Excitation of Evanescent Orders by Employing Metallic Metagrating

Evanescent waves have been a perennially fascinating subject due to its exponential decaying nature and non-propagating behavior. Despite being non-propagating, the evanescent fields can act as a hoard of energy in the vicinity of the interface of two mediums, which can be employed in several fields of applications such as sensing and guided wave optics. Such evanescent fields can be excited and modulated by one-dimensional gratings. Therefore, in this work, we have demonstrated excitation of evanescent orders in terahertz metal gratings operating in the subwavelength regime. Further, the evanescent nature of the excited diffracted orders is confirmed by observing the distance-dependent exponential decay.