Compensating Losses in Doped Negative-Index Metamaterials via Four-Wave Mixing and Quantum Control

All-optical switching from absorption to amplification and wavelength-selective narrowband filtering are shown possible in doped solids based on parametric amplification and quantum interference. The results are discussed in the context of compensation of losses in negative-index metamaterials. ©2007 Optical Society of America OCIS codes: (270.1670) Coherent optical effects, (1904410) Nonlinear optics, parametric processes Absorption is generally recognized now as one of the most challenging problems that needs to be addressed for practical applications of negative-index metamaterials (NIMs) – artificial electromagnetic materials that promise revolutionary breakthrough in photonics. One of the possible approaches is compensating losses by the amplifying centers embedded into a NIM host material to provide amplification due to population inversion [1]. An alternative approach based on optical parametric amplification in NIMs has been proposed in [2], where the precondition is the non-symmetric current-voltage characteristics of NIM’s structural elements that give rise to its quadratic nonlinearity. Here, we investigate a different option that does not require strong nonlinear-optical response by the building blocks of the NIM. Instead, it employs strong resonant nonlinearities inherent to embedded four-level centers (like molecules and ions) and the methods of quantum control attributed to four-wave coupling in resonant schemes. The coupling scheme under investigation (Fig. 1) involves interference between resonant Raman-like and optical parametric amplification-like quantum pathways [3] (and references therein), but does not rely on a coherent population trapping-type of excitation commonly employed in double-Λ schemes of quantum control in solids [4]. The options of spin (ions) and vibration coherence (molecules) ln are analyzed and compared.