Evanescent modes stored in cavity resonators with backward-wave slabs

摘要

As was shown by N. Engheta, electromagnetic fields in two adjacent slabsbounded by two metal walls can satisfy the boundary conditions even if thedistance between the two walls is much smaller than the wavelength. This ispossible if one of the slabs has a negative permeability. Here we show thatthese subwavelength "resonators" resonate only if the permeability of at leastone of the slabs is frequency dependent. Thus, there is no advantage of usingthese structures with "left-handed" slabs as frequency-selective devices.However, we have found that these systems can be in principle used as memorydevices for evanescent fields, because the boundary conditions are identicallysatisfied for all plane evanescent waves inside the cavity. The physicalmeaning and practical limitations for possible realizations are discussed. Theanalysis is supported by FDTD simulations.