Figure 3
Schematic of (a) a superlens, (b) an FSL, (c) a 2D FSL and (d) the hyperlens proposed by Zhang’s group. (e–g) Theoretical comparison of the various optical lenses. Although all of these techniques originate from a similar principle, the technical details are actually quite different. In e, the superlens can only magnify the amplitude of evanescent waves. In f, FSL and 2D FSL extend beyond the conventional function by converting the frequencies to the propagation mode, so that super-resolution signals can readily be captured in the far-field. In g, the hyperlens is a piece of artificial meta-material, in which the wave vectors of evanescent waves reduce until they can propagate in free space. Figure reprinted with permission: a, Ref. 32, ©2005 AAAS; b, Ref. 34, ©2007 ACS; c, Ref. 36, ©2007 ACS; d, Ref. 37, ©2007 AAAS. 2D, two-dimensional; FSL, far-field superlens.
