Left Handed Materials

Left handed materials (LHM), materials with a negative index of refraction, can in principle focus light without the need for curved surfaces. The first observation of such a "meta-material" (consisting of alternating layers of metal rods and "C" shaped rings lodged on a honeycomb array of printed circuit boards) came three years ago (see Update 476). Then some theorists said it couldn't be done. Now scientists at several labs say it can be done. At last week's meeting of the American Physical Society (APS) in Austin, Texas, two labs reported devising LHMs of their own and demonstrating a negative-index behavior when microwaves were sent into a wedge-shaped LHM "prism." A group from MIT (represented at the meeting by Andrew Houck) said that microwaves entered an LHM sample and, sure enough, the light waves were refracted according to Snell's law, the classic equation for prescribing what happens when light goes from one medium into another, but with a negative sign. The MIT experiment also provides evidence that light from a point source can be focused with a flat rectangular slab of LHM material (see also Houck et al., Physical Review Letters, 4 April 2003). Patanjali Parimi (Northeastern Univ.) also reported at the meeting that his team of scientists had observed negative-index propagation on microwaves through a LHM sample (for background and some simple movies, see http://sagar.physics.neu.edu/).

Two theorists present at the meeting, Clifford Krowne (Naval Research Lab) and Alexandre Pokrovski (Univ. Utah), affirmed that the experimental results had indeed established the existence of working left handed meta-materials but that an earlier criterion thought necessary for LHM behavior, namely that the material's permittivity (a measure of the material's response to an applied electric field) and its permeability (a measure of the material's response to an applied magnetic field) both had to be negative, was not strictly required. Potential applications in the cell-phone industry alone are many: LHM devices would be handy for filtering, steering, and focusing microwaves. Furthermore, one would expect novel optical effects if negative index-of-refraction materials could be extended into the visible light range.