Recently it has become appreciated that near-field optical methods may be used to develop a new form of microscopy with the remarkable feature of subwavelength spatial resolution. The images obtained with such near-field methods, however, are difficult to interpret and are not related in an obvious way to the structure of the sample under study. For this reason, there is substantial interest in developing a solution to the inverse scattering problem in the near field. It turns out that this problem may be solved by an approach which is closely related to that used for solving the inverse problem in diffusion imaging. The connection between these problems arises from a deep analogy between diffusing waves and evanescent waves, since the latter carries information about subwavelength length scales. By exploiting this analogy, we have developed an analytic inverse-scattering procedure that may be used to reconstruct the index of refraction from near-field scattering data. Exp erimental validation of this method is in progress and promises to allow the visualization of molecular detail with light microscopy.
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