Zero-index metamaterials for classical and quantum light

Michelle Chalupnik, Olivia Mello, Eliza Cornell +4 more

A. K. Popov, S. A. Myslivets, Vladimir M. Shalaev

Christophe Couteau

Xu Xiao-Hu, Yongqiang Chen, Zhiwei Guo +2 more

In cavity quantum electrodynamics (cQED), how an atom behaves in a cavity is what people care about. The coupling strength (g) between cavity field and atoms plays a fundamental role in various QED effects including Rabi splitting. In the solid-state case, when an atomic-like two-level system such as a single quantum dot (QD) is placed into a cavity, Rabi splitting would occur if g is strong enough. In the classical limit, when a QD in a cavity changes into a classical oscillator, the normal-mode splitting would also take place. It is known that g relies on the local fields at the places of the QDs or classical oscillators inside the cavity. However, for both cases, the traditional cavity modes involved are all in the form of standing waves and the localized fields are position-dependent. To ensure strong coupling between QDs or classical oscillators and photons, they should be placed right at the place where the cavity field is maximum, which is very challenging. How is the positional uncertainty overcome? Recently, the peculiar behaviors of electromagnetic (EM) fields inside zero-index metamaterial (ZIM) in which permittivity and/or permeability are zero have aroused considerable interest. In ZIMs the propagating phase everywhere is the same and the effective wavelength is infinite, which strongly changes the scattering and mode properties of the EM waves. In addition to the above characteristics, the fields in ZIM could be homogeneous as required by Maxwell equations. While the special properties of ZIMs are investigated, the fabrication of ZIMs is widely studied. It is found that a two dimensional (2D) photonic crystal consisting of a square lattice of dielectric rods with accidental degeneracy can behave as a loss-free ZIM at Dirac point. To overcome the positional uncertainty, in this paper we propose a cavity filled with effective zero-index metamaterial (ZIM). When the ZIM is embedded in a cavity, the enhanced homogeneous fields can occur under the resonance condition. Finally, experimental verification in microwave regime is conducted. In the experiments, we utilize a composite right/left-handed transmission line with deep subwavelength unit cell to mimic a ZIM and use a metallic split ring resonator (SRR) as a magnetic resonator whose resonance frequency is determined by structural parameters. The experimental results that in general agree well with the simulations demonstrate nearly position-independent normal-mode splitting.

Nikolay I. Zheludev

Kosmas L. Tsakmakidis, Ortwin G. Hess

Recently there has been a considerable interest in metamaterial waveguide structures capable of dramatically slowing down or, even, completely stopping light. Here, we shall explain in some detail the working principle behind the deceleration and/or stopping of light in metamaterial structures, and review the various, metamaterial-enabled, methods that have been proposed thus far towards achieving such a goal. Further, we will concisely describe how one can construct zero-loss metamaterials over a continuous and broad (but not infinite) range of frequencies, which is an essential prerequisite for any slow-light system. Moreover, it will be explained that inside such waveguide structures light can in principle be stopped (zero group velocity, vg = 0) even in the presence of losses. By nature, metamaterialenabled schemes for stopping/storing light invoke solid-state materials and, as such, are not subject to low-temperature or atomic coherence limitations. Furthermore, these methods simultaneously allow for broad bandwidth operation, since they do not rely on group index resonances; large delay-bandwidth products, since a wave packet can, in principle, be completely stopped and buffered indefinitely; and (for the case, in particular, where a negative-index metamaterial is used) high, almost 100%, in/out-coupling efficiencies. Thus, we conclude that these methods for trapping photons, which can be realised using existing technology, could open the way to a multitude of hybrid optoelectronic devices to be used in 'quantum information' processing, communication networks and signal processors and may conceivably herald a new realm of combined metamaterials and slow light research.