Achievements and Prospects in Near-Field Subsurface Diagnostics

By now, various methods of near-field diagnostics of subsurface inhomogeneities based on the solution of inverse scattering problems have been developed and demonstrated in experiments. These near-field methods provide a subwavelength (beyond the Rayleigh limit) resolution in tomography and holography of 3D distributed inhomogeneities - as well as in the profiling (retrieval of depth profiles) of one-dimensional subsurface inhomogeneities. Here we present last achievements of these studies: developing the inverse problem theory for frequency dispersive inhomogeneities in multilayer media and its application to monitoring of tissues variations related to breathing and pulse; experimental study of subsurface tomography by measurements with variable source-receiver base, and the statement of inverse scattering problem for targets with nonlinear susceptibility.