See also Ultra thin invisibility Cloak Cloaking device Acoustic cloak Magic ring References Bibliography Further reading Cloaking and Invisibility Fact and Fiction by Professor David R. Smith Electrical and Computer Engineering Duke University (May 28, 2006) Three dimensional optical metamaterial with a negative refractive index by Jason Valentine, Shuang Zhang, Thomas Zentgraf, Erick Ulin Avila, Dentcho A. Genov, Guy Bartal, and Xiang Zhang.