[1] Chinese Acad Sci, State Key Lab Appl Opt, Changchun Inst Opt Fine Mech & Phys, Changchun 130031, Peoples R China
[2] CNR, Ist Microeleelettron Microsist, I-40129 Bologna, Italy
[3] Carlo Gavazzi Space SpA, I-20151 Milan, Italy
[4] INFM Sez Padova, Dipartimento Fis, Padua, Italy