快猫短视频

CURIOUS materials that might lead to perfect lenses are under the spotlight again. Two new reports dispute earlier claims that so-called 鈥渓eft-handed鈥� materials can create lenses with ideal properties for focusing light.

A Russian physicist predicted in 1968 that it should be possible to tune a material so that light inside it would 鈥渨ave鈥� in one direction while transmitting energy the other way. Such a material would have a negative refractive index, making light entering it bend in the wrong direction.

Almost two years ago, John Pendry of Imperial College in London showed that such a material could act as a perfect lens. It would amplify 鈥渆vanescent鈥� waves carrying the finest details of an image, which die away in a normal lens. Then another group made a promising left-handed material from arrays of copper rings (快猫短视频, 14 April 2001, p 35), reporting that it had a negative refractive index for microwaves.

Now two teams have poured cold water on the idea. Nicolas Garcia and Manuel Nieto-Vesperinas of the Spanish National Research Council in Madrid calculate that the tiny amount of absorption the materials would inevitably have would degrade the evanescent waves. Prashant Valanju of the University of Texas at Austin and his colleagues go further, saying that materials can鈥檛 have a negative refractive index for light unless it鈥檚 a pure single frequency, which in reality is impossible.

But Pendry says the Texas team is wrong, and that even if there is some absorption, as the Madrid team say, a lens made of a left-handed material should still perform much better than a normal one. 鈥淭he real challenge is to see whether we can realise these materials experimentally,鈥� he says. 鈥淎nything else is a distraction.鈥�