M. Hilke^9,10 and C. Toninelli^1,2,*

• ¹National Institute of Optics [(Consiglio Nazionale delle Ricerche CNR)–INO)], care of European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy
• ²European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, Sesto Fiorentino 50019, Italy
• ³Departamento de Física de la Materia Condensada, Instituto de Ciencia de los Materiales de Sevilla (ICMSE)–Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Sevilla, P. O. Box 1065, Sevilla 41080, Spain
• ⁴Physics Department, University of Naples, Via Cinthia 21, Fuorigrotta 80126, Italy
• ⁵Catalan Institute of Nanoscience and Nanotechnology (ICN2), Consejo Superior de Investigaciones Científicas (CSIC) and Barcelona Institute of Science and Technology (BIST), Universitat Autònoma de Barcelona (UAB) Campus, Bellaterra, Barcelona 08193, Spain
• ⁶Department of Electrical and Photonics Engineering, DTU Electro, Technical University of Denmark, Østeds Plads 343, Kongens Lyngby, DK-2800, Denmark
• ⁷Institución Catalana de Investigación y Estudios Avanzados (ICREA), Passeig Lluis Companys 23, Barcelona 08010, Spain
• ⁸Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Calle Sor Juana Inés de la Cruz 3, Madrid, 28049 Spain
• ⁹Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada
• ¹⁰Department of Physics, University of Florence, Via Sansone 1, Sesto Fiorentino, 50019, Italy

• ^*toninelli@lens.unifi.it
• ^†These authors contributed equally to this work.