Dipartimento di Fisica;
Universitàdi Pavia;
Via A.Bassi 6;
27100 Pavia;
Italy;
Centre for Advanced Photonics and Process Analysis;
Munster Technological University;
Rossa Ave Bishopstown;
Cork;
T12 P928;
Ireland;
Tyndall National Institute;
Lee Maltings Complex Dyke Parade;
Cork;
T12 R5CP;
Ireland;
SUPA;
School of Physics and Astronomy;
University of St.Andrews;
Fife;
KY169SS;
UK;
Present address:École Polytechnique Fédérale de Lausanne;
Photonic Systems Laboratory(PHOSL);
STI-IEL;
Station 11;
Lausanne;
1015;
Switzerland;