Near-field resonances in diagnostics of multilayered media

A method of the coherent near-field sounding of multilayered dielectric structures is studied. It is based on field measurements with subwavelength probes (emitting and receiving) that are spaced in the near-field zone above the upper layer of the studied structure. It makes possible to achieve a subwavelength resolution at the control of the layers' depth. Especially high resolution can be achieved using the resonant response. The developed approach can be used, for instance, for the monitoring of epitaxy of multilayered heterostructures using SNOM techniques.