Carpet cloak with photonic crystal shield that permits information exchange

Carpet cloaks designed by optical transformation usually include a perfect shield, which exclude the electromagnetic fields from the under cloaked region. Due to the shield, observers in the cloaked area cannot "see" the outside. In this article, we report a flat carpet cloak that permits information exchange with outer environment by using one- or two-dimensional photonic crystal structures as substitutes for the perfect shield. The lateral shifts at the reflecting surface of the effective shields, which make the carpet cloak detectable, are considered and calculated with a Gaussian beam illumination. In order to counteract the lateral shifts, we redesign the parameters of the cloaking slab based on the coordinate transformation. Good agreements have been obtained between the adjusted carpet and ideal carpet with a perfect shield