Compensating losses in positive- and negative-index metamaterials through nonlinear-optical quantum switching

Optical negative-index metamaterials (NIMs) form a novel class of artificial electromagnetic materials. In this paper, we have shown the possibilities of compensation of strong losses in negative- and positive-index materials by two laser beams as well as of wavelength-selective frequency-tunable narrow-band filtering. Such feasibility of quantum switching from strong absorption to amplification via transparency is possible due to nonlinear interference effects accompanied resonant Raman-like and OPA-like processes in doped metamaterials. A possibility of generation of counter-propagating entangled right- and left-handed photons in doped NIMs in cavity-free regimes is investigated.