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- 1. 1 METAMATERIALS Metamaterials are artificial engineered composite structures that can be designed to exhibit specific electromagnetic properties not observed in the constituent materials and not commonly found in nature. • What’s a double negative (DNG) medium and how does it work? • Backward waves and negative refraction • Applications
- 2. 2 Double Negative Media (DNG) 0 0 ε ε µ µ = = D E B H 0 0 ε µ > > 0 0ε µ > < 0 0ε µ < > 0 0 ε µ < < DPSDPS MNGMNGENGENG DNGDNG SNGSNGpropagationpropagation evanescenceevanescence propagationpropagation Isotropic and homogeneous
- 3. 3 Backward Propagation E H Right-handed MediumRight-handed Medium kk E kk H Left-handed MediumLeft-handed Medium SS SS = ×S E H DPS medium DNG medium
- 4. 4 Negative Refraction , 0ε µ > , 0ε µ < ki kt kr θi θt θr air ki kt kr θi θt θr air DPS DNG Regular refractionRegular refraction Negative refractionNegative refraction
- 5. 5 Negative Refraction Index (NRI) Snell’s LawSnell’s Law 1 1 2 2sin | |sinn nθ θ= − 2 0n < V. G. VeselagoV. G. Veselago
- 6. 6 Pendry Perfect Lens AA BB dd t-dt-dtt 1n = − PendryPendry The lens focuses all the “planes waves” radiated by a dipole source (even the evanescent waves), with no phase or amplitude distortion
- 7. 7 Material DispersionMaterial Dispersion DNG metamaterials:DNG metamaterials: can be achieved by frequency resonancecan be achieved by frequency resonance of a mixture ofof a mixture of metallic and/or dielectric particles in a host mediummetallic and/or dielectric particles in a host medium.. Electric plasma frequency Electric resonance frequency “Magnetic plasma frequency” Magnetic resonance frequency. 0 2 2 2 2 0 p p e e e ei ω ωε ε ω ω ωγ − = − − 0 2 2 2 2 0 p p m m m mi ω ωµ µ ω ω ωγ − = − − :peω 0 :eω :pmω 0 :mω Negative permittivity (effect of wires) Negative permeability (effect of rings)
- 8. 8 The Split Ring Resonator (SRR)The Split Ring Resonator (SRR) External magnetic field penetrates through the rings and currents are induced. +− −+ Gap prevents currents from flowing around the ring, which considerably increases the resonance frequency of the structure. Metamaterial, which response should be homogeneous on the scale of the wavelength. SRR provides a resonant structure which is much smaller than the resonance wavelength.
- 9. 9 The Split Ring Resonator (SRR)The Split Ring Resonator (SRR)
- 10. 10 Waveguide ExperimentsWaveguide Experiments 2 2 0k a π β εµ = − ÷ Metallic rectangular waveguide: TEMetallic rectangular waveguide: TE0101 modemode Waveguide miniaturizationWaveguide miniaturization SWR Gunn bb
- 11. 11 Array of Metallic WiresArray of Metallic Wires For long wavelengths an array of metallic wires interacts with electromagnetic waves as a plasma, and thus exhibits a negative permittivity below the plasma frequency: 2 2 1 pω ε ω = −
- 12. 12 Double Negative MediaDouble Negative Media D. R. Smith and S. Schultz, UCSD
- 13. 13 DNG WaveguidesDNG Waveguides DNG DPS DPS P1 P2 P2 DNG slab waveguide DNG DPS DNG/DPS directional coupler P1 P2 Back propagationBack propagation
- 14. 14 ApplicationsApplications DNG • Cloaking devices • Metamaterial antennas: increased performance and miniaturization