Parity-Time Symmetric Tunnelling

We show that plane waves can fully "tunnel" through a thin metallic layer perforated with a two-dimensional subwavelength array of tiny holes, assisted by a pair of lossy and active sheets in front and behind the screen. The required conditions for eliminating reflections (no back-scattered power) and shadow (no change in the field strength behind the screen) as well for full tunneling of energy are investigated. It is shown that positioning an active layer behind a highly reflective metallic sheet, one can fully recreate the incident wave behind the shield. Finally we show that a parity-time-symmetric pair of a lossy layer in front and an active layer behind the metallic layer makes both forward and backward scattered powers zero.