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 Double Negative Media (DNG) DPS MNGENG DNG SNGpropagation evanescence propagation Isotropic and homogeneous

3 Backward Propagation E H Right-handed Medium k E k H Left-handed Medium SS DPS medium DNG medium

4 Negative Refraction kiki ktkt krkr ii tt rr air kiki ktkt krkr ii tt rr DPS DNG Regular refraction Regular refraction Negative refraction Negative refraction

5 Negative Refraction Index (NRI) Snell’s Law V. G. Veselago

6 Pendry Perfect Lens A B dt-dt Pendry The lens focuses all the “planes waves” radiated by a dipole source (even the evanescent waves), with no phase or amplitude distortion

7 Material Dispersion DNG metamaterials:can be achieved by frequency resonance of a mixture of metallic and/or dielectric particles in a host medium. Electric plasma frequency Electric resonance frequency “Magnetic plasma frequency” Magnetic resonance frequency. Negative permittivity (effect of wires) Negative permeability (effect of rings)

8 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 The Split Ring Resonator (SRR)

10 Waveguide Experiments Metallic rectangular waveguide: TE 01 mode Waveguide miniaturization SWR Gunn b

11 Array 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:

12 Double Negative Media D. R. Smith and S. Schultz, UCSD

13 DNG Waveguides DNG DPS P1P1 P2P2 P2P2 DNG slab waveguide DNG DPS DNG/DPS directional coupler P1P1 P2P2 Back propagation Back propagation

14 Applications DNG Cloaking devices Metamaterial antennas: increased performance and miniaturization