External Invisibility Cloak for Multiobjects With Arbitrary Geometries

In this letter, we design an external invisibility cloak that has the cloaking performance for various scattering objects positioned in the outer canceled air layer. The external cloak has an arbitrary geometry, and the “anti-objects” that embedded in the negative index shell can keep the same shape without being geometrically transformed. Compared to the traditional cloak, the external cloak has a finite canceled air layer but does not cover the objects surfaces. The external cloak has a smaller size than the traditional cloak. Simultaneously, the object in the core layer can also be cloaked and see outside situations. This system can produce an illusion image for an object embedded in the core layer.