Terahertz Gap

Cloaking became more than a theory in 2006 when Duke University researchers designed split-resonator metamaterials that, capable of negative refraction, could guide microwaves around a “secret” pouch. The waves seemed to curve above, below and around the pouch without being disrupted in their path, as if the pouch were invisible. Since then, Xiang Zhang’s Berkeley group has devised two new metamaterials for cloaking in the visible part of the spectrum, reported in August 2008 in Science and Nature.
Early last year, Shuang Zhang proposed a matter cloak. Not only light, but also matter “waves” would warp around a small, protected, spherical area. Matter waves exist at the quantum level where quantum mechanics blurs the boundaries between the properties of particles and those of waves. If matter can be cloaked from light waves, so too can matter waves be cloaked from matter, Shuang Zhang and his colleagues suggested in March 2008 in Physical Review Letters.
Few have tried to warp T-rays around a sphere because the radiation is so hard to produce in the first place, Tao says. Nonetheless, at the 2008 IEEE International Electron Devices Meeting, the Boston group said it would build a terahertz invisibility cloak. Such a cloak would countervail T-ray screening technology.


2009-04-02 回答