Sub-cycle switching of a photonic bandstructure via ultrastrong light-matter coupling J.–M. Ménard, M. Porer, A. Leitenstorfer, R. Huber, R. Degl'Innocenti, S. Zanotto, G. Biasiol, L. Sorba and A. Tredicucci EPJ Web of Conferences, 41 (2013) 09009 Published online: 13 March 2013 DOI: 10.1051/epjconf/20134109009