Near-field imaging in the megahertz range by strongly coupled magnetoinductive surfaces: Experiment and ab initio analysis

In this work, the previously reported near-field imaging by two strongly coupled arrays of planar magnetic resonators is further studied. Experiments are performed to clarify the physical mechanisms underlying such an effect. The specific aim of these experiments is to clarify both the role played by magnetoinductive surface waves MISWs and the presence in the device of evanescent Fourier harmonics amplification. In addition to the experimental work, an ab initio theoretical analysis is developed to obtain a first approximation of the above effects. This model assumes that MISWs play the same role as plasmon-polaritons in negative refractive slabs, thus producing amplification of evanescent Fourier harmonics in the device. It also predicts that imaging occurs close to the resonators' resonant frequency, between the passbands for the two MISW branches that can be excited in the lens. Both predictions from the theoretical model are in qualitative agreement with the experimental results. Quantitative agreement can also be obtained if some appropriate additional hypotheses, taking into account the discrete nature of the present device, are included in the model. The reported results suggest the possibility of using this kind of device for imaging in the megahertz range such as in nuclear magnetic resonance imaging.