Subwavelength imaging

Abstract

Abstract The subject of metamaterials started with Veselago’s (1967) introduction of negative refractive index and his simultaneous proposal for a flat lens. We have already discussed the flat-lens family in Section 2.11.4. Its characteristic feature is the existence of a focus inside the lens. The basic principle of its operation has already been shown in Fig. 2.24; for convenience it is shown again in Fig. 5.1. The essential requirement is that the index of refraction is n = 1. The ray trajectories follow then in the geometrical optics approximation. A focal point is brought to a focal point and an object in the object plane is reproduced perfectly in the image plane. This is an obvious advantage of the flat lens. It has no optical axis. A simple illustration in Fig. 5.1 shows an object consisting of three points in the object plane that is perfectly reproduced. At the same time we need to mention a serious disadvantage of the flat lens. It can work only at a single frequency because the n = 1 condition is very strongly frequency-dependent. In traditional imaging language this means that the flat lens has very large chromatic aberration.