FILTER MADE OF METAMATERIALS

• US 20140293467A1
• Filed: 10/10/2012
• Published: 10/02/2014
• Est. Priority Date: 10/10/2011
• Status: Active Grant

• Current Assignee: Lamda Guard Technologies Limited
• Original Assignee: Lamda Guard Technologies Limited
• Inventors: Palikaras, George, Kallos, Themos
• Granted Patent: US 10,698,143 B2
• Time in Patent Office: Days
• US Class Current: 359/885
• CPC Class Codes: G02B 1/005 made of photonic crystals or photonic band gap materials photonic band-gap structures or photonic lattices in integrated optics G02B6/1225; photonic band-gap structures or photonic lattices in optical fibres G02B6/02295
• CPC Class Codes: G02B 5/0816 Multilayer mirrors, i.e. having two or more reflecting layers G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/0825 the reflecting layers comprising dielectric materials only
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: G02B 5/20 Filters polarising elements G02B5/30
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence

Abstract

There is provided a filter for filtering electromagnetic radiation, wherein said filter is arranged to transmit electromagnetic radiation of a first predetermined wavelength and to block transmission of electromagnetic radiation of a second, different predetermined wavelength; said filter comprising a first metamaterial. Optionally, the metamaterial may be formed of a plurality of material elements wherein each material element is at least one-dimensional and the size of the material element along each dimension is no greater than the size of the second predetermined wavelength. The filter comprises a second metamaterial arranged to provide second filtering of electromagnetic radiation.

Claims

1. A filter for filtering electromagnetic radiation, said filter comprising a first metamaterial arranged to provide first filtering of electromagnetic radiation and a second metamaterial arranged to provide second filtering of electromagnetic radiation, wherein the first filtering comprises transmitting electromagnetic radiation at a first wavelength and blocking electromagnetic radiation at a second wavelength.

2. A filter as claimed in claim 1 wherein the first metamaterial is arranged to provide the first filtering to electromagnetic radiation incident at a first angle and the second metamaterial is arranged to provide the second filtering to electromagnetic radiation incident at a second angle not equal to the first angle.

3. A filter as claimed in claim 2 wherein the first and/or second angles are first and/or second ranges of angles, respectively.

4. A filter as claimed in claim 3 wherein the first and/or second ranges of angles partially overlap.

5. A filter as claimed in claim 2 wherein the second filtering comprises transmitting electromagnetic radiation at the first wavelength and blocking electromagnetic radiation at the second wavelength.

6. A filter as claimed in claim 1 wherein the second filtering comprises transmitting electromagnetic radiation at the first wavelength and blocking electromagnetic radiation at a third wavelength not equal to the second wavelength.

7. A filter as claimed in claim 1 wherein the first and/or second wavelengths include a bandwidth.

8. A filter as claimed in claim 6 wherein the third wavelength includes a bandwidth.

9. A filter as claimed in claim 1 wherein the first metamaterial comprises a plurality of structural features having a size in one dimension no greater than the second wavelength of the electromagnetic radiation.

10. A filter as claimed in claim 5 wherein the second metamaterial comprises a plurality of structural features having a size in one dimension no greater than the second wavelength of the electromagnetic radiation.

11. A filter as claimed in claim 6 wherein the second metamaterial comprises a plurality of structural features having a size in one dimension no greater than the third wavelength of the electromagnetic radiation.

12. A filter as claimed in claim 9 wherein the first/second metamaterial comprises a plurality of dielectric layers and the structural features are the respective thicknesses of the dielectric layers.

13. A filter as claimed in claim 12 wherein a first dielectric layer in the plurality of dielectric layers has a first refractive index n₁ and a second dielectric layer in the plurality of dielectric layers has a second, different, refractive index n₂ wherein said first and second dielectric layers form a Bragg reflector.

14. A filter as claimed in claim 13 comprising a plurality of said first dielectric layers alternated with a plurality of said second dielectric layers.

15. A filter as claimed in claim 9 wherein the first/second metamaterial comprises an array of material elements and structural features are the material elements.

16. A filter as claimed in claim 15 wherein the material elements are least partially surrounded by a host medium.

17. A filter as claimed in claim 15 wherein the material elements are located in or on a surface of a host medium.

18. A filter as claimed in claim 17 wherein the material elements are at least partially embedded in the host medium.

19. A filter as claimed in claim 15 wherein the material elements are formed from a dielectric or a metallo-dielectric.

20. A filter as claimed in claim 15 wherein the material elements are formed from a metal.

21. A filter as claimed in claim 20 wherein said metal comprises any of:

gold, silver or alumina.

22. A filter as claimed in claim 15 wherein the material elements have a shape that is any of:

spherical, cubical, cylindrical, ellipsoidal, annular, x-shaped, triangular, irregular or rod-like.

23. A filter as claimed in claim 16 wherein the host medium comprises a dielectric material having a relative permittivity of less than or equal to 5.

24. A filter as claimed in claim 15 wherein the plurality of material elements are arranged in a periodic structure in at least two dimensions.

25. A filter as claimed in claim 15 wherein at least one material element in the plurality of material elements comprises a photonic crystal.

26. A filter as claimed in claim 25 wherein the photonic crystal comprises a dielectric material surrounded by air.

27. A filter as claimed in claim 26 wherein the dielectric material comprises a rod having a cross-sectional shape that is any of:

square, cylindrical, triangular or irregular.

28. A filter as claimed in claim 15 wherein the material element includes a perforation or cavity.

29. A filter as claimed in claim 28 wherein the perforation or cavity comprises an air bubble.

30. A filter as claimed in claim 15 wherein at least one material element in the plurality of material elements comprises a liquid crystal.

31. A filter as claimed in claim 30 wherein said liquid crystal is a cholesteric liquid crystal.

32. A filter as claimed in claim 30 wherein the first/second metamaterial includes a layer which comprises a plurality of helices, wherein each helix is formed from rotation of a cholesteric crystal about a propagation axis.

33. A filter as claimed in claim 30 wherein the first/second metamaterial comprises multiple layers of cholesteric liquid crystals, wherein the crystals in each layer have a different respective pitch.

34. A filter as claimed in claim 1 wherein the filter is comprised in a film.

35. A filter as claimed in claim 1 wherein the filter is comprised in or on any of:

a windscreen, a transparent panel, goggles, an eye shield, a contact lens, a glove, a window, or a cockpit.

36. A filter as claimed in claim 1 wherein the filter is arranged to block electromagnetic radiation at the second wavelength regardless of whether said radiation is polarised or unpolarised.

37. A method of fabricating a filter as claimed in any preceding claim 1 comprising selecting the size, shape, material or configuration of the structural features of the first and/or second metamaterial to provide the correct material properties to achieve said transmitting and blocking of electromagnetic radiation.

38. The method of claim 37 wherein the step of fabricating the first and/or second metamaterial comprises using any of:

physical vapour deposition, sputter deposition, polymer implantation, chemical vapour deposition or spin coating.

39. The method of claim 37 wherein the step of fabricating the first and/or second metamaterial comprises a sol-gel process.