Study On The Zero Index Characteristic Of The Hexagonal Lattice Photonic Crystals And Its Optical Application

Using photonic crystals to achieve the zero refractive index materials, on the one hand provides a new idea for the study and application of the zero refractive index materials, on the other hand, the photonic crystal structure is generally arranged by medium column, which has smaller loss then the metal materials. So the zero index materials made by photonic crystals have greater superiority and prospect in applications.In this work, zero refractive index materials achieved by the photonic crystals were studied by using the simulation and the applications of the zero refractive index were discussed. Using the method of the dispersion characteristics analysis, the Dirac point in the center of the Brillouin zone at the hexagonal lattice photonic crystal band structure was found. Then verified using the effective medium theory that at the Dirac frequency both the effective dielectric constant and the effective magnetic permeability of the photonic crystal are zero at the same time, it is proved to a higher degree that this hexagonal photonic crystals can be used to achieve zero refractive index materials.The simulation result about the characteristic of the zero refractive index emerged by the hexagonal photonic crystals was given using the numerical simulation method. Then the concave lens made by the hexagonal lattice photonic crystal was simulated at the Dirac frequency, the far-field subwavelength focusing can be achieved by the lens. Next, in order to improve the effect of the focusing, introducing the anti-reflection structure at the incident surface of the concave lens, the performance of the concave lens was improved a certain extent, which would improve the resolution of the system.The cloaking effect of this structure is susceptible to several factors. For a size fixed array made from the photonic crystals, the cloaking effect which is influenced by the size of the obstacle and the frequency of the incident wave was discussed in this paper.