1. Department of Electrical
and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia (IIT), Via Barsanti, I-73010 Arnesano, Italy
3. Center for Metamaterials and Integrated Plasmonics, Department of
Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, United States