Photonic Band Gap Materials:
A little history behind Photonic Band Gap materials (PBG)?
In 1987, an American physicist and engineer named Eli Yablonovitch and Canadian physics professor from the University of Toronto Canada, Sajeev John constructed artificial structures that then became the concept of PBG material. In order to evaluate this concept they created a 3D prototype diamond lattice in Plexiglas, which is a type of acrylic glass material. With this creation they were able to prove that PBG materials are capable of propagating electromagnetic waves.
What are Photonic Band Gap materials (PBG)?
Photonic band gap materials (PBG), also known as photonic crystals (PC), were formerly introduced as a way to manage the optical properties of certain materials.
PBG materials are artificial, dielectrics that have a periodic composition of permittivity.
It was discovered that we could not only obtain frequency ranges for materials which light cannot propagate but also ranges in which light can propagate, these frequencies also said to be scale dependent. Diminishing the scale of the elementary cell in the periodic lattice causes the frequency ranges to change, making there values higher. As a result of this, we are able to alter a photonic crystal design from the microwave range into the visible or infrared range.
There are 3 band structures (Fig. 1), the 1D, the 2D and the 3D, in which the 1D material has only one ideal direction of wave propagation, the 2D material with 2 ideal directions that behave as an isotropic mirror and finally the 3D material in which behaves as an isotropic mirror for one or more frequency ranges.
Metallic lattices have curious properties while in the microwave domain, such as a prohibited band that ranges from zero frequency to a fp (Plasmon-like) frequency, which is the biggest wavelength of the field that fits the metallic grid. The band is formed by the combination of resonances of the distinct cavities of the crystal structure. The amount of cavities the strength of the combinations also known as coupling are what form the width of the band. The amount of resonance that is allowed in the band is determined by the amount of coupled/combined cavities in the path of the wave propagation. The first metallo-dielectric PBG materials were constructed and formed in 2D or 3D periodicity arrangements by using metallic rods/wires in air, the only down side of these structures were the fact that they are so big in size, they could actually reach an area of 1m3 for a band of 1-5 GHz frequency. Also there were some other considerations that led to the creation of distinctive metallo-dielectric PBG materials, such as the compact uniplanar PBG material and the high impedance, even though new they both use the classic construction methods used in the microwave devices that was created to for microwave applications as well as electronic devices. With the principle of coupled/combination of...