A Northwestern University research team has developed a cloaking material that can hide objects from view in the terahertz range. The development could be applied in healthcare, communications and security.
Designed by Cheng Sun, assistant professor of mechanical engineering at the McCormick School of Engineering and Applied Science, the device utilizes gradient-index materials to direct light reflection and refraction. Objects can be identified by humans through color and shape. Light has to be manipulated to neither scatter near the surface of the object nor be absorbed or reflected by the object in order to make the object invisible.
The team created metamaterials in an endeavor to monitor light in the terahertz frequency, which is between infrared and microwaves. The nano-sized, prism-shaped cloaking structure was developed through electronic transfer microstereo-lithography, where a data projector is used to generate an image on a fluid polymer. Light is then used to change the liquid into a thin solid layer. Each of the 220 prism layers has nano-pores, which can alter the refraction of the light. When an object is placed on the bottom layer of the prism, the light seems to be reflected by a flat surface, making the object appear invisible. The research will help develop materials that could control light propagation.
A lot of organic compounds possess a resonant frequency at the terahertz level, enabling them to be identified with a terahertz scanner. This discovery could facilitate biomedical research and security.
The research paper was recently presented at the annual Conference on Lasers and Electro-Optics, CLEO: 2011.
Source: http://www.northwestern.edu