Light Amplification by Active Meta-mirrors

We consider a scheme of thin films, deposited on periodically modulated amplifying materials. We show that the reflection from such meta-interface can undergo substantial amplification, due to Fano resonances in the thin films. The amplification strongly increases when the Fano waveguiding modes approach the edge of the continuum and degenerate into the leaky surface modes. The study is based on simplified analytical models, as well as on Rigorous Coupled Wave Analysis.