  Metamaterials have introduced a whole new world of unusual materials with
functionalities that cannot be attained in naturally occurring material systems
by mimicking and controlling the natural phenomena at subwavelength scales.
However, the inherent absorption losses pose fundamental challenge to the most
fascinating applications of metamaterials. Based on a novel plasmon injection
(PI or \Pi) scheme, we propose a coherent optical amplification technique to
compensate losses in metamaterials. Although the proof of concept device here
operates under normal incidence only, our proposed scheme can be generalized to
arbitrary form of incident waves. The \Pi-scheme is fundamentally different
than major optical amplification schemes. It does not require gain medium,
interaction with phonons, or any nonlinear medium. The \Pi-scheme allows for
loss-free metamaterials. It is ideally suited for mitigating losses in
metamaterials operating in the visible spectrum and is scalable to other
optical frequencies. These findings open the possibility of reviving the early
dreams of making 'magical' metamaterials from scratch.

Optics