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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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Laboratory of Applied Optics
Ecole Polytechnique de Federal Lausanne
Time reversal and
(Reversal of spatial evolution of phase)
Light makes negative angle with the normal
Poynting vector has the opposite sign
to the wave vector
Practical demonstration of negative Refraction
Assumption: Wavelength used > spacing and size of the unit cell.
Composite can be assumed homogeneous.
µ(eff.) and ε(eff.) are structure dependent.
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
Refractive index of teflon : 1.4 +- 0.1
Refractive index of LHM : -2.7 +-0.1
Split Ring Resonator
Dispersion curve for the parallel polariraztion. Dashed line shows the SRR with wires placed uniformly between them.
Equivalent electrical circuit of SRR
3-D plot of S-shaped SRR
Effective permeability for the S-SRR structure in the case of F1 = F2 = F = 0.3
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
The real part of the effective permittivity measured for configuration (b) and (c) with the change in value of h.
The ES-SRR structure with a period of 2 rings in the z direction and its analytical model
Effective Permeability Vs. Frequency
Normal S-Shaped SRR
Extended S-Shaped SRR
Picture of metamaterial actually realized and measured
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.
Detailed history of development of magnetic resonance frequency
as a function of time
The electric component of the field will be given by some 2D fourier expansion:
Diffraction limit of the lens:
Negative Refraction Makes a Perfect Lens
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
Geometrical interpretation of the emission of a source inside slab of metamaterial having optical index close to zero
Construction in reciprocal space
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.
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