![]() While there are designs for isotropic negative index metamaterials (NIMs), 46,47 there exists no experimental 3D isotropic optical NIMs suitable for perfect imaging as envisioned by Pendry due to the constraints of nanofabrication and absorptive losses. 17,44,45 However, these superlenses only operate in the electrostatic limit, which restricts the operation to a single polarization of the light in the near field of the superlens. The advent of metamaterials with simultaneously negative permittivity and permeability 41 brought renewed interest in the properties of left-handed materials first proposed by Veselago, 42 which Pendry demonstrated could be applied to sub-diffraction-limited imaging with his “perfect lens.” 15 Pendry’s seminal paper inspired the experimental verification of negative refractive index 43 and “superlenses” that demonstrate sub-diffraction-limited resolution in the near-field. This is the basis for applying near-field optics to imaging beyond the diffraction limit.Īt the turn of the new millennium, imaginative new approaches for controlling electromagnetic waves began to appear for imaging, 15–23 photovoltaics, 24–26 quantum information processing and simulations, 27–31 wireless communications, 32,33 and novel optical materials, 34–40 among many others. Therefore, an obvious approach to imaging beyond the diffraction limit is to access the near-field within a distance z ≪ λ where the evanescent components containing high spatial frequency information are not yet fully attenuated. A simple analysis of optical imaging systems reveals that the Fourier components of an image greater than ω / c evanescently decay along the optical axis. However, the desire to do things such as imaging biomolecular processes in vivo and characterizing subsurface features in nanoelectronics requires us to return to optical methods and find a way to beat the diffraction limit. In contrast to conventional optical microscopy, avoiding the use of photons to gather image information at this length scale means that Abbe’s diffraction limit 1 poses no problem. ![]() The development of technologies such as scanning electron microscopy (SEM), scanning tunneling microscopy (STM), and atomic force microscopy (AFM) offered a dramatic new insight into physical structures at the nanometer scale.
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