Negative refraction occurs when a beam of light is refracted at an interface, somewhat unexpectedly at first glance, not into the usual quarter-space seen in diagrams in textbooks on electromagnetics and optics, but into the other quarter-space left blank in those diagrams. This phenomenon is perfectly in accord with the principle normally referred to as Snell's Law (usually attributed to Willebrord van Royen van Snel), and had been forecast in 1968 by the Russian physicist Victor Veselago. It was first demonstrated experimentally as recently as 2000 by Sheldon Schultz and David Smith of the University of California at San Diego. At that time John Pendry of Imperial College London showed that one of the remarkable properties of a negatively refracting planar slab is to act as a 'perfect lens', focusing beyond the text book limits set by diffraction of propagating waves, at least within limited frequency ranges.

During the last five years, research on negative refraction has increased exponentially, and on several fronts. Negative refraction by homogeneous materials has been shown to be engendered by the opposition of the phase velocity vector and the time-averaged Poynting vector. Such materials, although fabricated with a microstructure, are effectively homogenous in the frequency regimes wherein negative refraction is observed. The frequency regimes can lie anywhere from ~10 GHz to ~ 100 THz today, and efforts to push to the visible part of the electromagnetic spectrum continue at a fast and furious pace.

Negative refraction by periodically inhomogeneous substances such as photonic crystals has also been demonstrated, theoretically as well as experimentally. There also exists a case of positive refraction by certain crystals that masquerades as negative refraction. Negative refraction of acoustic waves is also being studied.

The experimental confirmation of negative refraction breathed new life in the electromagnetics research community. A host of observable and exploitable effects have been identified, as may be readily noted from the papers included in this Focus Issue on Negative Refraction.

Focus on Negative Refraction Contents

Diffraction by a grating made of an uniaxial dielectric–magnetic medium exhibiting negative refraction
R A Depine and A Lakhtakia

Negative refraction in periodic and random photonic crystals
D Felbacq and G Bouchitte

Imaging of extended objects by a negative refractive index slab
J L Garcia Polmer and M Nieto-Vesperinas

Minimization of losses in a structure having a negative index of refraction
G Dewar

Sub-diffraction imaging with compensating bilayers
D Schurig and D R Smith

A two-dimensional uniplanar transmission-line metamaterial with a negative index of refraction
F Elek and G V Eleftheriades

Negative refraction in 2-D checkerboards by mirror anti-symmetry and 3-D corner lenses
S Guenneau, A C Vutha and S Anantha Ramakrishna

Negative phase velocity in a material with simultaneous mirror-conjugated and racemic chirality characteristics
T G Mackay and A Lakhtakia

Reducing losses and dispersion effects in multilayer metamaterial tunnelling devices
J D Baena, L Jelinek and R Marqués

The challenge of homogenization in metamaterials
C Caloz, A Lai and T Itoh

Investigation of magnetic resonances for different split ring resonator parameters and designs
K Aydin, I Bulu, K Guven, M Kafesaki, C M Soukoulis and E Ozbay

Gyrotropic impact upon negatively refracting surfaces
Allan Boardman, Neil King, Yuriy Rapoport and Larry Velasco

On subwavelength and open resonators involving metamaterials of negative refraction index
Sailing He, Yi Jin, Zhichao Ruan and Jinguo Kuang

Birefringent left-handed metamaterials and perfect lenses for vectorial fields
Alexander A Zharov, Nina A Zharova, Roman E Noskov, Ilya V Shadrivov and Yuri S Kivshar

Compact size highly directive antennas based on the SRR metamaterial medium
Irfan Bulu, Humeyra Caglayan, Koray Aydin and Ekmel Ozbay

Realization of optical superlens imaging below the diffraction limit
Hyesog Lee, Yi Xiong, Nicholas Fang, Werayut Srituravanich, Stephane Durant, Muralidhar Ambati, Cheng Sun and Xiang Zhang

Akhlesh Lakhtakia, Pennsylvania State University, USA and Imperial College, London, UK
Martin McCall, Imperial College, London, UK