Simeon I Bogdanov1, Alexandra Boltasseva1, Vladimir M Shalaev2. 1. School of Electrical and Computer Engineering, Birck Nanotechnology Center, and Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907, USA. 2. School of Electrical and Computer Engineering, Birck Nanotechnology Center, and Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907, USA. shalaev@purdue.edu.