Magnifying superlenses and other applications of plasmonic metamaterials in microscopy and sensing

Over the past century, the resolution of conventional optical microscopes, which rely on optical waves that propagate into the far field, has been limited because of diffraction to a value of the order of a half-wavelength (lambda(0/)2) of the light used. Although immersion microscopes have slightly improved resolution, of the order of lambda(0)/2n, the increased resolution is limited by the small range of refractive indices n of available transparent materials. However, now we are experiencing a quick demolition of the diffraction limit in optical microscopy. In the last few years, numerous nonlinear optical microscopy techniques based on photoswitching and saturation of fluorescence have demonstrated far-field resolution of 20 to 30 nm. In a parallel development, recent progress in metamaterials has demonstrated that artificial optical media can be created, whose use in microscopy can provide resolution that is not determined by the conventional diffraction limit. The resolution of linear immersion microscopes based on such metamaterials is only limited by losses, which can be minimized by appropriate selection of the constituents of the metamaterials used and by the wavelength(s) used for imaging. It is also feasible to compensate for losses by adding gain to the structure. Thus, optical microscopy is quickly moving towards resolution of around 10 nm, which should bring about numerous revolutionary advances in lithography and imaging.