A CRYSTAL widely used in the telecommunications industry can refract light in the opposite way to that expected.
Previously physicists have only achieved this effect using specially made arrays of copper rings and wires embedded in fibreglass, which only worked over a narrow range of microwave frequencies. Yong Zhang and his colleagues at the National Renewable Energy Laboratory in Golden, Colorado, say their crystals are much easier to make – and they could work with many frequencies of light.
The team bonded together two pieces of a common industrial crystal called yttrium orthovanadate so that the crystal planes were in mirror…
