Single-resonator double-negative metamaterial
Resonances can be tuned in dielectric resonators in order to construct single-resonator, negative-index metamaterials. For example, high-contrast inclusions in the form of metallic dipoles can be used to shift the first electric resonance down (in frequency) to the first magnetic resonance, or alternatively, air splits can be used to shift the first magnetic resonance up (in frequency) near the first electric resonance. Degenerate dielectric designs become especially useful in infrared- or visible-frequency applications where the resonator sizes associated with the lack of high-permittivity materials can become of sufficient size to enable propagation of higher-order lattice modes in the resulting medium.
1. A double-negative metamaterial, comprising a periodic array of single-resonator unit cells, each resonator comprising at least one inclusion in a dielectric structure wherein the at least one inclusion has a different permittivity than the dielectric structure material and wherein the at least one inclusion comprises at least one high-permittivity inclusion, thereby shifting the higher frequency, lowest-order electric resonance of the resonator to a lower frequency, and at least one low-permittivity inclusion, thereby shifting the lower frequency, lowest-order magnetic resonance of the resonator to a higher frequency such that the electric resonance and the magnetic resonance of the resonator are in alignment at an operating frequency, thereby providing a metamaterial having a negative index of refraction.
2. The double-negative metamaterial of claim 1 , wherein the at least one high-permittivity inclusion has an elongated shape.
3. The double-negative metamaterial of claim 2 , wherein the elongated shape comprises a rod or prolate spheroid.
4. The double-negative metamaterial of claim 1 , wherein the at least one high-permittivity inclusion comprises a metallic dipole.
5. The double-negative metamaterial of claim 1 , wherein the at least one low-permittivity inclusion has a thin, pancake-like shape.
6. The double-negative metamaterial of claim 1 , wherein the low-permittivity inclusion comprises a cut plane or oblate spheroid.
7. The double-negative metamaterial of claim 1 , wherein the at least one low-permittivity inclusion comprises an air split, gas-filled gap, vacuum gap, or a dielectric foam.
8. The double-negative metamaterial of claim 1 , wherein the at least one low-permittivity inclusion comprises two or more cut planes placed rotationally about an incident electric field axis and at symmetry angles of each resonator.
9. The double-negative metamaterial of claim 1 , wherein the dielectric structure comprises a spherical or rectangular structure.
10. The double-negative metamaterial of claim 1 , wherein the dielectric structure comprises Zr x Sn 1-x TiO 4 .
11. The double-negative metamaterial of claim 1 , wherein the dielectric structure comprises PbTe or Te.