Slow light in metamaterial heterostructures Kosmas L. Tsakmakidis and Ortwin Hess * Advanced Technology Institute and Department of Physics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, United Kingdom ABSTRACT A competent method for slowing and completely stopping light, based on wave propagation along an adiabatically tapered negative-refractive-index metamaterial heterostructure, is presented. It is analytically shown 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. Moreover, 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 corresponding ray analysis that illustrates the trapping of the associated light-ray and the formation of a double light-ray cone (‘optical clepsydra’). This method for trapping photons conceivably opens the way to a multitude of hybrid, optoelectronic devices to be used in ‘quantum information’ processing, communication networks and signal processors, and may herald a new realm of combined metamaterials and slow light research. Keywords: Slow light, metamaterials, negative refractive index, waveguides, adiabatic variation 1. INTRODUCTION A far-reaching development in modern nanophotonics and nanoengineering has been the conception and practical implementation of materials exhibiting simultaneously negative electric permittivity and magnetic permeability, known also as left-handed metamaterials (LH-MMs). Their conceivable strong economic and social impact, owing to their potential applicability in diverse realms of science, such as telecommunications, radars and defence, nanolithography with light, microelectronics, medical imaging, and so on, has lately prompted an overwhelming excitement within the scientific community [1]-[3]. The history of MMs appears to be dating back to the pioneering work of Kock [4] in the late 40’s; while working at Bell Labs with Sergei Schelkunoff, renowned for his “field equivalence principles” and for his work on antennas theory, Kock published a series of works wherein he proposed numerous ideas for constructing lightweight and small-volume “artificial dielectrics”, used as microwave lenses in antenna systems. Amongst others, he studied the response to an incident quasi-static electromagnetic radiation of isolated or regularly-arrayed metallic particles of various shapes, such as spheres, discs, ellipsoids and prolate or oblate spheroids. He concluded that such structures effectively behave as a dielectric medium, whose permittivity ε and permeability μ can be purposely tuned (but not independently of each other) to an arbitrarily large or small, even negative, value by properly arranging the particles in three dimensions, i.e. the optical properties of the medium depended solely on the particles’ geometrical set up, rather than on their own intrinsic behaviour. Kock also showed that a specially-designed structure, which lately has come to be known as “split-ring resonator” (SRR), can be used to independently increase the permeability μ, such that one can reduce or altogether eliminate the diamagnetic nature of the aforementioned composite structures. His work rose considerable interest within the engineering community of the time, with a number of works extending or elaborating on his ideas. Since then, it has been the subject of detailed coverage in standard engineering textbooks [5]. * O.Hess@surrey.ac.uk; phone +44 (0) 1483 682745; fax +44 (0) 1483 686081. Invited Paper Advances in Slow and Fast Light, edited by Selim M. Shahriar, Philip R. Hemmer, John R. Lowell, Proc. of SPIE Vol. 6904, 690405, (2008) · 0277-786X/08/$18 · doi: 10.1117/12.772225 Proc. of SPIE Vol. 6904 690405-1 2008 SPIE Digital Library -- Subscriber Archive Copy