[1] Univ Alabama, Dept Elect & Comp Engn, Tuscaloosa, AL 35487 USA
[2] Columbia Univ, Dept Elect Engn, New York, NY 10027 USA
[3] Dalian Univ Technol, Minist Educ, Key Lab Precis & Nontradit Machining Technol, Dalian 116024, Liaoning, Peoples R China
[4] Dalian Univ Technol, Inst Photoelect Nanosci & Nanotechnol, Dalian 116024, Liaoning, Peoples R China