Columbia Engineering School researchers have developed optical nanostructures to manipulate the refraction index and to completely control dispersion of light.
They have demonstrated that electromagnetic waves can travel from one point to another without any phase accumulation, thus dispersing in the artificial medium as if the medium was absent in space. Researchers have simultaneously observed phase and zero-index for the first time at the infrared wavelength on the chip-scale.
Scientists at Columbia Engineering have worked together with scientists at the Institute of Microelectronics of Singapore and at the University College of London, Brookhaven National Laboratory to make these observations. The study was supervised by associate professor of mechanical engineering, Chee Wei Wong, along with PhD candidate of electrical engineering, Serdar Kocaman, both belonging to Columbia Engineering. Details on the study will be published on the website of Nature Photonics.
The optical phase can be controlled to precision by combining positive and negative refractive indices. All naturally occurring substances feature a positive refractive index. Artificial subwavelength nanostructures were sculptured such that researchers could manipulate the light dispersion to obtain a a negative refractive index in the medium. Following this, researchers combined the negative index medium with a medium of positive refractive index to achieve a complete nanostructure with a zero refraction index.
According to Kocaman, a metamaterial has been developed that has a zero refractive index. He observed that light scatters through the medium as if it were an empty space. The electromagnetic wave’s oscillatory phase does not advance as in a vacuum and this condition is termed as a zero phase delay, he added.
According to Wong, by controlling the light flow, highly directive antennas,self-focused light beams, and hiding or cloaking objects in the small-scale are possible.
Source: http://www.columbia.edu/