Research on light-wave target detection and imaging by using NR-PC flat lens with active impurities

The authors mainly use the two-dimensional finite-difference time-domain method to study the effection on image resolution of target detection and imaging when active impurities are introduced to negative refraction photonic crystals (NR-PC) flat lens. It is demonstrated that because of the influence of the mini-forbidden band and resonance excitation effect, high transmissivity will appear at the resonance frequency of 0.3068(a/lambda) when the light wave goes through the NP-PC lens. Also, the results show that the refocused wave backscattered from a target is significantly stronger than the directly backscattered wave when no NR-PC flat lens is applied. Further studies demonstrated that the introduction of active impurities into NR-PC lens provides improved refocusing and image resolution. In conclusion, the authors' investigation optimises the performance of the focus-scanning scheme, and provides the basis for converting an idealised left-handed materials (LHM) lens into a physically realisable NR-PC flat lens.