Left-handed materials
DOI: 10.1063/1.4797039
Are now being explored experimentally. LHMs—which do not exist in nature—have a negative index of refraction, n < 0, meaning that light entering such a material at an angle is refracted on the same side of the normal as its incidence. In principle, an LHM with n = −1 can perfectly focus light without any curved surfaces. The first composite LHMs were built three years ago (see Physics Today, May 2000, page 17 , and June 2001, page 9 ), but some aspects of the theory were controversial. At this year’s March meeting of the American Physical Society in Austin, Texas, two more labs reported devising LHMs and beginning to study the bizarre properties of such materials. Andrew Houck from MIT reported that microwaves refracted through a wedge-shaped LHM “prism” indeed obeyed Snell’s law with a negative n: The microwaves never crossed the normal. The MIT group also provided preliminary evidence that light from a point source can be focused with a flat rectangular LHM slab. Technically, only the real part of n must be negative in an LHM. Patanjali Parimi from Northeastern University in Boston reported measurements of both the real and imaginary parts not only of the index of refraction, but also of the permittivity and permeability of an LHM sample in a microwave waveguide. The prediction of perfect focusing can only be realized when the imaginary part of n, which represents absorptive losses, is zero. (
