Gain in Three-Dimensional Metamaterials utilizing Semiconductor Quantum   Structures
  We demonstrate gain in a three-dimensional metal/semiconductor metamaterial by the integration of optically active semiconductor quantum structures. The rolling-up of a metallic structure on top of strained semiconductor layers containing a quantum well allows us to achieve a three-dimensional superlattice consisting of alternating layers of lossy metallic and amplifying gain material. We show that the transmission through the superlattice can be enhanced by exciting the quantum well optically under both pulsed or continuous wave excitation. This points out that our structures can be used as a starting point for arbitrary three-dimensional metamaterials including gain. 
Stephan Schwaiger, Matthias Klingbeil, Jochen Kerbst, Andreas Rottler,   Ricardo Costa, Aune Koitm\"ae, Markus Br\"oll, Chri...
physics.optics cond-mat.mtrl-sci