1. Shanghai Jiao Tong University, School of Electronic, Information and Electrical Engineering, 3-317 SEIEE Building, 800 Dong Chuan Rd, Shanghai, 200240, P. R. China
2. Auriga Inc., 400 TradeCenter, Ste 5900, Woburn, MA 01801, U.S.A.
3. Wuppertal University, D-42119 Wuppertal, Germany
4. A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, 2 Alikhanian Brothers St., Yerevan 375036, Armenia