1. Optoelectronics Research Centre (ORC), Physics Unit/Photonics, Faculty of Engineering and Natural Science, Tampere University, Korkeakoulunkatu 3, 33720 Tampere, Finland
2. Robert Bosch GmbH, Robert-Bosch-Campus 1, 71272 Renningen, Germany
3. Department of Physics & Astronomy, The University of New Mexico, 210 Yale Boulevard NE, Albuquerque, New Mexico 87106 ,United States