Controlling light with light at the nanoscale: Backward-wave optical parametric amplification and generation in negative-index metamaterials

Abstract

Negative-index (negative phase) metamaterials (NIMs) form a novel class of electromagnetic media that promises revolutionary breakthroughs in photonics [1]. A significant progress has been achieved recently in the design of bulk multilayer negative-index plasmonic structures [2–3]. The majority of NIMs realized to date consist of metal dielectric nanostructures that have highly controllable magnetic and dielectric responses. The problem, however, is that these structures have losses that are difficult to avoid, especially in the visible range of frequencies. The losses originate from a number of sources. Irrespective of their origin, losses constitute a major hurdle to the practical realization of the unique optical applications of these structures. Therefore, developing efficient loss-compensating techniques is of paramount importance. Herein, we explore the feasibility of the developing of such techniques making use the nonlinear-optical (NLO) response of the NIMs. Nonlinear optics in the NIMs remains so far a less-developed branch of optics. On a fundamental level, the NLO response of nanostructured metamaterials is not completely understood or characterized, and cannot be predicted effectively to date. Nevertheless, the fact of the local-field enhanced nonlinearities attributed to the plasmonic nanostructures is well established and some rough estimates of their magnitude can be done. The feasibility of crafting NIMs with strong NLO responses have been demonstrated in [4]. Unlike natural positive-index materials, the energy flow and the phase velocity are counter-directed in NIMs, which determines their extraordinary linear and NLO propagation properties. Counterintuitive properties of nonlinear propagation processes in NIMs, such as three-wave mixing (TWM) optical parametric amplification (OPA), second harmonic generation and changes in the optical bistability, which are in a stark contrast with their counterparts in natural materials, were shown in [5].