A Study On Photonic Crystal Filter And Absorber Based On Metamaterials

Photonic crystals(PCs) have attracted widespread study due to their unusual electromagnetic(EM) properties and capability to manipulate the flow of light. Applications based on PCs, such as filters, fibers, waveguides, lowthreshold lasers, etc., have been proposed. In analogy to the electronic band gaps of semiconductors, PCs possess photonic band gaps(PBG) originating from the interference of the multiple(Bragg) scattering in a periodic dielectric structure. As the Bragg gap formed by normal dielectric is sensitive to the incident angle and polarization, people try to introduce meta-material into PC, such as the PC composed of epsilon-negative(ENG) materials and munegative(MNG) materials. It is demonstrated that stacking alternating layers of ENG materials and MNG materials leads to a type of PBG corresponding to a zero-averaged refractive index. A number of unique properties of zero-n gap on the beam shaping effect has been studied.In contrary to the usual PBG induced by the Bragg scattering, the zero-n gap is insensitive to incident angle and polarization. By the use of the gap, a broadband omnidirectional reflector can be obtained. In the first part of this paper, the features of the gap and the influence of the thickness of the materials on the gap are discussed. Then, attention is focused on the pass band of the meta-material photonic crystals. A comb-like filter can be obtained in the pass band. By changing the number of period, the number of the transmission peak can be changed. Meanwhile, the transmission peak is insensitive to incident angle an polarization. Besides, the defect mode of the meta-material photonic crystals is discussed. By setting appropriate parameters, the comb-like absorption peak can be observed which is also insensitive to the incident angle and polarization.Based on the omnidirectional zero-n gap, we will theoretically investigated a broadband omnidirectional absorber in the second part of this paper, which is realized by heterostructure containing a collision plasma layer and a mirror. A collision plasma layer and an appropriate dielectric layer are put on the top of the PC to obtain a broadband omnidirectional absorption. The half-width and relative bandwidth of the absorption peak for the structure in our paper is much larger than that in Bragg band gap. Because the gap is insensitive to the incident angle and polarization. It is shown to absorb roughly 70% of all available EM wave in a relative omnidirectional absorption bandwidth 244 MHz, corresponding relative bandwidth 32%.Besides the omnidirectional zero-n gap, we will combine the electromagnetic induced absorption(EIA) in metamaterials with PC to realized perfect absorption in the third part of this paper. The EIA in metamaterials is regarded as a defect layer and a dielectric in one period of the PC. Both methods are demonstrated that a perfect absorption peak can be obtained.