[1] Taiyuan Univ Technol, Coll Elect & Power Engn, Taiyuan 030024, Peoples R China
[2] Taiyuan Univ Technol, Coll Phys & Optoelect, Minist Educ, Taiyuan 030024, Peoples R China
[3] Taiyuan Univ Technol, Coll Phys & Optoelect, Shanxi Prov Key Lab Adv Transducers & Intelligent, Taiyuan 030024, Peoples R China