By Patricia Daukantas
Most OSA members, I’m sure, are aware that negative-refractive-index metamaterials have been a hot topic of research for the past few years. Although scientists have found success making materials “invisible” to microwaves, several teams have been racing to extend these materials into the optical range – a development that would have much more interesting applications.
This week, two new papers from a California-based team hit the news wires. The researchers, based at the University of California at Berkeley and Lawrence Berkeley National Laboratory, made a prism out of optically negative-index metamaterial that closely resembles layers of tiny fishnets, according to the letter that appeared in Nature.
Xiang Zhang’s group made their metamaterial out of a stack of alternating layers of silver and magnesium fluoride; the size of the “fishnet” cells was on the order of a few hundred nanometers. The scientists tested the prism’s refractive index at near-infrared wavelengths from 1,200 to 1,800 nm and found that the index went to zero at around 1,475 nm.
In the brief Science paper, Zhang and colleagues reported on a different experiment that refracted red light via an aluminum-oxide array of nanometer-sized holes filled with silver. Negative refraction, however, happened only for transverse magnetic polarized light, not for transverse electric polarized light.
Journalistic interest, of course, is driven by the age-old human dream of invisibility, never mind the cloak and cloaking devices in the Harry Potter and “Star Trek” tales. Fortunately, some of the news coverage took pains to explain that practical devices made from negative-index metamaterials are still many years in the future.
2008-08 August, Miscellaneous Optics