An optical device that uses metamaterials and optical scattering to “engineer” multiple ghosts — the holy grail of the fields of optical illusions, electromagnetics and radar detection — offers new possibilities for cognitive deception through the control of light-matter behavior. The scientific community has long been enthralled by the thought of creating an illusion that potentially can transform an actual perception into a precontrolled one. So far, researchers experimenting with metamaterials in “ghosting” have not had much success in changing the perception of the real object, and in defining where the “ghost” should appear. They are able only to create one ghost in the same location as the real object. (a) The original metallic object. (b) The metallic object covered by the NUS-designed ghost device, metamorphosing scattering feature of the original object. (c) A shrunk metallic object at the original center with two wing dielectric objects, whose signature is identical to (b). Courtesy of National University of Singapore. Now researchers from National University of Singapore (NUS), Southeast University in Nanjing and the University of Birmingham, England, have developed an optical illusion device capable of creating multiple virtual ghost images from an original object. The geometric shape, position and equivalent material properties of these ghost images can be predesigned and controlled — and are also able to appear in distributed places away from the location of the real object. The device could be used in applications such as defense and security. The investigators are now working to further develop the technique to make larger microwave devices to achieve radar ghosts and aircraft camouflage. “As our work solves several major issues associated with ‘ghost’ illusion, we believe it will pave the way for future applications of advanced optical illusion, camouflage and cloaking — in an interestingly new sense,” said lead researcher Dr. Qiu Cheng-Wei of NUS’s electrical and computer engineering department. “Our work has enormous potential to enhance our ability to mold, harness and perceive wave at will. I believe it can stimulate new thoughts of realizing something extraordinary that is counterintuitive.” The research will be published in Advanced Functional Materials in March. For more information, visit: www.nus.edu.sg