Left-Handed Materials

Left handed materials (LHM) were the hot topic at the recent Progress on Electromagnetics Research Symposium in Boston.

In left-handed materials both the permittivity (basically the response of the material to an external electric field) and the permeability (response to a magnetic field) have negative values. (It's rare for a material to have either negative permittivity or negative permeability, much less both.)

This results in a negative index of refraction; when light falls on a LHM sample it refracts in a direction opposite to that for conventional materials; this "left handed" property makes an LHM a great candidate solid state filter or antenna (see Update 476).

LHM are "metamaterials," consisting of combinations of C-shaped metal rings (split-ring resonators, or SRR) and tiny metal rods. Although there is still some controversy over the theoretical interpretation of left-handed optical effects, several labs now have successfully tested the materials.

So far the split-ring resonators have been planar (they're arranged like parallel miniature printed circuit units slotted into a motherboard) so the optical effects have also been two-dimensional.

But now a group at ETHZ lab in Zurich are close to getting 3D resonators to work, which would allow an LHM to operate in all three dimensions. According to Olivier Martin (martin@ifh.ee.ethz.ch, 41-163-25722) left-handed materials "could change some fundamental concepts in telecommunications," especially for making possible efficient, isotropic, ultra-small antennas. (Gay-Balmaz and Martin, Applied Physics Letters, 29 July 2002)