1. Photonics Engineering Group, University of Cantabria, 39005 Santander, Spain
2. CIBER de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, 28029 Madrid, Spain
3. Instituto de Investigación Sanitaria Valdecilla (IDIVAL), 39011 Santander, Spain
4. Electrical Engineering Department, Federal University of Para, Agencia UFPA, P.O. Box 8619, Belem 66075-900, PA, Brazil
5. Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, 00133 Rome, Italy