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• S-SRR structure• EX-SRR structure• Omega type structure

Negative refraction in optical regime

Applications• Super lenses• High directive Antennas• Cloak invisibility

References

Reversing light : Negative refraction

Time reversal

Negative Refraction

(Reversal of spatial evolution of phase)

Time reversal and negative refraction

Disobeying Snell’s Law: Left handed materials

Light makes negative angle with the normal

Poynting vector has the opposite sign to the wave vector

Negative Refraction

Practical demonstration of negative Refraction

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.

Experimental Verification

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 : 5mmOperating wavelength : 3cm (8-12 GHz)

Experimental Verification

Refractive index of teflon : 1.4 +- 0.1

Refractive index of LHM : -2.7 +-0.1

• Split Ring Resonators + Metallic Wires

• S shaped Split Ring Resonators

• Extended S shape Split Ring Resonator

• Fish scale

• Omega type

Different Structures as Metamaterials

Split Ring Resonator + Metallic Wires

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

Split Ring Resonator

S shaped Split Ring Resonators

3-D plot of S-shaped SRR Equivalent electrical circuit of SRR

S shaped Split Ring Resonators

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

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

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.

Extended S-shaped Split Ring Resonators

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

Extended S-shaped Split Ring Resonators

Extended S-Shaped SRR Normal S-Shaped SRR

Effective Permeability Vs. Frequency

Omega type structures

Unit cellPicture of metamaterial actually realized and measured

Omega type structuresSnell 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.

Negative refraction in optical regime

Detailed history of development of magnetic resonance frequency as a function of time

Applications

• Superlens

• Highly directive Antenna

• Cloaking

Superlens

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

Propagating waves:

Evanescent waves:

Diffraction limit of the lens:

Superlens

• 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.

Negative Refraction Makes a Perfect Lens

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

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

Cloaking

"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.

Invisible Man become a reality?

Cloaking

Cloaking

Snapshots of time-dependent , steady-state electric field patterns.Cu cyllinder is cloakedA: Simulation of cloak with exact material propertiesB: Simulation with reduced material propertiesC: Experimental measurment of bare conducting cyllinder D: Experimental measurments of cloaked conducting cyllinder

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

THANK YOU