'Invisibility Cloak' Created Using Crystals

Zothecula writes "The quest to build a working 'invisibility cloak' generally focuses on the use of metamaterials – artificially engineered materials with a negative refractive index that have already been used to render microscopic objects invisible in specific wavelengths of light. Now, using naturally occurring crystals rather than metamaterials, two research teams working independently have demonstrated technology that can cloak larger objects in the broad range of wavelengths visible to the human eye. PDFs of the two similarly named research papers are available through arXiv.org."