Effect of interface and disorder on the far-field image in a two-dimensional photonic-crystal-based flat lens

The effects of interface and disorder on the far-field image in a two-dimensional photonic-crystal-based flat lens are investigated by exact multiple-scattering numerical simulation. It is found that the image qualities can be improved by changing the interface structure of the lens such as tuning the dielectric constants of interface layers, adding symmetric cap layers, and introducing optical gain in the surface layers. In general, modifying the interface structure can cause position variation of the image. However, through taking fitted cap layers, the central peaks of the images can be improved in the case without change of the image position. In contrast, the disorder always reduces the intensities of the image peaks and their positions are not affected by it. It is interesting that similar effects of disorder and material absorption on the image qualities are demonstrated.