Abstract

It has recently been theoretically demonstrated that guided electromagnetic waves propagating along an adiabatically tapered negative-refractive-index metamaterial (MM) heterostructure can be considerably slowed down and stored by the Trapped-Rainbow method [1]. Here, we shall explain that, in principle, this method simultaneously allows for broad bandwidth operation (since it does not rely on group index resonances), large delay-bandwidth products (since a wave packet can be completely stopped and buffered indefinitely) and high, almost 100%, in/out-coupling efficiencies. By nature, the presented scheme invokes solid-state materials and, as such, is not subject to low-temperature or atomic coherence limitations. A wave analysis, which demonstrates the halting of a monochromatic field component travelling along the heterostructure, is followed by a pertinent ray analysis, which unmistakably illustrates the trapping of the associated light-ray and the formation of a double light-ray cone ('optical clepsydra') at the point where the ray is trapped. We shall explain that this method for stopping light is resilient to the presence of material losses, i.e. even in the presence of high material losses there are still guided electromagnetic modes, characterised by a real propagation constant and complex frequency which can assume a zero group velocity and be excited in a time-domain experiment.

© 2009 IEEE