Near-field imaging in the megahertz range by strongly coupled magnetoinductive surfaces: theoretical model and experimental validation

In this work, near-field imaging by two strongly coupled arrays of split ring resonators is analyzed. A simple theoretical model is developed to obtain the transfer function of the lens. This model shows that magnetoinductive surface waves (MISWs) play the same role as plasmon-polaritons in negative refractive slabs. In particular, the model predicts that the image is formed near the resonant frequency of the rings, between the pass-bands for the two MISW branches that can be excited in the lens. It also predicts a significant image enhancement when the distance between the source source and the image plane is smaller than twice the lens width. The predictions of the theoretical model are supported by measurements in the radio-frequency range. This suggests the possibility of using this kind of devices to imaging processes in the megahertz range, as for example in magnetic resonance imaging.