Download Extended S-shaped Split Ring Resonators

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
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SRR structure
S-SRR structure
EX-SRR structure
Omega type structure
Negative refraction in optical regime
Applications
• Super lenses
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High directive Antennas
Cloak invisibility
References
Reversing light : Negative refraction
Time reversal
Time reversal and
negative refraction
Negative Refraction
(Reversal of spatial
evolution of phase)
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
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
Experimental Verification
Refractive index of teflon : 1.4 +- 0.1
Refractive index of LHM : -2.7 +-0.1
Different Structures as Metamaterials
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Split Ring Resonators + Metallic Wires
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S shaped Split Ring Resonators
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Extended S shape Split Ring Resonator
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Fish scale
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Omega type
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.
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
Effective Permeability Vs. Frequency
Extended S-Shaped SRR
Normal S-Shaped SRR
Omega type structures
Unit cell
Picture of metamaterial actually
realized and measured
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.
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
Negative Refraction Makes a Perfect Lens
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With this new lens, both propagating and evanescent waves contribute to
the resoltuion of the image
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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.
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
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.
Cloaking
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
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
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