Meta-material slab with anisotropic permittivity

1. A meta-material slab formed from multiple layers of at least two different compositions stacked in a first direction, the layers of the meta-material slab being such that an evanescent wave propagating in a propagation direction that is perpendicular to the first direction forms a cone-shaped field along an axis extending along the propagation direction.

2. The meta-material slab of claim 1 , wherein the meta-material slap has an effective index of refraction that is determined by geometries of the multiple layers.

3. The meta-material slab of claim 2 , wherein at least two of the multiple layers have different thicknesses.

4. The meta-material slab of claim 3 , wherein a thickness of each layer of the multiple layers is less than a wavelength of an incident light source.

5. The meta-material of claim 1 , wherein the at least two different compositions have different relative permittivities.

6. The meta-material of claim 1 , wherein the at least two different compositions comprise periodic layers of a first material and a second material, the first material comprising a noble metal having a first thickness and a first permittivity tensor that is below a plasmon frequency associated with the core, the second material comprising a dielectric material having a second permittivity tensor that is greater than the first permittivity tensor.

7. The meta-material of claim 1 , wherein the meta-material slab comprises a hemi-cylindrical shape to focus energy.

8. A head comprising a meta-material slab comprising alternating layers of a first material and a second material, wherein the first material has a first permittivity and the second material has a second permittivity that is greater than the first permittivity such that the permittivity tensor of the meta-material has a first component in a first direction and a second component in a second direction, wherein the first component is different from the second component.

9. The head of claim 8 , wherein the first component of the permittivity tensor is a first function of the first permittivity and the second permittivity and the second component of the permittivity tensor is a second function of the first permittivity and the second permittivity, and wherein the first function is different from the second function.

10. The head of claim 9 , wherein the first material and the second material have different thicknesses.

11. The head of claim 10 , wherein each of the different thicknesses are less than a wavelength of light incident on the meta-material slab.

12. The head of claim 9 , wherein the first material comprises a noble metal and the first permittivity is below a plasmon frequency and the second material comprises a dielectric material and the second permittivity is greater than the first permittivity.

13. The head of claim 9 , wherein the first material is selected from a group consisting of aluminum, gold, silver, and copper.

14. The head of claim 8 , wherein the first component of the permittivity tensor comprises a weighted sum of the first permittivity and the second permittivity, with at least one weight in the weighted sum being a ratio of the thickness of one layer to the combined thickness of at least two layers.

15. The head of claim 8 , wherein the meta-material slab is configured to have a hemi-cylindrical shape.

16. An energy focusing device comprising:

at least two meta-material slabs each comprising alternating layers of at least two different materials having different thicknesses and different relative permittivities; and

a core sandwiched between the at least two meta-material slabs.

17. The energy focusing device of claim 16 , wherein the at least-two meta-material slabs direct at least one component of a wave vector associated with an incident wave to form a cone.

18. The energy focusing device of claim 17 , wherein the at least two meta-material slabs compress at least one component of a wave vector to a focused spot.

19. The energy focusing device of claim 16 , wherein the at least two different materials comprise a first material including a noble metal having a first permittivity and a second material formed from a dielectric material having a second permittivity that is greater than the first permittivity.