1. Department of Electronics, Computer Sciences and Systems (DEIS), University of Bologna, Bologna, Italy
2. Department of Civil, Chemical, Environmental, and Materials Engineering, University of Bologna, Bologna, Italy
3. Advanced Research Center on Electronic Systems “Ercole De Castro” (ARCES), University of Bologna, Bologna, Italy
4. Department of Physics, Terahertz/Photonics Group, Goethe University of Frankfurt am Main, Frankfurt, Germany