Alberto Naldoni1,2, Vladimir M Shalaev3, Mark L Brongersma4. 1. School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA. 2. Regional Center of Advanced Technologies and Materials, Faculty of Science, Palacký University, Šlechtitelů 11, 78371 Olomouc, Czech Republic. 3. School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA. shalaev@purdue.edu. 4. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.