Active Metamaterials

The outstanding properties of metamaterials open the door of opportunity for a number of exciting practical applications. Fascinating applications such as: perfect lenses that break the diffraction limit of conventional lenses, optical quantum storage, and invisibility cloaking. These dramatic new technological advancements are being severely hindered by the significant loss effects of metamaterials. Overcoming loss limitations is currently one of the most important topics in metamaterials research. Presented in the paper are loss reduction schemes regarding: the geometric shape of metamaterial components, parameter manipulation, and parametric amplification. Active gain is then discussed with experimental and theoretical approaches involving loss compensation of active metamaterials. Next, surface plasmons are introduced discussing the intriguing concepts of spasers and metamaterial lasing spasers. Finally, we move to the opposite direction and consider increasing losses in metamaterials to create near perfect metamaterial absorbers that can find applications in the solar cell industry as well as other fields of science.