAMATERIALS and NEGATIVE REFRACTION

Nandita Aggarwal

Laboratory of Applied Optics

Ecole Polytechnique de Federal Lausanne

slide2

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
slide3

Reversing light : Negative refraction

Time reversal

Time reversal and

negative refraction

Negative Refraction

(Reversal of spatial evolution of phase)

slide4

Disobeying Snell’s Law: Left handed materials

Light makes negative angle with the normal

Poynting vector has the opposite sign

to the wave vector

slide5

Negative Refraction

Practical demonstration of negative Refraction

slide6

Theoretical Explanation in brief

Assumption: Wavelength used > spacing and size of the unit cell.

Composite can be assumed homogeneous.

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

slide7

Experimental Verification

LHM material (Prism)

Unit cell : 5mm

Operating wavelength : 3cm (8-12 GHz)

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

slide8

Experimental Verification

Refractive index of teflon : 1.4 +- 0.1

Refractive index of LHM : -2.7 +-0.1

slide9

Different Structures as Metamaterials

  • Split Ring Resonators + Metallic Wires
  • S shaped Split Ring Resonators
  • Extended S shape Split Ring Resonator
  • Fish scale
  • Omega type
slide10

Split Ring Resonator + Metallic Wires

Split Ring Resonator

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

slide11

S shaped Split Ring Resonators

Equivalent electrical circuit of SRR

3-D plot of S-shaped SRR

slide12

S shaped Split Ring Resonators

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

slide13

S shaped Split Ring Resonators

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

slide14

S shaped Split Ring Resonators

The real part of the effective permittivity measured for configuration (b) and (c) with the change in value of h.

slide15

Extended S-shaped Split Ring Resonators

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

slide16

Extended S-shaped Split Ring Resonators

Effective Permeability Vs. Frequency

Normal S-Shaped SRR

Extended S-Shaped SRR

slide17

Omega type structures

Picture of metamaterial actually realized and measured

Unit cell

slide18

Omega type structures

Snell refraction experimental results

3-D result with the three axes representing detected power in mW, Frequency in GHz and angle in degrees.

2-D curve extracted at 12.6 GHz from 3-D results.

slide19

Negative refraction in optical regime

Detailed history of development of magnetic resonance frequency

as a function of time

slide20

Applications

  • Superlens
  • Highly directive Antenna
  • Cloaking
slide21

Superlens

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

Propagating waves:

Evanescent waves:

Diffraction limit of the lens:

slide22

Superlens

Negative Refraction Makes a Perfect Lens

  • With this new lens, both propagating and evanescent waves contribute to the resoltuion of the image
  • Enhancement of evanescent waves i.e. amplification (though evanescent waves carry no energy still the results are surprising) of these waves was proven by Sir John Pendry in 2000.
slide23

Superlens

Perfect Lensing in Action

A slab of negative material effectively removes an equal thickness of space for

(A) The far field

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

slide24

Highly Directive Antennas

Geometrical interpretation of the emission of a source inside slab of metamaterial having optical index close to zero

Construction in reciprocal space

slide25

Cloaking

Invisible Man become a reality?

"I still think it is a distant concept, but this latest structure does show

clearly there is a potential for cloaking -- in the science fiction sense – to

become science fact at some point," says Smith.

slide27

Cloaking

Snapshots of time-dependent , steady-state electric field patterns.

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

slide28

References

  • J.B Pendry Physics review Letters, Vol. 85, no. 18 (3966-3969)
  • John B. Pendry and David R. Smith DRS&JBP (final).doc, Physics Today
  • Costas M. Soukoulis, Stefan Linden, Science, Vol 315, (47-49)
  • H.S Chen et al. PIER 51, 231-247, 2005
  • D. Schurig, J.J. Mock, Science, Vol 314 (977-979); 2006