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Electromagnetic Metamaterials
A metamaterial is an artificially structured medium that exhibits electromagnetic properties that can go beyond those found in nature, hence the name meta-materials. A metamaterial’s properties are derived from its structure, rather than the materials it is composed of. As a result, its properties are not necessarily observed in its constituent materials. Metamaterials are made up of a collection of tiny scatterers whose separation is much less than the wavelength of operation, and therefore can be described by the macroscopic electromagnetic parameters: [epsilon] and [mu]. In metamaterials, the role of molecules in conventional dielectrics is played by small metallic or dielectric inclusions dispersed in a host medium.
Due to the emergence of metamaterials in recent years, physical phenomena in both the microwave and optical regimes that were only theorized about a few decades ago are now possible. A few such examples are artificial magnetism and negative refraction. The advent of metamaterials has enabled the development of new devices such as super-resolving lenses, low-profile and miniaturized antennas, and novel couplers, phase shifters and amplifiers.
Photonic/Electromagnetic Bandgap Materials (PBG/EBG)
Electromagnetic bandgap materials are artificially structured materials whose periodicity is on the order of the wavelength of operation, as opposed to metamaterials where the periodicity is subwavelength. These structures can be dielectric or metallo-dielectric in nature. EBG structures exhibit allowed and forbidden bands of propagation. Waves that are allowed to propagate are known as “modes”, while the forbidden bands of wavelengths are called band gaps or stopbands. The bandgaps arise from Bragg scattering within the crystal lattice of the PBG or EBG structure. The term photonic bandgap is reserved for structures that operate at light frequencies while electromagnetic bandgap refers to structures at any frequency of operation.
Current and potential applications of this technology include: novel optical fibers and LEDs, miniature lasers, microwave antennas and reflectors, and optical integrated circuits.