Resolution limitations. (a) For good resolution, conventional lenses need a wide aperture to refract rays at large angles θ, but even so, they are limited in resolution by the wavelength used. (b) The missing Fourier components of the image are contained in the near field, which decays exponentially (blue curve) and makes negligible contribution to the image. (c) A lens made from a planar slab of negative-index material not only brings rays to a focus but has the capacity (d) to amplify the near field so that it contributes to the image. Such a negative lens thus removes the wavelength limitation. However, the resonant nature of the amplification places severe demands on materials: They must be very low loss.
Citation: Phys. Today 57, 6, 37 (2004); http://dx.doi.org/10.1063/1.1784272
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