Abstract

Optical negative-index metamaterials (NIMs) form a novel class of artificial electromagnetic materials that promise revolutionary breakthrough in photonics and became possible due to fast developments in nanotechnology. Particularly, this is in regard to signal and information processing capabilities and novel concepts of elemental and integrated optical components and devices, which enable smart, adaptive and reconfigurable sensing and image processing. However, to satisfy the causality principle, NIMs must be lossy. Absorption is generally recognized now as one of the most challenging problems that needs to be addressed for numerous applications of these revolutionary artificial electromagnetic materials. Significant efforts of the NIM's community are currently applied towards compensating losses by the amplifying centers embedded into NIM host materials that provide amplification due to population inversion. Herewith, we propose alternative means of compensating losses, producing full transparency, or amplification, or even cavity-free optical oscillation in NIMs. The underlying physical mechanism essentially stems from constructive and destructive nonlinear interference effects (NIE) in the embedded resonant centers, like ions or molecules, controlled by two light beams with frequencies outside the negative-index domain. The proposed scheme of quantum control involves interference between resonant Raman-like and optical parametric amplification (OPA)-like quantum pathways [I] (and references therein), but does not rely on a coherent population trapping-type of excitation commonly employed in double-A schemes of quantum control [2]. We also show that the propagation features of the signal (probe) wave become dramatically different in NIM compared with its counterpart in natural crystals. Counterintuitive features of nonlinear-optical processes under investigations originate from opposite directions of the energy flow and the phase velocity, which is inherent to electromagnetic waves propagating in NIMs [3-7]. The possibility of compensation of losses and generation of counter-propagating entangled right- and left-handed photons controlled by an external laser has been predicted in such materials, even in a cavity-free regime, based on the extraordinary geometry and features of off-resonant OPA in NIMs [6, 7]. Here, we have used for numerical simulations a solution for the set of coupled density-matrix and Maxwell's equations [I] and the double-A model for inhomogeneously broadened optical transitions in Pr:YSO [2], which exhibits very long spin coherence relaxation time in the ground electronic state.

© 2007 IEEE