Improve Imaging Quality Of Photonic Crystal Slab By Changing Surface Structure Of Photonic Crystal

Veselago put forward the concept of negative refractive index materials in 1968.The negative refractive index materials have many unusual exotic electromagnetic properties,such as negative refraction,reversed Doppler shift and reversed Cerenkov radiation.These special physical properties bring widely application for the negative refractive index materials.However,the negative refractive index materials with electric permittivity ?(27)0 and magnetic permeability ?(27)0 do not exist in nature,so people have been looking for artificial negative refractive index materials.Photonic crystal,a kind of artificial material with periodic dielectric composite structures,at some frequency near the bandgap behave as if they have an effective refractive index.The discovery of negative refraction effect in photonic crystals make many application based on the special physical properties of negative refractive index materials have the possibility of the implementation,the photonic crystal slab lens which can overcome the diffraction limit is one of them.The negative refraction effect,self-collimation effect,near-field scattering effect in photonic crystals play an very important role in photonic crystal slab imaging.The self-collimation effect plays a leading role in the near-field imaging of photonic crystals slab.The negative refraction effect plays a leading role in the non-near-field image.The imaging quality of photonic crystals slab is judged by the intensity and resolution of imaging and the resolution is decided by the full width at half maximum(FWHM)of the image.In this paper,the concept of negative refractive index materials and its special physical properties are introduced firstly.Then,the characteristics of photonic crystals and theory methods used in analyzing photonic crystals are introduced.Finally,the image quality of the two-dimensional photonic crystal slab lens based on negative refraction effect is studied.The stability of the imaging focused by photonic crystals slab is investigated when the position and frequency of source changed.We improve the quality of image focused by photonic crystals slab by changing the surface structure of photonic crystals.Through the exact numerical simulation and physical analysis,it can be found that due to the influences of coupling efficiency and the isotropy of material,the quality of image focused by the original photonic crystals slab is not ideal.The resolution of image could be greatly improved by changing the surface structure of photonic crystals slab.And the stability of the changed photonic crystals slab is better than the original photonic crystals slab when the position of source moved or the frequency of source has a little change.